From 4783ca79b5bd68de5b24f3242425d86fa14e36b4 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Fri, 24 Oct 2025 14:49:37 -0700
Subject: [PATCH 01/17] clippy fixes

---
 Cargo.toml                          |   2 +-
 swiftnav/src/coords/ecef.rs         |   1 +
 swiftnav/src/coords/mod.rs          |  13 +--
 swiftnav/src/edc.rs                 |  11 ++-
 swiftnav/src/reference_frame/mod.rs |   3 +-
 swiftnav/src/signal/code.rs         |   1 +
 swiftnav/src/signal/mod.rs          |   1 +
 swiftnav/src/time/gnss.rs           |  28 +++---
 swiftnav/src/time/mod.rs            |  10 +-
 swiftnav/src/time/utc.rs            | 137 ++++++++++++++--------------
 swiftnav/tests/reference_frames.rs  |   2 +-
 11 files changed, 110 insertions(+), 99 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index 13039ef..f5c4cc1 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,5 +1,5 @@
 [workspace]
 members = [
     "swiftnav",
-    "swiftnav-sys"
+    # "swiftnav-sys"
 ]
diff --git a/swiftnav/src/coords/ecef.rs b/swiftnav/src/coords/ecef.rs
index 2f71387..9774214 100644
--- a/swiftnav/src/coords/ecef.rs
+++ b/swiftnav/src/coords/ecef.rs
@@ -359,6 +359,7 @@ impl MulAssign<&f64> for ECEF {
 mod tests {
     use super::*;
 
+    #[expect(clippy::float_cmp)]
     #[test]
     fn ecef_ops() {
         let a = ECEF::new(1.0, 2.0, 3.0);
diff --git a/swiftnav/src/coords/mod.rs b/swiftnav/src/coords/mod.rs
index 3ba4a72..198f035 100644
--- a/swiftnav/src/coords/mod.rs
+++ b/swiftnav/src/coords/mod.rs
@@ -303,6 +303,7 @@ mod tests {
     const MAX_ANGLE_ERROR_SECS: f64 = 1e-7;
     const MAX_ANGLE_ERROR_RAD: f64 = (MAX_ANGLE_ERROR_SECS / 3600.0).to_radians();
 
+    #[expect(clippy::float_cmp)]
     #[test]
     fn llhrad2deg() {
         let zeros = LLHRadians::default();
@@ -312,11 +313,11 @@ mod tests {
         assert_eq!(0.0, deg.longitude());
         assert_eq!(0.0, deg.height());
 
-        let swift_home: LLHDegrees = [37.779804, -122.391751, 60.0].into();
+        let swift_home: LLHDegrees = [37.779_804, -122.391_751, 60.0].into();
         let rads = swift_home.to_radians();
 
-        assert!((rads.latitude() - 0.659381970558).abs() < MAX_ANGLE_ERROR_RAD);
-        assert!((rads.longitude() + 2.136139032231).abs() < MAX_ANGLE_ERROR_RAD);
+        assert!((rads.latitude() - 0.659_381_970_558).abs() < MAX_ANGLE_ERROR_RAD);
+        assert!((rads.longitude() + 2.136_139_032_231).abs() < MAX_ANGLE_ERROR_RAD);
         assert!(
             rads.height() == swift_home.height(),
             "rads.height() = {}, swift_home.height() = {}",
@@ -339,7 +340,7 @@ mod tests {
     ];
 
     /* Semi-major axis. */
-    const EARTH_A: f64 = 6378137.0;
+    const EARTH_A: f64 = 6_378_137.0;
     /* Semi-minor axis. */
     const EARTH_B: f64 = 6_356_752.314_245_179;
 
@@ -404,7 +405,7 @@ mod tests {
 
     #[test]
     fn llh2ecef2llh() {
-        for llh_input in LLH_VALUES.iter() {
+        for llh_input in &LLH_VALUES {
             let llh_input: LLHRadians = llh_input.into();
             let llh_output = llh_input.to_ecef().to_llh();
 
@@ -425,7 +426,7 @@ mod tests {
 
     #[test]
     fn ecef2llh2ecef() {
-        for ecef_input in ECEF_VALUES.iter() {
+        for ecef_input in &ECEF_VALUES {
             let ecef_input: ECEF = ecef_input.into();
             let ecef_output = ecef_input.to_llh().to_ecef();
 
diff --git a/swiftnav/src/edc.rs b/swiftnav/src/edc.rs
index 1171760..c593e3b 100644
--- a/swiftnav/src/edc.rs
+++ b/swiftnav/src/edc.rs
@@ -332,6 +332,7 @@ mod tests {
     const TEST_DATA: &[u8] = "123456789".as_bytes();
 
     /// Helper function to append a CRC-24Q value as 3 bytes (big-endian) to a buffer
+    #[expect(clippy::cast_possible_truncation)]
     fn append_crc24q(data: &mut Vec<u8>, crc: u32) {
         data.push((crc >> 16) as u8);
         data.push((crc >> 8) as u8);
@@ -365,9 +366,9 @@ mod tests {
 
         /* Test value taken from python crcmod package tests, see:
          * http://crcmod.sourceforge.net/crcmod.predefined.html */
-        let crc = compute_crc24q(TEST_DATA, 0xB704CE);
+        let crc = compute_crc24q(TEST_DATA, 0x00B7_04CE);
         assert!(
-            crc == 0x21CF02,
+            crc == 0x0021_CF02,
             "CRC of \"123456789\" with init value 0xB704CE should be 0x21CF02, not {}",
             crc
         );
@@ -403,7 +404,7 @@ mod tests {
         #[test]
         fn prop_crc_stays_within_24_bits(data in prop::collection::vec(any::<u8>(), 0..1000), init in any::<u32>()) {
             let crc = compute_crc24q(&data, init);
-            prop_assert!(crc <= 0xFFFFFF, "CRC result 0x{:08X} exceeds 24-bit maximum", crc);
+            prop_assert!(crc <= 0x00FF_FFFF, "CRC result 0x{:08X} exceeds 24-bit maximum", crc);
         }
 
         /// Property: Incremental CRC calculation equals full calculation.
@@ -432,10 +433,10 @@ mod tests {
         #[test]
         fn prop_crc_initial_value_masked(data in prop::collection::vec(any::<u8>(), 0..100), init in any::<u32>()) {
             let crc1 = compute_crc24q(&data, init);
-            let crc2 = compute_crc24q(&data, init & 0xFFFFFF);
+            let crc2 = compute_crc24q(&data, init & 0x00FF_FFFF);
             prop_assert_eq!(crc1, crc2,
                 "CRC with init 0x{:08X} should equal CRC with masked init 0x{:06X}",
-                init, init & 0xFFFFFF);
+                init, init & 0x00FF_FFFF);
         }
 
         /// Property: Single bit errors are detected (CRC changes).
diff --git a/swiftnav/src/reference_frame/mod.rs b/swiftnav/src/reference_frame/mod.rs
index 9b2e95f..208e11a 100644
--- a/swiftnav/src/reference_frame/mod.rs
+++ b/swiftnav/src/reference_frame/mod.rs
@@ -579,6 +579,7 @@ mod tests {
     use params::TRANSFORMATIONS;
     use std::str::FromStr;
 
+    #[expect(clippy::too_many_lines)]
     #[test]
     fn reference_frame_strings() {
         assert_eq!(ReferenceFrame::ITRF88.to_string(), "ITRF88");
@@ -996,7 +997,7 @@ mod tests {
             },
         };
 
-        let params = transformation.params.clone();
+        let params = transformation.params;
         repo.add_transformation(transformation);
         assert_eq!(repo.count(), 2);
 
diff --git a/swiftnav/src/signal/code.rs b/swiftnav/src/signal/code.rs
index 9b461d4..2d90814 100644
--- a/swiftnav/src/signal/code.rs
+++ b/swiftnav/src/signal/code.rs
@@ -455,6 +455,7 @@ mod tests {
         assert!(Code::AuxBds.is_bds());
     }
 
+    #[expect(clippy::too_many_lines)]
     #[test]
     fn code_strings() {
         use std::str::FromStr;
diff --git a/swiftnav/src/signal/mod.rs b/swiftnav/src/signal/mod.rs
index 83c324d..e1a3c0d 100644
--- a/swiftnav/src/signal/mod.rs
+++ b/swiftnav/src/signal/mod.rs
@@ -133,6 +133,7 @@ impl fmt::Display for GnssSignal {
 mod tests {
     use super::*;
 
+    #[expect(clippy::too_many_lines)]
     #[test]
     fn signal_to_constellation() {
         assert_eq!(
diff --git a/swiftnav/src/time/gnss.rs b/swiftnav/src/time/gnss.rs
index 7bb6aad..4b9b9eb 100644
--- a/swiftnav/src/time/gnss.rs
+++ b/swiftnav/src/time/gnss.rs
@@ -742,7 +742,7 @@ mod tests {
     fn add_duration() {
         let mut t = GpsTime::new(0, 0.0).unwrap();
         let t_expected = GpsTime::new(0, 1.001).unwrap();
-        let d = Duration::new(1, 1000000);
+        let d = Duration::new(1, 1_000_000);
 
         t.add_duration(&d);
         assert_eq!(t, t_expected);
@@ -760,7 +760,7 @@ mod tests {
     fn subtract_duration() {
         let mut t = GpsTime::new(0, 1.001).unwrap();
         let t_expected = GpsTime::new(0, 0.0).unwrap();
-        let d = Duration::new(1, 1000000);
+        let d = Duration::new(1, 1_000_000);
 
         t.subtract_duration(&d);
         assert_eq!(t, t_expected);
@@ -783,14 +783,14 @@ mod tests {
         let epsilon = 1e-5;
 
         let test_cases = [
-            GpsTime::new_unchecked(1234, 567890.01),
-            GpsTime::new_unchecked(1234, 567890.0501),
-            GpsTime::new_unchecked(1234, 604800.06),
+            GpsTime::new_unchecked(1234, 567_890.01),
+            GpsTime::new_unchecked(1234, 567_890.050_1),
+            GpsTime::new_unchecked(1234, 604_800.06),
         ];
 
         let expectations = [
-            GpsTime::new_unchecked(1234, 567890.00),
-            GpsTime::new_unchecked(1234, 567890.10),
+            GpsTime::new_unchecked(1234, 567_890.00),
+            GpsTime::new_unchecked(1234, 567_890.10),
             GpsTime::new_unchecked(1235, 0.1),
         ];
 
@@ -812,14 +812,14 @@ mod tests {
         let epsilon = 1e-6;
 
         let test_cases = [
-            GpsTime::new_unchecked(1234, 567890.01),
-            GpsTime::new_unchecked(1234, 567890.0501),
-            GpsTime::new_unchecked(1234, 604800.06),
+            GpsTime::new_unchecked(1234, 567_890.01),
+            GpsTime::new_unchecked(1234, 567_890.050_1),
+            GpsTime::new_unchecked(1234, 604_800.06),
         ];
 
         let expectations = [
-            GpsTime::new_unchecked(1234, 567890.00),
-            GpsTime::new_unchecked(1234, 567890.00),
+            GpsTime::new_unchecked(1234, 567_890.00),
+            GpsTime::new_unchecked(1234, 567_890.00),
             GpsTime::new_unchecked(1235, 0.0),
         ];
 
@@ -840,7 +840,7 @@ mod tests {
 
         assert!(GalTime::new(-1, 0.0).is_err());
         assert!(GalTime::new(0, -1.0).is_err());
-        assert!(GalTime::new(0, consts::WEEK_SECS as f64 + 1.0).is_err());
+        assert!(GalTime::new(0, f64::from(consts::WEEK_SECS) + 1.0).is_err());
     }
 
     #[test]
@@ -854,6 +854,6 @@ mod tests {
 
         assert!(BdsTime::new(-1, 0.0).is_err());
         assert!(BdsTime::new(0, -1.0).is_err());
-        assert!(BdsTime::new(0, consts::WEEK_SECS as f64 + 1.0).is_err());
+        assert!(BdsTime::new(0, f64::from(consts::WEEK_SECS) + 1.0).is_err());
     }
 }
diff --git a/swiftnav/src/time/mod.rs b/swiftnav/src/time/mod.rs
index f6db360..0dc0788 100644
--- a/swiftnav/src/time/mod.rs
+++ b/swiftnav/src/time/mod.rs
@@ -98,13 +98,13 @@ mod tests {
     #[test]
     fn conversions() {
         const TEST_CASES: [GpsTime; 10] = [
-            GpsTime::new_unchecked(1234, 567890.0),
-            GpsTime::new_unchecked(1234, 567890.5),
-            GpsTime::new_unchecked(1234, 567890.0),
+            GpsTime::new_unchecked(1234, 567_890.0),
+            GpsTime::new_unchecked(1234, 567_890.5),
+            GpsTime::new_unchecked(1234, 567_890.0),
             GpsTime::new_unchecked(1234, 0.0),
-            GpsTime::new_unchecked(1000, 604578.0),
+            GpsTime::new_unchecked(1000, 604_578.0),
             GpsTime::new_unchecked(1001, 222.222),
-            GpsTime::new_unchecked(1001, 604578.0),
+            GpsTime::new_unchecked(1001, 604_578.0),
             GpsTime::new_unchecked(1939, 222.222),
             GpsTime::new_unchecked(1930, 16.0),
             GpsTime::new_unchecked(1930, 18.0), /* around Jan 2017 leap second */
diff --git a/swiftnav/src/time/utc.rs b/swiftnav/src/time/utc.rs
index 6336a97..3547a3c 100644
--- a/swiftnav/src/time/utc.rs
+++ b/swiftnav/src/time/utc.rs
@@ -485,32 +485,32 @@ mod tests {
         let test_cases: &[UtcOffsetTestdata] = &[
             /* July 1 1981 */
             UtcOffsetTestdata {
-                t: GpsTime::new_unchecked(77, 259199.0),
+                t: GpsTime::new_unchecked(77, 259_199.0),
                 d_utc: 0.0,
                 is_lse: false,
             },
             UtcOffsetTestdata {
-                t: GpsTime::new_unchecked(77, 259199.5),
+                t: GpsTime::new_unchecked(77, 259_199.5),
                 d_utc: 0.0,
                 is_lse: false,
             },
             UtcOffsetTestdata {
-                t: GpsTime::new_unchecked(77, 259200.0),
+                t: GpsTime::new_unchecked(77, 259_200.0),
                 d_utc: 0.0,
                 is_lse: true,
             },
             UtcOffsetTestdata {
-                t: GpsTime::new_unchecked(77, 259200.5),
+                t: GpsTime::new_unchecked(77, 259_200.5),
                 d_utc: 0.0,
                 is_lse: true,
             },
             UtcOffsetTestdata {
-                t: GpsTime::new_unchecked(77, 259201.0),
+                t: GpsTime::new_unchecked(77, 259_201.0),
                 d_utc: 1.0,
                 is_lse: false,
             },
             UtcOffsetTestdata {
-                t: GpsTime::new_unchecked(77, 259202.0),
+                t: GpsTime::new_unchecked(77, 259_202.0),
                 d_utc: 1.0,
                 is_lse: false,
             },
@@ -555,7 +555,10 @@ mod tests {
             let d_utc = test_case.t.gps_utc_offset_hardcoded();
             let is_lse = test_case.t.is_leap_second_event_hardcoded();
 
-            assert!(d_utc == test_case.d_utc && is_lse == test_case.is_lse, "test_case.t: {:?}, test_case.d_utc: {}, test_case.is_lse: {}, d_utc: {}, is_lse: {}", test_case.t, test_case.d_utc, test_case.is_lse, d_utc, is_lse);
+            #[expect(clippy::float_cmp)]
+            {
+                assert!(d_utc == test_case.d_utc && is_lse == test_case.is_lse, "test_case.t: {:?}, test_case.d_utc: {}, test_case.is_lse: {}, d_utc: {}, is_lse: {}", test_case.t, test_case.d_utc, test_case.is_lse, d_utc, is_lse);
+            }
         }
     }
 
@@ -567,7 +570,7 @@ mod tests {
             0.0,
             0.0,
             &GpsTime::new_unchecked(2080, 0.0),
-            &GpsTime::new_unchecked(2086, 259218.0 - 0.125),
+            &GpsTime::new_unchecked(2086, 259_218.0 - 0.125),
             18,
             19,
         )
@@ -579,7 +582,7 @@ mod tests {
             0.0,
             0.0,
             &GpsTime::new_unchecked(2080, 0.0),
-            &GpsTime::new_unchecked(2086, 259218.125),
+            &GpsTime::new_unchecked(2086, 259_218.125),
             18,
             19,
         )
@@ -593,7 +596,7 @@ mod tests {
             &GpsTime::new_unchecked(2080, 0.0),
             &GpsTime::new_unchecked(
                 2086,
-                259218.0 + 1e-12 * (6.0 * consts::WEEK_SECS as f64 + 259218.0),
+                259_218.0 + 1e-12 * (6.0 * f64::from(consts::WEEK_SECS) + 259_218.00),
             ),
             18,
             19,
@@ -608,13 +611,14 @@ mod tests {
             &GpsTime::new_unchecked(2080, 0.0),
             &GpsTime::new_unchecked(
                 2086,
-                259218.0 - 1e-12 * (6.0 * consts::WEEK_SECS as f64 + 259218.0),
+                259_218.0 - 1e-12 * (6.0 * f64::from(consts::WEEK_SECS) + 259_218.0),
             ),
             18,
             19,
         )
     }
 
+    #[expect(clippy::too_many_lines)]
     #[test]
     fn utc_params() {
         struct TestCase {
@@ -627,148 +631,148 @@ mod tests {
         let test_cases = [
             /* Jan 1 2020 (constant negative UTC offset) */
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.0 - 0.125),
+                t: GpsTime::new_unchecked(2086, 259_217.0 - 0.125),
                 d_utc: 18.0 - 0.125,
                 is_lse: false,
                 params: Some(make_p_neg_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.5 - 0.125),
+                t: GpsTime::new_unchecked(2086, 259_217.5 - 0.125),
                 d_utc: 18.0 - 0.125,
                 is_lse: false,
                 params: Some(make_p_neg_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.0 - 0.125),
+                t: GpsTime::new_unchecked(2086, 259_218.0 - 0.125),
                 d_utc: 18.0 - 0.125,
                 is_lse: true,
                 params: Some(make_p_neg_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.5 - 0.125),
+                t: GpsTime::new_unchecked(2086, 259_218.5 - 0.125),
                 d_utc: 18.0 - 0.125,
                 is_lse: true,
                 params: Some(make_p_neg_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.0 - 0.125),
+                t: GpsTime::new_unchecked(2086, 259_219.0 - 0.125),
                 d_utc: 19.0 - 0.125,
                 is_lse: false,
                 params: Some(make_p_neg_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.5 - 0.125),
+                t: GpsTime::new_unchecked(2086, 259_219.5 - 0.125),
                 d_utc: 19.0 - 0.125,
                 is_lse: false,
                 params: Some(make_p_neg_offset()),
             },
             /* Jan 1 2020 (constant positive UTC offset) */
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.125),
+                t: GpsTime::new_unchecked(2086, 259_217.125),
                 d_utc: 18.125,
                 is_lse: false,
                 params: Some(make_p_pos_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.5 + 0.125),
+                t: GpsTime::new_unchecked(2086, 259_217.5 + 0.125),
                 d_utc: 18.125,
                 is_lse: false,
                 params: Some(make_p_pos_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.125),
+                t: GpsTime::new_unchecked(2086, 259_218.125),
                 d_utc: 18.125,
                 is_lse: true,
                 params: Some(make_p_pos_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.5 + 0.125),
+                t: GpsTime::new_unchecked(2086, 259_218.5 + 0.125),
                 d_utc: 18.125,
                 is_lse: true,
                 params: Some(make_p_pos_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.125),
+                t: GpsTime::new_unchecked(2086, 259_219.125),
                 d_utc: 19.125,
                 is_lse: false,
                 params: Some(make_p_pos_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.5 + 0.125),
+                t: GpsTime::new_unchecked(2086, 259_219.5 + 0.125),
                 d_utc: 19.125,
                 is_lse: false,
                 params: Some(make_p_pos_offset()),
             },
             /* Jan 1 2020 (positive UTC linear correction) */
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.0),
+                t: GpsTime::new_unchecked(2086, 259_217.0),
                 d_utc: 18.0,
                 is_lse: false,
                 params: Some(make_p_pos_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.5),
+                t: GpsTime::new_unchecked(2086, 259_217.5),
                 d_utc: 18.0,
                 is_lse: false,
                 params: Some(make_p_pos_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.0001),
+                t: GpsTime::new_unchecked(2086, 259_218.000_1),
                 d_utc: 18.0,
                 is_lse: true,
                 params: Some(make_p_pos_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.5),
+                t: GpsTime::new_unchecked(2086, 259_218.5),
                 d_utc: 18.0,
                 is_lse: true,
                 params: Some(make_p_pos_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.0001),
+                t: GpsTime::new_unchecked(2086, 259_219.000_1),
                 d_utc: 19.0,
                 is_lse: false,
                 params: Some(make_p_pos_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.5),
+                t: GpsTime::new_unchecked(2086, 259_219.5),
                 d_utc: 19.0,
                 is_lse: false,
                 params: Some(make_p_pos_trend()),
             },
             /* Jan 1 2020 (negative UTC linear correction) */
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.0),
+                t: GpsTime::new_unchecked(2086, 259_217.0),
                 d_utc: 18.0,
                 is_lse: false,
                 params: Some(make_p_neg_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.5),
+                t: GpsTime::new_unchecked(2086, 259_217.5),
                 d_utc: 18.0,
                 is_lse: false,
                 params: Some(make_p_neg_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.0),
+                t: GpsTime::new_unchecked(2086, 259_218.0),
                 d_utc: 18.0,
                 is_lse: true,
                 params: Some(make_p_neg_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.5),
+                t: GpsTime::new_unchecked(2086, 259_218.5),
                 d_utc: 18.0,
                 is_lse: true,
                 params: Some(make_p_neg_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.0),
+                t: GpsTime::new_unchecked(2086, 259_219.0),
                 d_utc: 19.0,
                 is_lse: false,
                 params: Some(make_p_neg_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.5),
+                t: GpsTime::new_unchecked(2086, 259_219.5),
                 d_utc: 19.0,
                 is_lse: false,
                 params: Some(make_p_neg_trend()),
@@ -798,6 +802,7 @@ mod tests {
         }
     }
 
+    #[expect(clippy::too_many_lines)]
     #[test]
     fn gps2utc() {
         /* test leap second on 1st Jan 2020 */
@@ -841,27 +846,27 @@ mod tests {
         let test_cases = [
             /* July 1 1981 */
             TestCase {
-                t: GpsTime::new_unchecked(77, 259199.0),
+                t: GpsTime::new_unchecked(77, 259_199.0),
                 u: UtcExpectation::new(1981, 6, 30, 23, 59, 59.0),
                 p: None,
             },
             TestCase {
-                t: GpsTime::new_unchecked(77, 259199.5),
+                t: GpsTime::new_unchecked(77, 259_199.5),
                 u: UtcExpectation::new(1981, 6, 30, 23, 59, 59.5),
                 p: None,
             },
             TestCase {
-                t: GpsTime::new_unchecked(77, 259200.0),
+                t: GpsTime::new_unchecked(77, 259_200.0),
                 u: UtcExpectation::new(1981, 6, 30, 23, 59, 60.0),
                 p: None,
             },
             TestCase {
-                t: GpsTime::new_unchecked(77, 259200.5),
+                t: GpsTime::new_unchecked(77, 259_200.5),
                 u: UtcExpectation::new(1981, 6, 30, 23, 59, 60.5),
                 p: None,
             },
             TestCase {
-                t: GpsTime::new_unchecked(77, 259201.0),
+                t: GpsTime::new_unchecked(77, 259_201.0),
                 u: UtcExpectation::new(1981, 7, 1, 00, 00, 00.0),
                 p: None,
             },
@@ -920,108 +925,108 @@ mod tests {
             /* Jan 1 2020 (leap second announced in utc_params_t above, constant
             negative offset) */
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.0 - 0.125),
+                t: GpsTime::new_unchecked(2086, 259_217.0 - 0.125),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 59.0),
                 p: Some(make_p_neg_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.5 - 0.125),
+                t: GpsTime::new_unchecked(2086, 259_217.5 - 0.125),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 59.5),
                 p: Some(make_p_neg_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.0 - 0.125),
+                t: GpsTime::new_unchecked(2086, 259_218.0 - 0.125),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 60.0),
                 p: Some(make_p_neg_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.5 - 0.125),
+                t: GpsTime::new_unchecked(2086, 259_218.5 - 0.125),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 60.5),
                 p: Some(make_p_neg_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.0 - 0.125),
+                t: GpsTime::new_unchecked(2086, 259_219.0 - 0.125),
                 u: UtcExpectation::new(2020, 1, 1, 00, 00, 00.0),
                 p: Some(make_p_neg_offset()),
             },
             /* Jan 1 2020 (leap second announced in utc_params_t above, constant
             positive offset) */
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.125),
+                t: GpsTime::new_unchecked(2086, 259_217.125),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 59.0),
                 p: Some(make_p_pos_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.5 + 0.125),
+                t: GpsTime::new_unchecked(2086, 259_217.5 + 0.125),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 59.5),
                 p: Some(make_p_pos_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.125),
+                t: GpsTime::new_unchecked(2086, 259_218.125),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 60.0),
                 p: Some(make_p_pos_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.5 + 0.125),
+                t: GpsTime::new_unchecked(2086, 259_218.5 + 0.125),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 60.5),
                 p: Some(make_p_pos_offset()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.125),
+                t: GpsTime::new_unchecked(2086, 259_219.125),
                 u: UtcExpectation::new(2020, 1, 1, 00, 00, 00.0),
                 p: Some(make_p_pos_offset()),
             },
             /* Jan 1 2020 (leap second announced in utc_params_t above, positive UTC
             linear correction) */
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.0),
+                t: GpsTime::new_unchecked(2086, 259_217.0),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 59.0),
                 p: Some(make_p_pos_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.5),
+                t: GpsTime::new_unchecked(2086, 259_217.5),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 59.5),
                 p: Some(make_p_pos_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.0),
+                t: GpsTime::new_unchecked(2086, 259_218.0),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 60.0),
                 p: Some(make_p_pos_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.5),
+                t: GpsTime::new_unchecked(2086, 259_218.5),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 60.5),
                 p: Some(make_p_pos_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.00001),
+                t: GpsTime::new_unchecked(2086, 259_219.000_01),
                 u: UtcExpectation::new(2020, 1, 1, 00, 00, 00.0),
                 p: Some(make_p_pos_trend()),
             },
             /* Jan 1 2020 (leap second announced in utc_params_t above, negative UTC
             linear correction) */
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.0),
+                t: GpsTime::new_unchecked(2086, 259_217.0),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 59.0),
                 p: Some(make_p_neg_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259217.5),
+                t: GpsTime::new_unchecked(2086, 259_217.5),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 59.5),
                 p: Some(make_p_neg_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.0),
+                t: GpsTime::new_unchecked(2086, 259_218.0),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 60.0),
                 p: Some(make_p_neg_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259218.5),
+                t: GpsTime::new_unchecked(2086, 259_218.5),
                 u: UtcExpectation::new(2019, 12, 31, 23, 59, 60.5),
                 p: Some(make_p_neg_trend()),
             },
             TestCase {
-                t: GpsTime::new_unchecked(2086, 259219.0),
+                t: GpsTime::new_unchecked(2086, 259_219.0),
                 u: UtcExpectation::new(2020, 1, 1, 00, 00, 00.0),
                 p: Some(make_p_neg_trend()),
             },
@@ -1099,13 +1104,13 @@ mod tests {
             Utc,
         );
 
-        let converted: DateTime<Utc> = swift_date.clone().into();
+        let converted: DateTime<Utc> = swift_date.into();
         assert!((converted - expected_utc).to_std().unwrap() < epsilon);
-        assert_eq!(converted.year(), swift_date.year() as i32);
-        assert_eq!(converted.month(), swift_date.month() as u32);
-        assert_eq!(converted.day(), swift_date.day_of_month() as u32);
-        assert_eq!(converted.hour(), swift_date.hour() as u32);
-        assert_eq!(converted.minute(), swift_date.minute() as u32);
+        assert_eq!(converted.year(), i32::from(swift_date.year()));
+        assert_eq!(converted.month(), u32::from(swift_date.month()));
+        assert_eq!(converted.day(), u32::from(swift_date.day_of_month()));
+        assert_eq!(converted.hour(), u32::from(swift_date.hour()));
+        assert_eq!(converted.minute(), u32::from(swift_date.minute()));
         assert_eq!(converted.second(), swift_date.seconds() as u32);
     }
 }
diff --git a/swiftnav/tests/reference_frames.rs b/swiftnav/tests/reference_frames.rs
index 0bcbf3d..ace7d8a 100644
--- a/swiftnav/tests/reference_frames.rs
+++ b/swiftnav/tests/reference_frames.rs
@@ -889,7 +889,7 @@ fn dref91_r2016() {
         ReferenceFrame::ITRF2020,
         ECEF::new(3842152.805, 563402.164, 5042888.600),
         None,
-        UtcTime::from_parts(2023, 02, 22, 0, 0, 0.).to_gps_hardcoded(),
+        UtcTime::from_parts(2023, 2, 22, 0, 0, 0.).to_gps_hardcoded(),
     );
     let transformations = TransformationRepository::from_builtin();
 

From df779c0814798e850719d8fb78332aa4fd210b54 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Fri, 24 Oct 2025 17:19:42 -0700
Subject: [PATCH 02/17] add a few nmea types

---
 swiftnav/Cargo.toml        | 16 ++++++++--------
 swiftnav/src/coords/llh.rs | 22 ++++++++++++++++++++++
 swiftnav/src/coords/mod.rs |  2 ++
 swiftnav/src/lib.rs        |  1 +
 4 files changed, 33 insertions(+), 8 deletions(-)

diff --git a/swiftnav/Cargo.toml b/swiftnav/Cargo.toml
index 5d27706..921349e 100644
--- a/swiftnav/Cargo.toml
+++ b/swiftnav/Cargo.toml
@@ -10,18 +10,18 @@ license = "LGPL-3.0"
 rust-version = "1.85.0"
 
 [dependencies]
-rustversion = "1.0"
-chrono = { version = "0.4", optional = true }
-strum = { version = "0.27", features = ["derive"] }
-nalgebra = "0.33"
-thiserror = "2.0"
+bon = "3.8.1"
+rustversion = "1.0.22"
+chrono = { version = "0.4.42", optional = true }
+strum = { version = "0.27.2", features = ["derive"] }
+nalgebra = "0.34.1"
+thiserror = "2.0.17"
 
 [dev-dependencies]
 float_eq = "1.0.1"
-proptest = "1.5"
+proptest = "1.8.0"
 
 # This tells docs.rs to include the katex header for math formatting
 # To do this locally 
 [package.metadata.docs.rs]
-rustdoc-args = [ "--html-in-header", "katex-header.html" ]
-
+rustdoc-args = ["--html-in-header", "katex-header.html"]
diff --git a/swiftnav/src/coords/llh.rs b/swiftnav/src/coords/llh.rs
index 174fbb2..58b03b3 100644
--- a/swiftnav/src/coords/llh.rs
+++ b/swiftnav/src/coords/llh.rs
@@ -1,3 +1,5 @@
+use crate::coords::{LatitudinalHemisphere, LongitudinalHemisphere};
+
 use super::{Ellipsoid, ECEF, WGS84};
 use nalgebra::Vector3;
 
@@ -44,12 +46,32 @@ impl LLHDegrees {
         self.0.x
     }
 
+    /// Get the latitudinal hemisphere
+    #[must_use]
+    pub fn latitudinal_hemisphere(&self) -> LatitudinalHemisphere {
+        if self.latitude() >= 0.0 {
+            LatitudinalHemisphere::North
+        } else {
+            LatitudinalHemisphere::South
+        }
+    }
+
     /// Get the longitude component
     #[must_use]
     pub fn longitude(&self) -> f64 {
         self.0.y
     }
 
+    /// Get the longitudinal hemisphere
+    #[must_use]
+    pub fn longitudinal_hemisphere(&self) -> LongitudinalHemisphere {
+        if self.longitude() >= 0.0 {
+            LongitudinalHemisphere::East
+        } else {
+            LongitudinalHemisphere::West
+        }
+    }
+
     /// Get the height component
     #[must_use]
     pub fn height(&self) -> f64 {
diff --git a/swiftnav/src/coords/mod.rs b/swiftnav/src/coords/mod.rs
index 198f035..fb3d202 100644
--- a/swiftnav/src/coords/mod.rs
+++ b/swiftnav/src/coords/mod.rs
@@ -76,11 +76,13 @@
 
 mod ecef;
 mod ellipsoid;
+mod hemisphere;
 mod llh;
 mod ned;
 
 pub use ecef::*;
 pub use ellipsoid::*;
+pub use hemisphere::*;
 pub use llh::*;
 pub use ned::*;
 
diff --git a/swiftnav/src/lib.rs b/swiftnav/src/lib.rs
index 2dd39f4..5ae6d3d 100644
--- a/swiftnav/src/lib.rs
+++ b/swiftnav/src/lib.rs
@@ -58,6 +58,7 @@
 pub mod coords;
 pub mod edc;
 mod math;
+pub mod nmea;
 pub mod reference_frame;
 pub mod signal;
 pub mod time;

From 83ba99057eaf96b0cbc4560fc4587bd7b663d36a Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Fri, 24 Oct 2025 17:20:48 -0700
Subject: [PATCH 03/17] clean up test

---
 swiftnav/src/coords/hemisphere.rs |  43 +++++++
 swiftnav/src/nmea/gga.rs          | 191 ++++++++++++++++++++++++++++++
 swiftnav/src/nmea/mod.rs          |   5 +
 swiftnav/src/nmea/source.rs       |  16 +++
 4 files changed, 255 insertions(+)
 create mode 100644 swiftnav/src/coords/hemisphere.rs
 create mode 100644 swiftnav/src/nmea/gga.rs
 create mode 100644 swiftnav/src/nmea/mod.rs
 create mode 100644 swiftnav/src/nmea/source.rs

diff --git a/swiftnav/src/coords/hemisphere.rs b/swiftnav/src/coords/hemisphere.rs
new file mode 100644
index 0000000..fd49bd3
--- /dev/null
+++ b/swiftnav/src/coords/hemisphere.rs
@@ -0,0 +1,43 @@
+use core::fmt;
+
+pub enum LatitudinalHemisphere {
+    North,
+    South,
+}
+
+impl fmt::Display for LatitudinalHemisphere {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            LatitudinalHemisphere::North => write!(f, "N"),
+            LatitudinalHemisphere::South => write!(f, "S"),
+        }
+    }
+}
+
+pub enum LongitudinalHemisphere {
+    East,
+    West,
+}
+
+impl fmt::Display for LongitudinalHemisphere {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            LongitudinalHemisphere::East => write!(f, "E"),
+            LongitudinalHemisphere::West => write!(f, "W"),
+        }
+    }
+}
+
+pub enum Hemisphere {
+    Latitudinal(LatitudinalHemisphere),
+    Longitudinal(LongitudinalHemisphere),
+}
+
+impl fmt::Display for Hemisphere {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Hemisphere::Latitudinal(hemisphere) => write!(f, "{hemisphere}"),
+            Hemisphere::Longitudinal(hemisphere) => write!(f, "{hemisphere}"),
+        }
+    }
+}
diff --git a/swiftnav/src/nmea/gga.rs b/swiftnav/src/nmea/gga.rs
new file mode 100644
index 0000000..2983c22
--- /dev/null
+++ b/swiftnav/src/nmea/gga.rs
@@ -0,0 +1,191 @@
+use std::{
+    fmt::{self},
+    time::Duration,
+};
+
+use bon::Builder;
+use chrono::{DateTime, Timelike, Utc};
+
+use crate::{coords::LLHDegrees, nmea::Source};
+
+/// Quality of GPS solution
+#[derive(Debug, PartialEq, Clone, Copy)]
+pub enum GPSQuality {
+    /// Fix not available or invalid
+    NoFix,
+    /// GPS SPS Mode, fix valid
+    GPS,
+    /// Differential GPS, SPS Mode, fix valid
+    DGPS,
+    /// GPS PPS (pulse per second), fix valid
+    PPS,
+    /// RTK (real time kinematic). System used in RTK mode with fixed integers
+    RTK,
+    /// Float RTK, satelite system used in RTK mode, floating integers
+    FRTK,
+    /// Estimated (dead reckoning) mode.
+    Estimated,
+    /// Manual input mode
+    Manual,
+    /// Simulated mode
+    Simulated,
+}
+
+impl fmt::Display for GPSQuality {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            GPSQuality::NoFix => write!(f, "0"),
+            GPSQuality::GPS => write!(f, "1"),
+            GPSQuality::DGPS => write!(f, "2"),
+            GPSQuality::PPS => write!(f, "3"),
+            GPSQuality::RTK => write!(f, "4"),
+            GPSQuality::FRTK => write!(f, "5"),
+            GPSQuality::Estimated => write!(f, "6"),
+            GPSQuality::Manual => write!(f, "7"),
+            GPSQuality::Simulated => write!(f, "8"),
+        }
+    }
+}
+
+/// Geographic coordinates including altitude, GPS solution quality, DGPS usage information.
+#[derive(Debug, PartialEq, Clone, Builder)]
+pub struct GGA {
+    /// Navigational system.
+    #[builder(default = Source::GPS)]
+    pub source: Source,
+    /// Time of fix in UTC.
+    #[builder(default = Utc::now())]
+    pub time: DateTime<Utc>,
+    /// Latitude, longitude and height in degrees.
+    pub llh: LLHDegrees,
+    /// Quality of GPS solution.
+    #[builder(default = GPSQuality::GPS)]
+    pub gps_quality: GPSQuality,
+    /// Sattelites in use
+    pub sat_in_use: u8,
+    /// Horizontal dilusion of presicion
+    pub hdop: f32,
+    /// The difference between reference ellipsoid surface and mean-sea-level.
+    pub geoidal_separation: Option<f32>,
+    /// DGPS data age. None if DGPS not in use.
+    pub age_dgps: Option<Duration>,
+    /// ID of reference DGPS station used for fix. None if DGPS not in use.
+    pub dgps_station_id: Option<u16>,
+}
+
+impl GGA {
+    // converts the GGA struct into an NMEA sentence
+    #[must_use]
+    pub fn to_sentence(&self) -> String {
+        // NOTE(ted): We are formatting here a bit strange because for some ungodly reason,
+        // chrono chose not to allow for abitrary fractional seconds precision when formatting
+        // Construct timestamp in HHMMSS.SS format
+        let hour = self.time.hour();
+        let minute = self.time.minute();
+        let second = f64::from(self.time.second());
+        let second_fracs = f64::from(self.time.nanosecond()) / 1_000_000_000.0;
+
+        let timestamp = format!("{hour}{minute}{:.2}", second + second_fracs);
+
+        let latitude = self.llh.latitude();
+        let latitudinal_hemisphere = self.llh.latitudinal_hemisphere();
+
+        let longitude = self.llh.longitude();
+        let longitudinal_hemisphere = self.llh.longitudinal_hemisphere();
+
+        let gps_quality = self.gps_quality;
+
+        let sat_in_use = self.sat_in_use;
+
+        let hdop = self.hdop;
+
+        // NOTE(ted): This is actually not the right value to use, however, we don't really use height for finding information like nearest station so it's ok to use for now
+        let height = "0.0";
+
+        // if DGPS is not used, this should be a null field
+        let age_dgps = if matches!(gps_quality, GPSQuality::DGPS) {
+            let age = self.age_dgps.map_or(0.0, |age| age.as_secs_f64());
+
+            format!("{age:.1}")
+        } else {
+            String::new()
+        };
+
+        let geoidal_separation = self
+            .geoidal_separation
+            .map_or(String::new(), |sep| format!("{sep:.2}"));
+
+        let dgps_station_id = self
+            .dgps_station_id
+            .map_or(String::new(), |id| id.to_string());
+
+        let sentence = format!(
+            "$GPGGA,{timestamp},{latitude:.6},{latitudinal_hemisphere},{longitude:.6},{longitudinal_hemisphere},{gps_quality},{sat_in_use},{hdop:.1},{height:.6},M,{geoidal_separation},{age_dgps:.1},{dgps_station_id}",
+        );
+
+        // NOTE(ted): We should skip the first character in the sentence (the '$')
+        // https://forum.arduino.cc/t/nmea-checksums-explained/1046083
+        let checksum = nmea_checksum(&sentence[1..]);
+
+        format!("{sentence}*{checksum}\r\n")
+    }
+}
+
+fn u8_to_nibbles(byte: u8) -> (u8, u8) {
+    // The high nibble is obtained by shifting the byte 4 bits to the right.
+    // This discards the lower 4 bits and moves the upper 4 bits into the lower 4 bit positions.
+    let high_nibble = byte >> 4;
+
+    // The low nibble is obtained by masking the byte with 0x0F (binary 0000_1111).
+    // This keeps only the lower 4 bits and sets the upper 4 bits to zero.
+    let low_nibble = byte & 0x0F;
+
+    (high_nibble, low_nibble)
+}
+
+/// Convert a nibble (4 bits) to its ASCII character representation
+fn u8_to_ascii_char(nibble: u8) -> char {
+    // if we are between 0 and 9, we map to '0' to '9'
+    if nibble <= 0x9 {
+        (nibble + b'0') as char
+    // else, we map to 'A' to 'F'
+    } else {
+        (nibble - 10 + b'A') as char
+    }
+}
+
+fn nmea_checksum(sentence: &str) -> String {
+    let mut checksum = 0;
+    for byte in sentence.bytes() {
+        checksum ^= byte;
+    }
+
+    let (nibble1, nibble2) = u8_to_nibbles(checksum);
+
+    let char1 = u8_to_ascii_char(nibble1);
+    let char2 = u8_to_ascii_char(nibble2);
+
+    format!("{char1}{char2}")
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn gga_can_be_turned_into_an_nmea_sentence() {
+        let gga = GGA::builder()
+            .sat_in_use(12)
+            .time(DateTime::from_timestamp(1_761_351_489, 0).unwrap())
+            .hdop(0.9)
+            .llh(super::LLHDegrees::new(37.7749, -122.4194, 10.0))
+            .build();
+
+        let sentence = gga.to_sentence();
+
+        assert_eq!(
+            sentence,
+            "$GPGGA,0189.00,37.774900,N,-122.419400,W,1,12,0.9,0.0,M,,,*26\r\n"
+        );
+    }
+}
diff --git a/swiftnav/src/nmea/mod.rs b/swiftnav/src/nmea/mod.rs
new file mode 100644
index 0000000..c0898f5
--- /dev/null
+++ b/swiftnav/src/nmea/mod.rs
@@ -0,0 +1,5 @@
+mod gga;
+mod source;
+
+pub use gga::*;
+pub use source::*;
diff --git a/swiftnav/src/nmea/source.rs b/swiftnav/src/nmea/source.rs
new file mode 100644
index 0000000..1462bad
--- /dev/null
+++ b/swiftnav/src/nmea/source.rs
@@ -0,0 +1,16 @@
+/// Source of NMEA sentence like GPS, GLONASS or other.
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub enum Source {
+    /// USA Global Positioning System
+    GPS = 0b1,
+    /// Russian Federation GLONASS
+    GLONASS = 0b10,
+    /// European Union Gallileo
+    Gallileo = 0b100,
+    /// China's Beidou
+    Beidou = 0b1000,
+    /// Global Navigation Sattelite System. Some combination of other systems. Depends on receiver model, receiver settings, etc..
+    GNSS = 0b10000,
+    /// `MediaTek` NMEA packet protocol
+    MTK = 0b10_0000,
+}

From ed88d7df02f1b2aefeee32e2acfb2b965e2237fe Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Fri, 24 Oct 2025 17:23:42 -0700
Subject: [PATCH 04/17] update rust dep

---
 .github/workflows/ci.yaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 371ddcb..cd18201 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -65,7 +65,7 @@ jobs:
           # MSRV
           - os: ubuntu-latest
             binary_target: x86_64-unknown-linux-gnu
-            toolchain: 1.85.0
+            toolchain: 1.90.0
     steps:
       - uses: actions/checkout@v5
         with:

From e1421123f15a32fbf757a756571b93db67f199a7 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 10:19:36 -0700
Subject: [PATCH 05/17] little refactor

---
 swiftnav/src/nmea/checksum.rs | 43 ++++++++++++++++++++++++++++++++
 swiftnav/src/nmea/gga.rs      | 46 ++++-------------------------------
 swiftnav/src/nmea/mod.rs      |  2 ++
 3 files changed, 50 insertions(+), 41 deletions(-)
 create mode 100644 swiftnav/src/nmea/checksum.rs

diff --git a/swiftnav/src/nmea/checksum.rs b/swiftnav/src/nmea/checksum.rs
new file mode 100644
index 0000000..b0a21b5
--- /dev/null
+++ b/swiftnav/src/nmea/checksum.rs
@@ -0,0 +1,43 @@
+fn u8_to_nibbles(byte: u8) -> (u8, u8) {
+    // The high nibble is obtained by shifting the byte 4 bits to the right.
+    // This discards the lower 4 bits and moves the upper 4 bits into the lower 4 bit positions.
+    let high_nibble = byte >> 4;
+
+    // The low nibble is obtained by masking the byte with 0x0F (binary 0000_1111).
+    // This keeps only the lower 4 bits and sets the upper 4 bits to zero.
+    let low_nibble = byte & 0x0F;
+
+    (high_nibble, low_nibble)
+}
+
+/// Convert a nibble (4 bits) to its ASCII character representation
+fn u8_to_ascii_char(nibble: u8) -> char {
+    if nibble <= 0x9 {
+        (nibble + b'0') as char
+    } else {
+        (nibble - 10 + b'A') as char
+    }
+}
+
+// Calculate the NMEA checksum for a given sentence
+// https://forum.arduino.cc/t/nmea-checksums-explained/1046083
+#[must_use]
+pub fn calculate_checksum(sentence: &str) -> String {
+    let mut checksum = 0;
+
+    for (i, byte) in sentence.bytes().enumerate() {
+        // Skip the starting '$' and the '*' before the checksum
+        if (i == 0 && byte == b'$') || byte == b'*' {
+            continue;
+        }
+
+        checksum ^= byte;
+    }
+
+    let (nibble1, nibble2) = u8_to_nibbles(checksum);
+
+    let char1 = u8_to_ascii_char(nibble1);
+    let char2 = u8_to_ascii_char(nibble2);
+
+    format!("{char1}{char2}")
+}
diff --git a/swiftnav/src/nmea/gga.rs b/swiftnav/src/nmea/gga.rs
index 2983c22..133f160 100644
--- a/swiftnav/src/nmea/gga.rs
+++ b/swiftnav/src/nmea/gga.rs
@@ -6,7 +6,10 @@ use std::{
 use bon::Builder;
 use chrono::{DateTime, Timelike, Utc};
 
-use crate::{coords::LLHDegrees, nmea::Source};
+use crate::{
+    coords::LLHDegrees,
+    nmea::{self, Source},
+};
 
 /// Quality of GPS solution
 #[derive(Debug, PartialEq, Clone, Copy)]
@@ -123,51 +126,12 @@ impl GGA {
             "$GPGGA,{timestamp},{latitude:.6},{latitudinal_hemisphere},{longitude:.6},{longitudinal_hemisphere},{gps_quality},{sat_in_use},{hdop:.1},{height:.6},M,{geoidal_separation},{age_dgps:.1},{dgps_station_id}",
         );
 
-        // NOTE(ted): We should skip the first character in the sentence (the '$')
-        // https://forum.arduino.cc/t/nmea-checksums-explained/1046083
-        let checksum = nmea_checksum(&sentence[1..]);
+        let checksum = nmea::calculate_checksum(&sentence);
 
         format!("{sentence}*{checksum}\r\n")
     }
 }
 
-fn u8_to_nibbles(byte: u8) -> (u8, u8) {
-    // The high nibble is obtained by shifting the byte 4 bits to the right.
-    // This discards the lower 4 bits and moves the upper 4 bits into the lower 4 bit positions.
-    let high_nibble = byte >> 4;
-
-    // The low nibble is obtained by masking the byte with 0x0F (binary 0000_1111).
-    // This keeps only the lower 4 bits and sets the upper 4 bits to zero.
-    let low_nibble = byte & 0x0F;
-
-    (high_nibble, low_nibble)
-}
-
-/// Convert a nibble (4 bits) to its ASCII character representation
-fn u8_to_ascii_char(nibble: u8) -> char {
-    // if we are between 0 and 9, we map to '0' to '9'
-    if nibble <= 0x9 {
-        (nibble + b'0') as char
-    // else, we map to 'A' to 'F'
-    } else {
-        (nibble - 10 + b'A') as char
-    }
-}
-
-fn nmea_checksum(sentence: &str) -> String {
-    let mut checksum = 0;
-    for byte in sentence.bytes() {
-        checksum ^= byte;
-    }
-
-    let (nibble1, nibble2) = u8_to_nibbles(checksum);
-
-    let char1 = u8_to_ascii_char(nibble1);
-    let char2 = u8_to_ascii_char(nibble2);
-
-    format!("{char1}{char2}")
-}
-
 #[cfg(test)]
 mod test {
     use super::*;
diff --git a/swiftnav/src/nmea/mod.rs b/swiftnav/src/nmea/mod.rs
index c0898f5..8cdfef7 100644
--- a/swiftnav/src/nmea/mod.rs
+++ b/swiftnav/src/nmea/mod.rs
@@ -1,5 +1,7 @@
+mod checksum;
 mod gga;
 mod source;
 
+pub use checksum::*;
 pub use gga::*;
 pub use source::*;

From 46ff14b106b15f664efcf9d3a920d9e62c3a00ff Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 10:42:50 -0700
Subject: [PATCH 06/17] add more tests

---
 swiftnav/src/nmea/checksum.rs | 49 ++++++++++++++++++++++++++++++++-
 swiftnav/src/nmea/gga.rs      | 51 ++++++++++++++++++++++++++++++++---
 2 files changed, 96 insertions(+), 4 deletions(-)

diff --git a/swiftnav/src/nmea/checksum.rs b/swiftnav/src/nmea/checksum.rs
index b0a21b5..ee3d00e 100644
--- a/swiftnav/src/nmea/checksum.rs
+++ b/swiftnav/src/nmea/checksum.rs
@@ -25,9 +25,16 @@ fn u8_to_ascii_char(nibble: u8) -> char {
 pub fn calculate_checksum(sentence: &str) -> String {
     let mut checksum = 0;
 
+    let mut at_checksum_validation_value = false;
+
     for (i, byte) in sentence.bytes().enumerate() {
         // Skip the starting '$' and the '*' before the checksum
-        if (i == 0 && byte == b'$') || byte == b'*' {
+        if (i == 0 && byte == b'$') || at_checksum_validation_value {
+            continue;
+        }
+
+        if byte == b'*' {
+            at_checksum_validation_value = true;
             continue;
         }
 
@@ -41,3 +48,43 @@ pub fn calculate_checksum(sentence: &str) -> String {
 
     format!("{char1}{char2}")
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn test_calculate_checksum() {
+        let sentence = "GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,";
+        let checksum = super::calculate_checksum(sentence);
+        assert_eq!(checksum, "47");
+    }
+
+    #[test]
+    fn calculate_checksum_ignores_dollar_and_asterisk_tails() {
+        // NOTE(ted): All of these examples should produce the same checksum
+
+        // check with '$'
+        let sentence = "$GPGGA,0189.00,34.052200,N,-118.243700,W,2,8,1.2,0.0,M,1.00,2,42";
+        let checksum = super::calculate_checksum(sentence);
+        assert_eq!(checksum, "37");
+
+        //check with '$' and '*'
+        let sentence = "$GPGGA,0189.00,34.052200,N,-118.243700,W,2,8,1.2,0.0,M,1.00,2,42*";
+        let checksum = super::calculate_checksum(sentence);
+        assert_eq!(checksum, "37");
+
+        //check with '$' and '*' and fake checksum
+        let sentence = "$GPGGA,0189.00,34.052200,N,-118.243700,W,2,8,1.2,0.0,M,1.00,2,42*00";
+        let checksum = super::calculate_checksum(sentence);
+        assert_eq!(checksum, "37");
+
+        //check '*'
+        let sentence = "GPGGA,0189.00,34.052200,N,-118.243700,W,2,8,1.2,0.0,M,1.00,2,42*";
+        let checksum = super::calculate_checksum(sentence);
+        assert_eq!(checksum, "37");
+
+        //check '*' and fake checksum
+        let sentence = "GPGGA,0189.00,34.052200,N,-118.243700,W,2,8,1.2,0.0,M,1.00,2,42*00";
+        let checksum = super::calculate_checksum(sentence);
+        assert_eq!(checksum, "37");
+    }
+}
diff --git a/swiftnav/src/nmea/gga.rs b/swiftnav/src/nmea/gga.rs
index 133f160..bebaea6 100644
--- a/swiftnav/src/nmea/gga.rs
+++ b/swiftnav/src/nmea/gga.rs
@@ -118,9 +118,12 @@ impl GGA {
             .geoidal_separation
             .map_or(String::new(), |sep| format!("{sep:.2}"));
 
-        let dgps_station_id = self
-            .dgps_station_id
-            .map_or(String::new(), |id| id.to_string());
+        let dgps_station_id = if matches!(gps_quality, GPSQuality::DGPS) {
+            self.dgps_station_id
+                .map_or(String::new(), |id| id.to_string())
+        } else {
+            String::new()
+        };
 
         let sentence = format!(
             "$GPGGA,{timestamp},{latitude:.6},{latitudinal_hemisphere},{longitude:.6},{longitudinal_hemisphere},{gps_quality},{sat_in_use},{hdop:.1},{height:.6},M,{geoidal_separation},{age_dgps:.1},{dgps_station_id}",
@@ -152,4 +155,46 @@ mod test {
             "$GPGGA,0189.00,37.774900,N,-122.419400,W,1,12,0.9,0.0,M,,,*26\r\n"
         );
     }
+
+    #[test]
+    fn gga_with_dgps_can_be_turned_into_an_nmea_sentence() {
+        let gga = GGA::builder()
+            .sat_in_use(8)
+            .time(DateTime::from_timestamp(1_761_351_489, 0).unwrap())
+            .hdop(1.2)
+            .llh(super::LLHDegrees::new(34.0522, -118.2437, 15.0))
+            .gps_quality(GPSQuality::DGPS)
+            .age_dgps(Duration::from_secs_f64(2.5))
+            .geoidal_separation(1.0)
+            .dgps_station_id(42)
+            .build();
+
+        let sentence = gga.to_sentence();
+
+        assert_eq!(
+            sentence,
+            "$GPGGA,0189.00,34.052200,N,-118.243700,W,2,8,1.2,0.0,M,1.00,2,42*37\r\n"
+        );
+    }
+
+    #[test]
+    fn gga_with_dgps_fields_that_is_not_dgps_is_ignored() {
+        let gga = GGA::builder()
+            .sat_in_use(8)
+            .time(DateTime::from_timestamp(1_761_351_489, 0).unwrap())
+            .hdop(1.2)
+            .llh(super::LLHDegrees::new(34.0522, -118.2437, 15.0))
+            .gps_quality(GPSQuality::GPS)
+            .age_dgps(Duration::from_secs_f64(2.5))
+            .geoidal_separation(1.0)
+            .dgps_station_id(42)
+            .build();
+
+        let sentence = gga.to_sentence();
+
+        assert_eq!(
+            sentence,
+            "$GPGGA,0189.00,34.052200,N,-118.243700,W,1,8,1.2,0.0,M,1.00,,*00\r\n"
+        );
+    }
 }

From 9be6411ef4e389a6d9a80b365e151b69ceec73e3 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 10:49:39 -0700
Subject: [PATCH 07/17] add comment

---
 swiftnav/src/nmea/checksum.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/swiftnav/src/nmea/checksum.rs b/swiftnav/src/nmea/checksum.rs
index ee3d00e..dca8298 100644
--- a/swiftnav/src/nmea/checksum.rs
+++ b/swiftnav/src/nmea/checksum.rs
@@ -25,16 +25,17 @@ fn u8_to_ascii_char(nibble: u8) -> char {
 pub fn calculate_checksum(sentence: &str) -> String {
     let mut checksum = 0;
 
-    let mut at_checksum_validation_value = false;
+    // this flag indicates if we have reached the '*' character or anything beyond that such as the actual checksum value or the end sequence (<CR><LF>)
+    let mut at_or_past_checksum_field = false;
 
     for (i, byte) in sentence.bytes().enumerate() {
         // Skip the starting '$' and the '*' before the checksum
-        if (i == 0 && byte == b'$') || at_checksum_validation_value {
+        if (i == 0 && byte == b'$') || at_or_past_checksum_field {
             continue;
         }
 
         if byte == b'*' {
-            at_checksum_validation_value = true;
+            at_or_past_checksum_field = true;
             continue;
         }
 

From 9980a32f7c86312787fc6b04d0084bf328772ed0 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 11:10:06 -0700
Subject: [PATCH 08/17] make sure to zero out top 4 bits in high nibble

---
 swiftnav/src/nmea/checksum.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/swiftnav/src/nmea/checksum.rs b/swiftnav/src/nmea/checksum.rs
index dca8298..6d4a3bc 100644
--- a/swiftnav/src/nmea/checksum.rs
+++ b/swiftnav/src/nmea/checksum.rs
@@ -1,7 +1,7 @@
 fn u8_to_nibbles(byte: u8) -> (u8, u8) {
     // The high nibble is obtained by shifting the byte 4 bits to the right.
     // This discards the lower 4 bits and moves the upper 4 bits into the lower 4 bit positions.
-    let high_nibble = byte >> 4;
+    let high_nibble = (byte >> 4) & 0x0F;
 
     // The low nibble is obtained by masking the byte with 0x0F (binary 0000_1111).
     // This keeps only the lower 4 bits and sets the upper 4 bits to zero.

From d6f49f65e85caef69dbb7dded71965a05f8c2e0f Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 11:27:53 -0700
Subject: [PATCH 09/17] add test for gga sentence len

---
 swiftnav/src/nmea/gga.rs | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/swiftnav/src/nmea/gga.rs b/swiftnav/src/nmea/gga.rs
index bebaea6..851f936 100644
--- a/swiftnav/src/nmea/gga.rs
+++ b/swiftnav/src/nmea/gga.rs
@@ -126,12 +126,14 @@ impl GGA {
         };
 
         let sentence = format!(
-            "$GPGGA,{timestamp},{latitude:.6},{latitudinal_hemisphere},{longitude:.6},{longitudinal_hemisphere},{gps_quality},{sat_in_use},{hdop:.1},{height:.6},M,{geoidal_separation},{age_dgps:.1},{dgps_station_id}",
+            "GPGGA,{timestamp},{latitude:.6},{latitudinal_hemisphere},{longitude:.6},{longitudinal_hemisphere},{gps_quality},{sat_in_use},{hdop:.1},{height:.6},M,{geoidal_separation},{age_dgps:.1},{dgps_station_id}",
         );
 
         let checksum = nmea::calculate_checksum(&sentence);
 
-        format!("{sentence}*{checksum}\r\n")
+        let sentence = format!("${sentence}*{checksum}\r\n");
+
+        sentence
     }
 }
 
@@ -197,4 +199,27 @@ mod test {
             "$GPGGA,0189.00,34.052200,N,-118.243700,W,1,8,1.2,0.0,M,1.00,,*00\r\n"
         );
     }
+
+    #[test]
+    fn gga_sentence_is_always_less_than_82_characters() {
+        // we are going to set some very large decimal places and the highest possible values in terms of character count to ensure our sentence is always below 82 characters
+        let gga = GGA::builder()
+            .sat_in_use(12)
+            .time(DateTime::from_timestamp(1_761_351_489, 0).unwrap())
+            .hdop(1.210_123_1)
+            .llh(super::LLHDegrees::new(
+                -90.000_000_001,
+                -180.000_000_000_1,
+                1_000.000_000_000,
+            ))
+            .gps_quality(GPSQuality::DGPS)
+            .age_dgps(Duration::from_secs_f64(2.500_000_000_001))
+            .geoidal_separation(1.00)
+            .dgps_station_id(1023) // 1023 is the max value for a 4 digit station ID
+            .build();
+
+        let sentence = gga.to_sentence();
+
+        assert!(sentence.len() < 82);
+    }
 }

From e12b6db7cba515f878bdd623a54bdad3026a24f1 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 11:46:04 -0700
Subject: [PATCH 10/17] update option for gga

---
 swiftnav/src/nmea/gga.rs | 42 ++++++++++++++--------------------------
 1 file changed, 14 insertions(+), 28 deletions(-)

diff --git a/swiftnav/src/nmea/gga.rs b/swiftnav/src/nmea/gga.rs
index 851f936..8adcf69 100644
--- a/swiftnav/src/nmea/gga.rs
+++ b/swiftnav/src/nmea/gga.rs
@@ -53,27 +53,24 @@ impl fmt::Display for GPSQuality {
 /// Geographic coordinates including altitude, GPS solution quality, DGPS usage information.
 #[derive(Debug, PartialEq, Clone, Builder)]
 pub struct GGA {
-    /// Navigational system.
-    #[builder(default = Source::GPS)]
-    pub source: Source,
     /// Time of fix in UTC.
     #[builder(default = Utc::now())]
     pub time: DateTime<Utc>,
     /// Latitude, longitude and height in degrees.
     pub llh: LLHDegrees,
     /// Quality of GPS solution.
-    #[builder(default = GPSQuality::GPS)]
+    #[builder(default = GPSQuality::NoFix)]
     pub gps_quality: GPSQuality,
     /// Sattelites in use
-    pub sat_in_use: u8,
+    pub sat_in_use: Option<u8>,
     /// Horizontal dilusion of presicion
-    pub hdop: f32,
+    pub hdop: Option<f32>,
     /// The difference between reference ellipsoid surface and mean-sea-level.
     pub geoidal_separation: Option<f32>,
-    /// DGPS data age. None if DGPS not in use.
+    /// DGPS data age
     pub age_dgps: Option<Duration>,
-    /// ID of reference DGPS station used for fix. None if DGPS not in use.
-    pub dgps_station_id: Option<u16>,
+    /// ID of reference DGPS station used for fix
+    pub reference_station_id: Option<u16>,
 }
 
 impl GGA {
@@ -98,35 +95,24 @@ impl GGA {
 
         let gps_quality = self.gps_quality;
 
-        let sat_in_use = self.sat_in_use;
+        let sat_in_use = self.sat_in_use.map_or(String::new(), |sat| sat.to_string());
 
-        let hdop = self.hdop;
+        let hdop = self.hdop.map_or(String::new(), |hdop| format!("{hdop:.1}"));
 
         // NOTE(ted): This is actually not the right value to use, however, we don't really use height for finding information like nearest station so it's ok to use for now
         let height = "0.0";
 
-        // if DGPS is not used, this should be a null field
-        let age_dgps = if matches!(gps_quality, GPSQuality::DGPS) {
-            let age = self.age_dgps.map_or(0.0, |age| age.as_secs_f64());
-
-            format!("{age:.1}")
-        } else {
-            String::new()
-        };
+        let age_dgps = self.age_dgps.map_or(0.0, |age| age.as_secs_f64());
 
         let geoidal_separation = self
             .geoidal_separation
             .map_or(String::new(), |sep| format!("{sep:.2}"));
 
-        let dgps_station_id = if matches!(gps_quality, GPSQuality::DGPS) {
-            self.dgps_station_id
+        let reference_station_id = self.reference_station_id
                 .map_or(String::new(), |id| id.to_string())
-        } else {
-            String::new()
-        };
 
         let sentence = format!(
-            "GPGGA,{timestamp},{latitude:.6},{latitudinal_hemisphere},{longitude:.6},{longitudinal_hemisphere},{gps_quality},{sat_in_use},{hdop:.1},{height:.6},M,{geoidal_separation},{age_dgps:.1},{dgps_station_id}",
+            "GPGGA,{timestamp},{latitude:.6},{latitudinal_hemisphere},{longitude:.6},{longitudinal_hemisphere},{gps_quality},{sat_in_use},{hdop},{height:.6},M,{geoidal_separation},{age_dgps:.1},{reference_station_id}",
         );
 
         let checksum = nmea::calculate_checksum(&sentence);
@@ -168,7 +154,7 @@ mod test {
             .gps_quality(GPSQuality::DGPS)
             .age_dgps(Duration::from_secs_f64(2.5))
             .geoidal_separation(1.0)
-            .dgps_station_id(42)
+            .reference_station_id(42)
             .build();
 
         let sentence = gga.to_sentence();
@@ -189,7 +175,7 @@ mod test {
             .gps_quality(GPSQuality::GPS)
             .age_dgps(Duration::from_secs_f64(2.5))
             .geoidal_separation(1.0)
-            .dgps_station_id(42)
+            .reference_station_id(42)
             .build();
 
         let sentence = gga.to_sentence();
@@ -215,7 +201,7 @@ mod test {
             .gps_quality(GPSQuality::DGPS)
             .age_dgps(Duration::from_secs_f64(2.500_000_000_001))
             .geoidal_separation(1.00)
-            .dgps_station_id(1023) // 1023 is the max value for a 4 digit station ID
+            .reference_station_id(1023) // 1023 is the max value for a 4 digit station ID
             .build();
 
         let sentence = gga.to_sentence();

From d68e21b8ae9c5b0755a348dd4db1c5a459b4dbe3 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 11:46:34 -0700
Subject: [PATCH 11/17] fix typo

---
 swiftnav/src/nmea/gga.rs | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/swiftnav/src/nmea/gga.rs b/swiftnav/src/nmea/gga.rs
index 8adcf69..b0e2d52 100644
--- a/swiftnav/src/nmea/gga.rs
+++ b/swiftnav/src/nmea/gga.rs
@@ -8,7 +8,7 @@ use chrono::{DateTime, Timelike, Utc};
 
 use crate::{
     coords::LLHDegrees,
-    nmea::{self, Source},
+    nmea::{self},
 };
 
 /// Quality of GPS solution
@@ -108,8 +108,9 @@ impl GGA {
             .geoidal_separation
             .map_or(String::new(), |sep| format!("{sep:.2}"));
 
-        let reference_station_id = self.reference_station_id
-                .map_or(String::new(), |id| id.to_string())
+        let reference_station_id = self
+            .reference_station_id
+            .map_or(String::new(), |id| id.to_string());
 
         let sentence = format!(
             "GPGGA,{timestamp},{latitude:.6},{latitudinal_hemisphere},{longitude:.6},{longitudinal_hemisphere},{gps_quality},{sat_in_use},{hdop},{height:.6},M,{geoidal_separation},{age_dgps:.1},{reference_station_id}",

From 204de5096b1f8d074115fea9f329a091ae7b6cd5 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 18:59:57 +0000
Subject: [PATCH 12/17] rustfmt (#138)

---
 rustfmt.toml                        |  8 +++++++
 swiftnav/Cargo.toml                 |  4 ++--
 swiftnav/src/coords/ecef.rs         |  3 ++-
 swiftnav/src/coords/llh.rs          | 12 ++++++----
 swiftnav/src/coords/mod.rs          | 25 ++++++++++----------
 swiftnav/src/edc.rs                 |  3 ++-
 swiftnav/src/math.rs                | 15 ++++++------
 swiftnav/src/nmea/checksum.rs       |  3 ++-
 swiftnav/src/nmea/gga.rs            | 36 +++++++++--------------------
 swiftnav/src/nmea/source.rs         |  3 ++-
 swiftnav/src/reference_frame/mod.rs | 25 ++++++++++++--------
 swiftnav/src/signal/code.rs         |  2 +-
 swiftnav/src/signal/mod.rs          |  6 +++--
 swiftnav/src/time/gnss.rs           |  5 ++--
 swiftnav/src/time/mjd.rs            | 17 ++++++++++++--
 swiftnav/src/time/utc.rs            | 17 ++++++++++----
 16 files changed, 106 insertions(+), 78 deletions(-)
 create mode 100644 rustfmt.toml

diff --git a/rustfmt.toml b/rustfmt.toml
new file mode 100644
index 0000000..c9a1eda
--- /dev/null
+++ b/rustfmt.toml
@@ -0,0 +1,8 @@
+max_width = 100
+wrap_comments = true
+comment_width = 100
+format_strings = true
+edition = "2024"
+imports_granularity = "Crate"
+group_imports = "StdExternalCrate"
+style_edition = "2024"
diff --git a/swiftnav/Cargo.toml b/swiftnav/Cargo.toml
index 921349e..094d805 100644
--- a/swiftnav/Cargo.toml
+++ b/swiftnav/Cargo.toml
@@ -12,14 +12,14 @@ rust-version = "1.85.0"
 [dependencies]
 bon = "3.8.1"
 rustversion = "1.0.22"
-chrono = { version = "0.4.42", optional = true }
+chrono = { version = "0.4.42" }
 strum = { version = "0.27.2", features = ["derive"] }
 nalgebra = "0.34.1"
 thiserror = "2.0.17"
 
 [dev-dependencies]
 float_eq = "1.0.1"
-proptest = "1.8.0"
+proptest = "1.9.0"
 
 # This tells docs.rs to include the katex header for math formatting
 # To do this locally 
diff --git a/swiftnav/src/coords/ecef.rs b/swiftnav/src/coords/ecef.rs
index 9774214..8ef2038 100644
--- a/swiftnav/src/coords/ecef.rs
+++ b/swiftnav/src/coords/ecef.rs
@@ -1,6 +1,7 @@
-use nalgebra::Vector3;
 use std::ops::{Add, AddAssign, Mul, MulAssign, Sub, SubAssign};
 
+use nalgebra::Vector3;
+
 use crate::{
     coords::{AzimuthElevation, Ellipsoid, LLHDegrees, LLHRadians, NED, WGS84},
     math,
diff --git a/swiftnav/src/coords/llh.rs b/swiftnav/src/coords/llh.rs
index 58b03b3..beec5e7 100644
--- a/swiftnav/src/coords/llh.rs
+++ b/swiftnav/src/coords/llh.rs
@@ -1,11 +1,12 @@
-use crate::coords::{LatitudinalHemisphere, LongitudinalHemisphere};
-
-use super::{Ellipsoid, ECEF, WGS84};
 use nalgebra::Vector3;
 
+use super::{ECEF, Ellipsoid, WGS84};
+use crate::coords::{LatitudinalHemisphere, LongitudinalHemisphere};
+
 /// WGS84 geodetic coordinates (Latitude, Longitude, Height), with angles in degrees.
 ///
-/// Internally stored as an array of 3 [f64](std::f64) values: latitude, longitude, and height above the ellipsoid in meters
+/// Internally stored as an array of 3 [f64](std::f64) values: latitude, longitude, and height above
+/// the ellipsoid in meters
 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Default)]
 pub struct LLHDegrees(Vector3<f64>);
 
@@ -157,7 +158,8 @@ impl AsMut<Vector3<f64>> for LLHDegrees {
 
 /// WGS84 geodetic coordinates (Latitude, Longitude, Height), with angles in radians.
 ///
-/// Internally stored as an array of 3 [f64](std::f64) values: latitude, longitude, and height above the ellipsoid in meters
+/// Internally stored as an array of 3 [f64](std::f64) values: latitude, longitude, and height above
+/// the ellipsoid in meters
 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Default)]
 pub struct LLHRadians(Vector3<f64>);
 
diff --git a/swiftnav/src/coords/mod.rs b/swiftnav/src/coords/mod.rs
index fb3d202..804bae7 100644
--- a/swiftnav/src/coords/mod.rs
+++ b/swiftnav/src/coords/mod.rs
@@ -44,11 +44,10 @@
 //! the more common algortihms based on the Newton-Raphson method.
 //!
 //! ## References
-//! * "A comparison of methods used in rectangular to Geodetic Coordinates
-//!   Transformations", Burtch R. R. (2006), American Congress for Surveying
-//!   and Mapping Annual Conference. Orlando, Florida.
-//! * "Transformation from Cartesian to Geodetic Coordinates Accelerated by
-//!   Halley’s Method", T. Fukushima (2006), Journal of Geodesy.
+//! * "A comparison of methods used in rectangular to Geodetic Coordinates Transformations", Burtch
+//!   R. R. (2006), American Congress for Surveying and Mapping Annual Conference. Orlando, Florida.
+//! * "Transformation from Cartesian to Geodetic Coordinates Accelerated by Halley’s Method", T.
+//!   Fukushima (2006), Journal of Geodesy.
 //!
 //! # Examples
 //!
@@ -84,16 +83,19 @@ pub use ecef::*;
 pub use ellipsoid::*;
 pub use hemisphere::*;
 pub use llh::*;
+use nalgebra::Vector2;
 pub use ned::*;
 
 use crate::{reference_frame::ReferenceFrame, time::GpsTime};
-use nalgebra::Vector2;
 
-/// WGS84 local horizontal coordinates consisting of an Azimuth and Elevation, with angles stored as radians
+/// WGS84 local horizontal coordinates consisting of an Azimuth and Elevation, with angles stored as
+/// radians
 ///
-/// Azimuth can range from $0$ to $2\pi$. North has an azimuth of $0$, east has an azimuth of $\frac{\pi}{2}$
+/// Azimuth can range from $0$ to $2\pi$. North has an azimuth of $0$, east has an azimuth of
+/// $\frac{\pi}{2}$
 ///
-/// Elevation can range from $-\frac{\pi}{2}$ to $\frac{\pi}{2}$. Up has an elevation of $\frac{\pi}{2}$, down an elevation of $-\frac{\pi}{2}$
+/// Elevation can range from $-\frac{\pi}{2}$ to $\frac{\pi}{2}$. Up has an elevation of
+/// $\frac{\pi}{2}$, down an elevation of $-\frac{\pi}{2}$
 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Default)]
 pub struct AzimuthElevation(Vector2<f64>);
 
@@ -292,11 +294,10 @@ impl Coordinate {
 #[cfg(test)]
 mod tests {
     use float_eq::assert_float_eq;
-
-    use crate::time::UtcTime;
+    use proptest::prelude::*;
 
     use super::*;
-    use proptest::prelude::*;
+    use crate::time::UtcTime;
 
     /* Maximum allowable error in quantities with units of length (in meters). */
     const MAX_DIST_ERROR_M: f64 = 1e-6;
diff --git a/swiftnav/src/edc.rs b/swiftnav/src/edc.rs
index c593e3b..402f0d4 100644
--- a/swiftnav/src/edc.rs
+++ b/swiftnav/src/edc.rs
@@ -326,9 +326,10 @@ pub fn compute_crc24q(buf: &[u8], initial_value: u32) -> u32 {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use proptest::prelude::*;
 
+    use super::*;
+
     const TEST_DATA: &[u8] = "123456789".as_bytes();
 
     /// Helper function to append a CRC-24Q value as 3 bytes (big-endian) to a buffer
diff --git a/swiftnav/src/math.rs b/swiftnav/src/math.rs
index 47977fb..38026d8 100644
--- a/swiftnav/src/math.rs
+++ b/swiftnav/src/math.rs
@@ -10,11 +10,7 @@
 
 /// We define a `const` max function since [`std::cmp::max`] isn't `const`
 pub(crate) const fn compile_time_max_u16(a: u16, b: u16) -> u16 {
-    if b < a {
-        a
-    } else {
-        b
-    }
+    if b < a { a } else { b }
 }
 
 /// Computes the square root of a given number at compile time using the Newton-Raphson method.
@@ -35,7 +31,8 @@ pub(crate) const fn compile_time_max_u16(a: u16, b: u16) -> u16 {
 /// # Notes
 ///
 /// - This function is marked as `const`, allowing it to be evaluated at compile time.
-/// - The algorithm iteratively refines the approximation of the square root until the result stabilizes.
+/// - The algorithm iteratively refines the approximation of the square root until the result
+///   stabilizes.
 #[expect(clippy::many_single_char_names, reason = "It's math, whatyagonnado?")]
 pub(crate) const fn compile_time_sqrt(s: f64) -> f64 {
     assert!(
@@ -57,7 +54,8 @@ pub(crate) const fn compile_time_sqrt(s: f64) -> f64 {
     x
 }
 
-/// Calculate the rotation matrix for rotating between an [`crate::coords::ECEF`] and [`crate::coords::NED`] frames
+/// Calculate the rotation matrix for rotating between an [`crate::coords::ECEF`] and
+/// [`crate::coords::NED`] frames
 #[must_use]
 pub(crate) fn ecef2ned_matrix(llh: crate::coords::LLHRadians) -> nalgebra::Matrix3<f64> {
     let sin_lat = llh.latitude().sin();
@@ -80,10 +78,11 @@ pub(crate) fn ecef2ned_matrix(llh: crate::coords::LLHRadians) -> nalgebra::Matri
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use float_eq::assert_float_eq;
     use proptest::prelude::*;
 
+    use super::*;
+
     proptest! {
         #![proptest_config(ProptestConfig::with_cases(1000))]
 
diff --git a/swiftnav/src/nmea/checksum.rs b/swiftnav/src/nmea/checksum.rs
index 6d4a3bc..1a6e5e1 100644
--- a/swiftnav/src/nmea/checksum.rs
+++ b/swiftnav/src/nmea/checksum.rs
@@ -25,7 +25,8 @@ fn u8_to_ascii_char(nibble: u8) -> char {
 pub fn calculate_checksum(sentence: &str) -> String {
     let mut checksum = 0;
 
-    // this flag indicates if we have reached the '*' character or anything beyond that such as the actual checksum value or the end sequence (<CR><LF>)
+    // this flag indicates if we have reached the '*' character or anything beyond that such as the
+    // actual checksum value or the end sequence (<CR><LF>)
     let mut at_or_past_checksum_field = false;
 
     for (i, byte) in sentence.bytes().enumerate() {
diff --git a/swiftnav/src/nmea/gga.rs b/swiftnav/src/nmea/gga.rs
index b0e2d52..292ff8b 100644
--- a/swiftnav/src/nmea/gga.rs
+++ b/swiftnav/src/nmea/gga.rs
@@ -99,10 +99,13 @@ impl GGA {
 
         let hdop = self.hdop.map_or(String::new(), |hdop| format!("{hdop:.1}"));
 
-        // NOTE(ted): This is actually not the right value to use, however, we don't really use height for finding information like nearest station so it's ok to use for now
+        // NOTE(ted): This is actually not the right value to use, however, we don't really use
+        // height for finding information like nearest station so it's ok to use for now
         let height = "0.0";
 
-        let age_dgps = self.age_dgps.map_or(0.0, |age| age.as_secs_f64());
+        let age_dgps = self
+            .age_dgps
+            .map_or(String::new(), |age| format!("{:.1}", age.as_secs_f64()));
 
         let geoidal_separation = self
             .geoidal_separation
@@ -113,7 +116,9 @@ impl GGA {
             .map_or(String::new(), |id| id.to_string());
 
         let sentence = format!(
-            "GPGGA,{timestamp},{latitude:.6},{latitudinal_hemisphere},{longitude:.6},{longitudinal_hemisphere},{gps_quality},{sat_in_use},{hdop},{height:.6},M,{geoidal_separation},{age_dgps:.1},{reference_station_id}",
+            "GPGGA,{timestamp},{latitude:.6},{latitudinal_hemisphere},{longitude:.6},\
+             {longitudinal_hemisphere},{gps_quality},{sat_in_use},{hdop},{height:.6},M,\
+             {geoidal_separation},{age_dgps:.1},{reference_station_id}",
         );
 
         let checksum = nmea::calculate_checksum(&sentence);
@@ -133,6 +138,7 @@ mod test {
         let gga = GGA::builder()
             .sat_in_use(12)
             .time(DateTime::from_timestamp(1_761_351_489, 0).unwrap())
+            .gps_quality(GPSQuality::GPS)
             .hdop(0.9)
             .llh(super::LLHDegrees::new(37.7749, -122.4194, 10.0))
             .build();
@@ -166,30 +172,10 @@ mod test {
         );
     }
 
-    #[test]
-    fn gga_with_dgps_fields_that_is_not_dgps_is_ignored() {
-        let gga = GGA::builder()
-            .sat_in_use(8)
-            .time(DateTime::from_timestamp(1_761_351_489, 0).unwrap())
-            .hdop(1.2)
-            .llh(super::LLHDegrees::new(34.0522, -118.2437, 15.0))
-            .gps_quality(GPSQuality::GPS)
-            .age_dgps(Duration::from_secs_f64(2.5))
-            .geoidal_separation(1.0)
-            .reference_station_id(42)
-            .build();
-
-        let sentence = gga.to_sentence();
-
-        assert_eq!(
-            sentence,
-            "$GPGGA,0189.00,34.052200,N,-118.243700,W,1,8,1.2,0.0,M,1.00,,*00\r\n"
-        );
-    }
-
     #[test]
     fn gga_sentence_is_always_less_than_82_characters() {
-        // we are going to set some very large decimal places and the highest possible values in terms of character count to ensure our sentence is always below 82 characters
+        // we are going to set some very large decimal places and the highest possible values in
+        // terms of character count to ensure our sentence is always below 82 characters
         let gga = GGA::builder()
             .sat_in_use(12)
             .time(DateTime::from_timestamp(1_761_351_489, 0).unwrap())
diff --git a/swiftnav/src/nmea/source.rs b/swiftnav/src/nmea/source.rs
index 1462bad..ea1f037 100644
--- a/swiftnav/src/nmea/source.rs
+++ b/swiftnav/src/nmea/source.rs
@@ -9,7 +9,8 @@ pub enum Source {
     Gallileo = 0b100,
     /// China's Beidou
     Beidou = 0b1000,
-    /// Global Navigation Sattelite System. Some combination of other systems. Depends on receiver model, receiver settings, etc..
+    /// Global Navigation Sattelite System. Some combination of other systems. Depends on receiver
+    /// model, receiver settings, etc..
     GNSS = 0b10000,
     /// `MediaTek` NMEA packet protocol
     MTK = 0b10_0000,
diff --git a/swiftnav/src/reference_frame/mod.rs b/swiftnav/src/reference_frame/mod.rs
index 208e11a..9a5f08b 100644
--- a/swiftnav/src/reference_frame/mod.rs
+++ b/swiftnav/src/reference_frame/mod.rs
@@ -9,9 +9,9 @@
 // WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
 //! Geodetic reference frame transformations
 //!
-//! Transform coordinates between geodetic reference frames using time-dependent Helmert transformations.
-//! Supports both global frames (ITRF series) and regional frames (ETRF, NAD83, etc.) with runtime
-//! parameter loading.
+//! Transform coordinates between geodetic reference frames using time-dependent Helmert
+//! transformations. Supports both global frames (ITRF series) and regional frames (ETRF, NAD83,
+//! etc.) with runtime parameter loading.
 //!
 //! # Key Concepts
 //!
@@ -68,14 +68,16 @@
 //! repo.add_transformation(custom_transform);
 //! ```
 
-use crate::coords::{Coordinate, ECEF};
-use nalgebra::{Matrix3, Vector3};
 use std::{
     collections::{HashMap, HashSet, VecDeque},
     fmt,
 };
+
+use nalgebra::{Matrix3, Vector3};
 use strum::{Display, EnumIter, EnumString};
 
+use crate::coords::{Coordinate, ECEF};
+
 mod params;
 
 /// Geodetic reference frame identifiers
@@ -195,10 +197,10 @@ impl PartialEq<ReferenceFrame> for &ReferenceFrame {
 /// # Parameter Units
 ///
 /// Input parameters are stored in standard geodetic units:
-/// - **Translation** (`tx`, `ty`, `tz`): millimeters (mm)  
+/// - **Translation** (`tx`, `ty`, `tz`): millimeters (mm)
 /// - **Translation rates** (`tx_dot`, `ty_dot`, `tz_dot`): mm/year
 /// - **Scale** (`s`): parts per billion (ppb)
-/// - **Scale rate** (`s_dot`): ppb/year  
+/// - **Scale rate** (`s_dot`): ppb/year
 /// - **Rotation** (`rx`, `ry`, `rz`): milliarcseconds (mas)
 /// - **Rotation rates** (`rx_dot`, `ry_dot`, `rz_dot`): mas/year
 /// - **Reference epoch** (`epoch`): decimal years
@@ -258,7 +260,8 @@ impl TimeDependentHelmertParams {
         }
     }
 
-    /// Reverses the transformation. Since this is a linear transformation we simply negate all terms
+    /// Reverses the transformation. Since this is a linear transformation we simply negate all
+    /// terms
     #[must_use]
     pub fn invert(mut self) -> Self {
         self.t *= -1.0;
@@ -574,10 +577,12 @@ fn builtin_transformations() -> Vec<Transformation> {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
+    use std::str::FromStr;
+
     use float_eq::assert_float_eq;
     use params::TRANSFORMATIONS;
-    use std::str::FromStr;
+
+    use super::*;
 
     #[expect(clippy::too_many_lines)]
     #[test]
diff --git a/swiftnav/src/signal/code.rs b/swiftnav/src/signal/code.rs
index 2d90814..1339dc1 100644
--- a/swiftnav/src/signal/code.rs
+++ b/swiftnav/src/signal/code.rs
@@ -8,7 +8,7 @@
 // EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
 // WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
 
-use super::{consts, Constellation};
+use super::{Constellation, consts};
 
 /// Code identifiers
 #[derive(
diff --git a/swiftnav/src/signal/mod.rs b/swiftnav/src/signal/mod.rs
index e1a3c0d..3722519 100644
--- a/swiftnav/src/signal/mod.rs
+++ b/swiftnav/src/signal/mod.rs
@@ -16,7 +16,8 @@
 //! This module provides:
 //! - [`Constellation`] - Representing the supporting GNSS constellations
 //! - [`Code`] - Representing the codes broadcast from the GNSS satellites
-//! - [`GnssSignal`] - Represents a [`Code`] broadcast by a specific satellite, using the satellite PRN as the identifier
+//! - [`GnssSignal`] - Represents a [`Code`] broadcast by a specific satellite, using the satellite
+//!   PRN as the identifier
 //!
 //! # Examples
 //!
@@ -37,9 +38,10 @@ mod code;
 mod constellation;
 pub mod consts;
 
+use std::fmt;
+
 pub use code::*;
 pub use constellation::*;
-use std::fmt;
 
 /// GNSS Signal identifier
 #[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
diff --git a/swiftnav/src/time/gnss.rs b/swiftnav/src/time/gnss.rs
index 4b9b9eb..ddb4f6c 100644
--- a/swiftnav/src/time/gnss.rs
+++ b/swiftnav/src/time/gnss.rs
@@ -7,12 +7,13 @@
 // THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
 // EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
 // WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
-use crate::time::{consts, UtcParams, UtcTime, MJD, UTC_LEAPS, WEEK};
 use std::{
     ops::{Add, AddAssign, Sub, SubAssign},
     time::Duration,
 };
 
+use crate::time::{MJD, UTC_LEAPS, UtcParams, UtcTime, WEEK, consts};
+
 /// Representation of GPS Time
 #[derive(Debug, Copy, Clone)]
 pub struct GpsTime {
@@ -189,7 +190,7 @@ impl GpsTime {
             assert!(utc_time.hour() == 23);
             assert!(utc_time.minute() == 59);
             assert!(utc_time.seconds_int() == 59);
-            /* add the extra second back in*/
+            /* add the extra second back in */
             utc_time.add_second();
         }
 
diff --git a/swiftnav/src/time/mjd.rs b/swiftnav/src/time/mjd.rs
index 197b34e..21a7156 100644
--- a/swiftnav/src/time/mjd.rs
+++ b/swiftnav/src/time/mjd.rs
@@ -15,9 +15,10 @@
     reason = "We need to review the math for overflows"
 )]
 
-use crate::time::{consts, GpsTime, UtcParams, UtcTime};
 use std::time::Duration;
 
+use crate::time::{GpsTime, UtcParams, UtcTime, consts};
+
 /// Representation of modified julian dates (MJD)
 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd)]
 pub struct MJD(f64);
@@ -51,7 +52,19 @@ impl MJD {
     #[must_use]
     pub fn from_parts(year: u16, month: u8, day: u8, hour: u8, minute: u8, seconds: f64) -> MJD {
         // Enforce our assumption that the date is just the MJD period
-        assert!(year > 1858 || (year == 1858 && month > 11) || (year == 1858 && month == 11 && day >= 17), "Attempting to convert a date prior to the start of the Modified Julian Date system ({}-{}-{}T{}:{}:{}Z", year, month, day, hour, minute, seconds);
+        assert!(
+            year > 1858
+                || (year == 1858 && month > 11)
+                || (year == 1858 && month == 11 && day >= 17),
+            "Attempting to convert a date prior to the start of the Modified Julian Date system \
+             ({}-{}-{}T{}:{}:{}Z",
+            year,
+            month,
+            day,
+            hour,
+            minute,
+            seconds
+        );
 
         let full_days = 367 * i64::from(year)
             - 7 * (i64::from(year) + (i64::from(month) + 9) / 12) / 4
diff --git a/swiftnav/src/time/utc.rs b/swiftnav/src/time/utc.rs
index 3547a3c..1ea9f6f 100644
--- a/swiftnav/src/time/utc.rs
+++ b/swiftnav/src/time/utc.rs
@@ -10,9 +10,10 @@
 
 #![allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
 
-use crate::time::{consts, is_leap_year, GpsTime, MJD};
 use std::time::Duration;
 
+use crate::time::{GpsTime, MJD, consts, is_leap_year};
+
 /// GPS UTC correction parameters
 #[derive(Clone)]
 pub struct UtcParams {
@@ -399,7 +400,6 @@ impl From<MJD> for UtcTime {
     }
 }
 
-#[cfg(feature = "chrono")]
 impl From<UtcTime> for chrono::DateTime<chrono::offset::Utc> {
     fn from(utc: UtcTime) -> chrono::DateTime<chrono::offset::Utc> {
         use chrono::prelude::*;
@@ -425,7 +425,6 @@ impl From<UtcTime> for chrono::DateTime<chrono::offset::Utc> {
     }
 }
 
-#[cfg(feature = "chrono")]
 impl<Tz: chrono::offset::TimeZone> From<chrono::DateTime<Tz>> for UtcTime {
     fn from(chrono: chrono::DateTime<Tz>) -> UtcTime {
         use chrono::prelude::*;
@@ -557,7 +556,16 @@ mod tests {
 
             #[expect(clippy::float_cmp)]
             {
-                assert!(d_utc == test_case.d_utc && is_lse == test_case.is_lse, "test_case.t: {:?}, test_case.d_utc: {}, test_case.is_lse: {}, d_utc: {}, is_lse: {}", test_case.t, test_case.d_utc, test_case.is_lse, d_utc, is_lse);
+                assert!(
+                    d_utc == test_case.d_utc && is_lse == test_case.is_lse,
+                    "test_case.t: {:?}, test_case.d_utc: {}, test_case.is_lse: {}, d_utc: {}, \
+                     is_lse: {}",
+                    test_case.t,
+                    test_case.d_utc,
+                    test_case.is_lse,
+                    d_utc,
+                    is_lse
+                );
             }
         }
     }
@@ -1090,7 +1098,6 @@ mod tests {
         }
     }
 
-    #[cfg(feature = "chrono")]
     #[test]
     fn chrono_conversions() {
         use chrono::prelude::*;

From 39b27c7a98ac983830077c3ad620e4ab39351443 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 12:01:18 -0700
Subject: [PATCH 13/17] add more checksum examples

---
 swiftnav/src/nmea/checksum.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/swiftnav/src/nmea/checksum.rs b/swiftnav/src/nmea/checksum.rs
index 1a6e5e1..669abe9 100644
--- a/swiftnav/src/nmea/checksum.rs
+++ b/swiftnav/src/nmea/checksum.rs
@@ -58,6 +58,14 @@ mod tests {
         let sentence = "GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,";
         let checksum = super::calculate_checksum(sentence);
         assert_eq!(checksum, "47");
+
+        let sentence = "$GPGLL,5057.970,N,00146.110,E,142451,A";
+        let checksum = super::calculate_checksum(sentence);
+        assert_eq!(checksum, "27");
+
+        let sentence = "$GPVTG,089.0,T,,,15.2,N,,";
+        let checksum = super::calculate_checksum(sentence);
+        assert_eq!(checksum, "7F");
     }
 
     #[test]

From 3a2e70aacc561ba1382f50ec08d41b6bf57602a6 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 13:27:26 -0700
Subject: [PATCH 14/17] fix gga sentence

---
 .github/workflows/ci.yaml     |  2 +-
 Cargo.toml                    |  6 ++----
 swiftnav/Cargo.toml           |  4 ++--
 swiftnav/src/coords/llh.rs    | 32 ++++++++++++++++++++++++++++++
 swiftnav/src/coords/mod.rs    |  4 ++--
 swiftnav/src/edc.rs           |  9 +++------
 swiftnav/src/nmea/checksum.rs |  9 ++-------
 swiftnav/src/nmea/gga.rs      | 31 +++++++++++++++--------------
 swiftnav/src/nmea/mod.rs      |  2 --
 swiftnav/src/nmea/source.rs   | 17 ----------------
 swiftnav/src/time/mjd.rs      |  8 +-------
 swiftnav/src/time/mod.rs      | 37 +++++++++++------------------------
 12 files changed, 72 insertions(+), 89 deletions(-)
 delete mode 100644 swiftnav/src/nmea/source.rs

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index cd18201..1cd5352 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -65,7 +65,7 @@ jobs:
           # MSRV
           - os: ubuntu-latest
             binary_target: x86_64-unknown-linux-gnu
-            toolchain: 1.90.0
+            toolchain: 1.87.0
     steps:
       - uses: actions/checkout@v5
         with:
diff --git a/Cargo.toml b/Cargo.toml
index f5c4cc1..dc3fda2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,5 +1,3 @@
 [workspace]
-members = [
-    "swiftnav",
-    # "swiftnav-sys"
-]
+resolver = "3"
+members = ["swiftnav"]
diff --git a/swiftnav/Cargo.toml b/swiftnav/Cargo.toml
index 094d805..7880145 100644
--- a/swiftnav/Cargo.toml
+++ b/swiftnav/Cargo.toml
@@ -2,12 +2,12 @@
 name = "swiftnav"
 version = "0.10.0"
 authors = ["Swift Navigation <dev@swiftnav.com>"]
-edition = "2018"
+edition = "2024"
 description = "GNSS positioning and related utilities"
 readme = "README.md"
 repository = "https://github.com/swift-nav/swiftnav-rs"
 license = "LGPL-3.0"
-rust-version = "1.85.0"
+rust-version = "1.87.0"
 
 [dependencies]
 bon = "3.8.1"
diff --git a/swiftnav/src/coords/llh.rs b/swiftnav/src/coords/llh.rs
index beec5e7..6e8e61d 100644
--- a/swiftnav/src/coords/llh.rs
+++ b/swiftnav/src/coords/llh.rs
@@ -47,6 +47,22 @@ impl LLHDegrees {
         self.0.x
     }
 
+    /// Get the latitude in degrees and decimal minutes
+    #[must_use]
+    pub fn latitude_degree_decimal_minutes(&self) -> (u16, f64) {
+        let lat = self.latitude();
+
+        #[expect(
+            clippy::cast_possible_truncation,
+            clippy::cast_sign_loss,
+            reason = "We are using trunc() and abs() already to remove the fractional part"
+        )]
+        let degrees = lat.trunc().abs() as u16;
+        let minutes = lat.fract().abs() * 60.0;
+
+        (degrees, minutes)
+    }
+
     /// Get the latitudinal hemisphere
     #[must_use]
     pub fn latitudinal_hemisphere(&self) -> LatitudinalHemisphere {
@@ -63,6 +79,22 @@ impl LLHDegrees {
         self.0.y
     }
 
+    /// Get the latitude in degrees and decimal minutes
+    #[must_use]
+    pub fn longitude_degree_decimal_minutes(&self) -> (u16, f64) {
+        let lon = self.longitude();
+
+        #[expect(
+            clippy::cast_possible_truncation,
+            clippy::cast_sign_loss,
+            reason = "We are using trunc() and abs() already to remove the fractional part"
+        )]
+        let degrees = lon.trunc().abs() as u16;
+        let minutes = lon.fract().abs() * 60.0;
+
+        (degrees, minutes)
+    }
+
     /// Get the longitudinal hemisphere
     #[must_use]
     pub fn longitudinal_hemisphere(&self) -> LongitudinalHemisphere {
diff --git a/swiftnav/src/coords/mod.rs b/swiftnav/src/coords/mod.rs
index 804bae7..f8bab7c 100644
--- a/swiftnav/src/coords/mod.rs
+++ b/swiftnav/src/coords/mod.rs
@@ -538,11 +538,11 @@ mod tests {
 
             let lat_err = llh_input.latitude() - llh_output.latitude();
             assert!(lat_err.abs() < MAX_ANGLE_ERROR_RAD,
-                "Converting random WGS84 LLH to ECEF and back again does not return the original values. Initial: {:?}, ECEF: {:?}, Final: {:?}, Lat error (rad): {}", llh_input, ecef, llh_output, lat_err);
+                "Converting random WGS84 LLH to ECEF and back again does not return the original values. Initial: {llh_input:?}, ECEF: {ecef:?}, Final: {llh_output:?}, Lat error (rad): {lat_err}");
 
             let lon_err = llh_input.longitude() - llh_output.longitude();
             assert!(lon_err.abs() < MAX_ANGLE_ERROR_RAD,
-                "Converting random WGS84 LLH to ECEF and back again does not return the original values. Initial: {:?}, ECEF: {:?}, Final: {:?}, Lon error (rad): {}", llh_input, ecef, llh_output, lon_err);
+                "Converting random WGS84 LLH to ECEF and back again does not return the original values. Initial: {llh_input:?}, ECEF: {ecef:?}, Final: {llh_output:?}, Lon error (rad): {lon_err}");
 
             let hgt_err = llh_input.height() - llh_output.height();
             assert!(hgt_err.abs() < MAX_DIST_ERROR_M,
diff --git a/swiftnav/src/edc.rs b/swiftnav/src/edc.rs
index 402f0d4..5d8f841 100644
--- a/swiftnav/src/edc.rs
+++ b/swiftnav/src/edc.rs
@@ -354,15 +354,13 @@ mod tests {
         let crc = compute_crc24q(&TEST_DATA[0..0], 0);
         assert!(
             crc == 0,
-            "CRC of empty buffer with starting value 0 should be 0, not {}",
-            crc
+            "CRC of empty buffer with starting value 0 should be 0, not {crc}",
         );
 
         let crc = compute_crc24q(&TEST_DATA[0..0], 22);
         assert!(
             crc == 22,
-            "CRC of empty buffer with starting value 22 should be 22, not {}",
-            crc
+            "CRC of empty buffer with starting value 22 should be 22, not {crc}",
         );
 
         /* Test value taken from python crcmod package tests, see:
@@ -370,8 +368,7 @@ mod tests {
         let crc = compute_crc24q(TEST_DATA, 0x00B7_04CE);
         assert!(
             crc == 0x0021_CF02,
-            "CRC of \"123456789\" with init value 0xB704CE should be 0x21CF02, not {}",
-            crc
+            "CRC of \"123456789\" with init value 0xB704CE should be 0x21CF02, not {crc}",
         );
     }
 
diff --git a/swiftnav/src/nmea/checksum.rs b/swiftnav/src/nmea/checksum.rs
index 669abe9..ec8e64b 100644
--- a/swiftnav/src/nmea/checksum.rs
+++ b/swiftnav/src/nmea/checksum.rs
@@ -25,19 +25,14 @@ fn u8_to_ascii_char(nibble: u8) -> char {
 pub fn calculate_checksum(sentence: &str) -> String {
     let mut checksum = 0;
 
-    // this flag indicates if we have reached the '*' character or anything beyond that such as the
-    // actual checksum value or the end sequence (<CR><LF>)
-    let mut at_or_past_checksum_field = false;
-
     for (i, byte) in sentence.bytes().enumerate() {
         // Skip the starting '$' and the '*' before the checksum
-        if (i == 0 && byte == b'$') || at_or_past_checksum_field {
+        if i == 0 && byte == b'$' {
             continue;
         }
 
         if byte == b'*' {
-            at_or_past_checksum_field = true;
-            continue;
+            break;
         }
 
         checksum ^= byte;
diff --git a/swiftnav/src/nmea/gga.rs b/swiftnav/src/nmea/gga.rs
index 292ff8b..f445da9 100644
--- a/swiftnav/src/nmea/gga.rs
+++ b/swiftnav/src/nmea/gga.rs
@@ -12,12 +12,13 @@ use crate::{
 };
 
 /// Quality of GPS solution
-#[derive(Debug, PartialEq, Clone, Copy)]
+#[derive(Debug, PartialEq, Clone, Copy, Default)]
 pub enum GPSQuality {
     /// Fix not available or invalid
+    #[default]
     NoFix,
     /// GPS SPS Mode, fix valid
-    GPS,
+    SPS,
     /// Differential GPS, SPS Mode, fix valid
     DGPS,
     /// GPS PPS (pulse per second), fix valid
@@ -27,7 +28,7 @@ pub enum GPSQuality {
     /// Float RTK, satelite system used in RTK mode, floating integers
     FRTK,
     /// Estimated (dead reckoning) mode.
-    Estimated,
+    DeadReckoning,
     /// Manual input mode
     Manual,
     /// Simulated mode
@@ -38,12 +39,12 @@ impl fmt::Display for GPSQuality {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             GPSQuality::NoFix => write!(f, "0"),
-            GPSQuality::GPS => write!(f, "1"),
+            GPSQuality::SPS => write!(f, "1"),
             GPSQuality::DGPS => write!(f, "2"),
             GPSQuality::PPS => write!(f, "3"),
             GPSQuality::RTK => write!(f, "4"),
             GPSQuality::FRTK => write!(f, "5"),
-            GPSQuality::Estimated => write!(f, "6"),
+            GPSQuality::DeadReckoning => write!(f, "6"),
             GPSQuality::Manual => write!(f, "7"),
             GPSQuality::Simulated => write!(f, "8"),
         }
@@ -59,7 +60,7 @@ pub struct GGA {
     /// Latitude, longitude and height in degrees.
     pub llh: LLHDegrees,
     /// Quality of GPS solution.
-    #[builder(default = GPSQuality::NoFix)]
+    #[builder(default = GPSQuality::default())]
     pub gps_quality: GPSQuality,
     /// Sattelites in use
     pub sat_in_use: Option<u8>,
@@ -87,11 +88,11 @@ impl GGA {
 
         let timestamp = format!("{hour}{minute}{:.2}", second + second_fracs);
 
-        let latitude = self.llh.latitude();
-        let latitudinal_hemisphere = self.llh.latitudinal_hemisphere();
+        let (lat_deg, lat_mins) = self.llh.latitude_degree_decimal_minutes();
+        let lat_hemisphere = self.llh.latitudinal_hemisphere();
 
-        let longitude = self.llh.longitude();
-        let longitudinal_hemisphere = self.llh.longitudinal_hemisphere();
+        let (lon_deg, lon_mins) = self.llh.longitude_degree_decimal_minutes();
+        let lon_hemisphere = self.llh.longitudinal_hemisphere();
 
         let gps_quality = self.gps_quality;
 
@@ -116,8 +117,8 @@ impl GGA {
             .map_or(String::new(), |id| id.to_string());
 
         let sentence = format!(
-            "GPGGA,{timestamp},{latitude:.6},{latitudinal_hemisphere},{longitude:.6},\
-             {longitudinal_hemisphere},{gps_quality},{sat_in_use},{hdop},{height:.6},M,\
+            "GPGGA,{timestamp},{lat_deg:02}{lat_mins:010.7},{lat_hemisphere},{lon_deg:\
+             03}{lon_mins:010.7},{lon_hemisphere},{gps_quality},{sat_in_use},{hdop},{height:.6},M,\
              {geoidal_separation},{age_dgps:.1},{reference_station_id}",
         );
 
@@ -138,7 +139,7 @@ mod test {
         let gga = GGA::builder()
             .sat_in_use(12)
             .time(DateTime::from_timestamp(1_761_351_489, 0).unwrap())
-            .gps_quality(GPSQuality::GPS)
+            .gps_quality(GPSQuality::SPS)
             .hdop(0.9)
             .llh(super::LLHDegrees::new(37.7749, -122.4194, 10.0))
             .build();
@@ -147,7 +148,7 @@ mod test {
 
         assert_eq!(
             sentence,
-            "$GPGGA,0189.00,37.774900,N,-122.419400,W,1,12,0.9,0.0,M,,,*26\r\n"
+            "$GPGGA,0189.00,3746.4940000,N,12225.1640000,W,1,12,0.9,0.0,M,,,*01\r\n"
         );
     }
 
@@ -168,7 +169,7 @@ mod test {
 
         assert_eq!(
             sentence,
-            "$GPGGA,0189.00,34.052200,N,-118.243700,W,2,8,1.2,0.0,M,1.00,2,42*37\r\n"
+            "$GPGGA,0189.00,3403.1320000,N,11814.6220000,W,2,8,1.2,0.0,M,1.00,2,42*1D\r\n"
         );
     }
 
diff --git a/swiftnav/src/nmea/mod.rs b/swiftnav/src/nmea/mod.rs
index 8cdfef7..de97cdc 100644
--- a/swiftnav/src/nmea/mod.rs
+++ b/swiftnav/src/nmea/mod.rs
@@ -1,7 +1,5 @@
 mod checksum;
 mod gga;
-mod source;
 
 pub use checksum::*;
 pub use gga::*;
-pub use source::*;
diff --git a/swiftnav/src/nmea/source.rs b/swiftnav/src/nmea/source.rs
deleted file mode 100644
index ea1f037..0000000
--- a/swiftnav/src/nmea/source.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-/// Source of NMEA sentence like GPS, GLONASS or other.
-#[derive(Debug, Copy, Clone, PartialEq)]
-pub enum Source {
-    /// USA Global Positioning System
-    GPS = 0b1,
-    /// Russian Federation GLONASS
-    GLONASS = 0b10,
-    /// European Union Gallileo
-    Gallileo = 0b100,
-    /// China's Beidou
-    Beidou = 0b1000,
-    /// Global Navigation Sattelite System. Some combination of other systems. Depends on receiver
-    /// model, receiver settings, etc..
-    GNSS = 0b10000,
-    /// `MediaTek` NMEA packet protocol
-    MTK = 0b10_0000,
-}
diff --git a/swiftnav/src/time/mjd.rs b/swiftnav/src/time/mjd.rs
index 21a7156..c2565dd 100644
--- a/swiftnav/src/time/mjd.rs
+++ b/swiftnav/src/time/mjd.rs
@@ -57,13 +57,7 @@ impl MJD {
                 || (year == 1858 && month > 11)
                 || (year == 1858 && month == 11 && day >= 17),
             "Attempting to convert a date prior to the start of the Modified Julian Date system \
-             ({}-{}-{}T{}:{}:{}Z",
-            year,
-            month,
-            day,
-            hour,
-            minute,
-            seconds
+             ({year}-{month}-{day}T{hour}:{minute}:{seconds}Z"
         );
 
         let full_days = 367 * i64::from(year)
diff --git a/swiftnav/src/time/mod.rs b/swiftnav/src/time/mod.rs
index 0dc0788..6022986 100644
--- a/swiftnav/src/time/mod.rs
+++ b/swiftnav/src/time/mod.rs
@@ -79,7 +79,7 @@ pub const WEEK: Duration = Duration::from_secs(consts::WEEK_SECS as u64);
 /// All year values are treated as if they are in the Gregorian calendar
 #[must_use]
 pub fn is_leap_year(year: u16) -> bool {
-    ((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0)
+    (year.is_multiple_of(4) && !year.is_multiple_of(100)) || year.is_multiple_of(400)
 }
 
 #[cfg(test)]
@@ -119,11 +119,8 @@ mod tests {
             let diff = test_case.diff(&round_trip).abs();
             assert!(
                 diff < TOW_TOL,
-                "gps2mjd2gps failure. original: {:?}, round trip: {:?}, diff: {}, TOW_TOL: {}",
-                test_case,
-                round_trip,
-                diff,
-                TOW_TOL
+                "gps2mjd2gps failure. original: {test_case:?}, round trip: {round_trip:?}, diff: \
+                 {diff}, TOW_TOL: {TOW_TOL}"
             );
 
             // test mjd -> date -> mjd
@@ -132,11 +129,8 @@ mod tests {
             let diff = (mjd.as_f64() - round_trip.as_f64()).abs();
             assert!(
                 diff < TOW_TOL,
-                "mjd2date2mjd failure. original: {:?}, round trip: {:?}, diff: {}, TOW_TOL: {}",
-                mjd,
-                round_trip,
-                diff,
-                TOW_TOL
+                "mjd2date2mjd failure. original: {mjd:?}, round trip: {round_trip:?}, diff: \
+                 {diff}, TOW_TOL: {TOW_TOL}"
             );
 
             // test mjd -> utc -> mjd
@@ -145,11 +139,8 @@ mod tests {
             let diff = (mjd.as_f64() - round_trip.as_f64()).abs();
             assert!(
                 diff < TOW_TOL,
-                "mjd2utc2mjd failure. original: {:?}, round trip: {:?}, diff: {}, TOW_TOL: {}",
-                mjd,
-                round_trip,
-                diff,
-                TOW_TOL
+                "mjd2utc2mjd failure. original: {mjd:?}, round trip: {round_trip:?}, diff: \
+                 {diff}, TOW_TOL: {TOW_TOL}"
             );
 
             // test gps -> date -> gps
@@ -158,11 +149,8 @@ mod tests {
             let diff = test_case.diff(&round_trip).abs();
             assert!(
                 diff < TOW_TOL,
-                "gps2date2gps failure. original: {:?}, round trip: {:?}, diff: {}, TOW_TOL: {}",
-                test_case,
-                round_trip,
-                diff,
-                TOW_TOL
+                "gps2date2gps failure. original: {test_case:?}, round trip: {round_trip:?}, diff: \
+                 {diff}, TOW_TOL: {TOW_TOL}"
             );
 
             // test utc -> date -> utc
@@ -171,11 +159,8 @@ mod tests {
             let diff = utc.to_mjd().as_f64() - mjd.as_f64();
             assert!(
                 diff < TOW_TOL,
-                "utc2date2utc failure. original: {:?}, round trip: {:?}, diff: {}, TOW_TOL: {}",
-                mjd,
-                round_trip,
-                diff,
-                TOW_TOL
+                "utc2date2utc failure. original: {mjd:?}, round trip: {round_trip:?}, diff: \
+                 {diff}, TOW_TOL: {TOW_TOL}"
             );
         }
     }

From c33c12db25d274c76c710d56b56b137cfb5b287a Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 13:30:44 -0700
Subject: [PATCH 15/17] ensure we are formatting correctly by using a smaller
 lon

---
 swiftnav/src/nmea/gga.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/swiftnav/src/nmea/gga.rs b/swiftnav/src/nmea/gga.rs
index f445da9..2945a44 100644
--- a/swiftnav/src/nmea/gga.rs
+++ b/swiftnav/src/nmea/gga.rs
@@ -76,6 +76,7 @@ pub struct GGA {
 
 impl GGA {
     // converts the GGA struct into an NMEA sentence
+    // http://lefebure.com/articles/nmea-gga/
     #[must_use]
     pub fn to_sentence(&self) -> String {
         // NOTE(ted): We are formatting here a bit strange because for some ungodly reason,
@@ -158,7 +159,7 @@ mod test {
             .sat_in_use(8)
             .time(DateTime::from_timestamp(1_761_351_489, 0).unwrap())
             .hdop(1.2)
-            .llh(super::LLHDegrees::new(34.0522, -118.2437, 15.0))
+            .llh(super::LLHDegrees::new(34.0522, -18.2437, 15.0))
             .gps_quality(GPSQuality::DGPS)
             .age_dgps(Duration::from_secs_f64(2.5))
             .geoidal_separation(1.0)
@@ -169,7 +170,7 @@ mod test {
 
         assert_eq!(
             sentence,
-            "$GPGGA,0189.00,3403.1320000,N,11814.6220000,W,2,8,1.2,0.0,M,1.00,2,42*1D\r\n"
+            "$GPGGA,0189.00,3403.1320000,N,01814.6220000,W,2,8,1.2,0.0,M,1.00,2,42*1C\r\n"
         );
     }
 

From 305bef4385587419202bcf198edd27f97067f9f0 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 13:37:11 -0700
Subject: [PATCH 16/17] add docs

---
 swiftnav/src/nmea/checksum.rs | 10 ++++++++++
 swiftnav/src/nmea/gga.rs      | 13 ++++++++++++-
 swiftnav/src/nmea/mod.rs      | 14 ++++++++++++++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/swiftnav/src/nmea/checksum.rs b/swiftnav/src/nmea/checksum.rs
index ec8e64b..0925867 100644
--- a/swiftnav/src/nmea/checksum.rs
+++ b/swiftnav/src/nmea/checksum.rs
@@ -1,3 +1,13 @@
+// Copyright (c) 2025 Swift Navigation Inc.
+// Contact: Swift Navigation <dev@swiftnav.com>
+//
+// This source is subject to the license found in the file 'LICENSE' which must
+// be be distributed together with this source. All other rights reserved.
+//
+// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
+// EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
+
 fn u8_to_nibbles(byte: u8) -> (u8, u8) {
     // The high nibble is obtained by shifting the byte 4 bits to the right.
     // This discards the lower 4 bits and moves the upper 4 bits into the lower 4 bit positions.
diff --git a/swiftnav/src/nmea/gga.rs b/swiftnav/src/nmea/gga.rs
index 2945a44..9f88849 100644
--- a/swiftnav/src/nmea/gga.rs
+++ b/swiftnav/src/nmea/gga.rs
@@ -1,3 +1,13 @@
+// Copyright (c) 2025 Swift Navigation Inc.
+// Contact: Swift Navigation <dev@swiftnav.com>
+//
+// This source is subject to the license found in the file 'LICENSE' which must
+// be be distributed together with this source. All other rights reserved.
+//
+// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
+// EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
+
 use std::{
     fmt::{self},
     time::Duration,
@@ -51,7 +61,8 @@ impl fmt::Display for GPSQuality {
     }
 }
 
-/// Geographic coordinates including altitude, GPS solution quality, DGPS usage information.
+/// Global Positioning System Fix Data including time, position and fix related data for a GNSS
+/// receiver
 #[derive(Debug, PartialEq, Clone, Builder)]
 pub struct GGA {
     /// Time of fix in UTC.
diff --git a/swiftnav/src/nmea/mod.rs b/swiftnav/src/nmea/mod.rs
index de97cdc..e1b1173 100644
--- a/swiftnav/src/nmea/mod.rs
+++ b/swiftnav/src/nmea/mod.rs
@@ -1,3 +1,17 @@
+// Copyright (c) 2025 Swift Navigation Inc.
+// Contact: Swift Navigation <dev@swiftnav.com>
+//
+// This source is subject to the license found in the file 'LICENSE' which must
+// be be distributed together with this source. All other rights reserved.
+//
+// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
+// EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
+// WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
+
+//! This module contains National Marine Electronics Association (NMEA) related structures and
+//! formatting utilities. Notably, it contains (or eventually will contain) structures related to
+//! NMEA sentences and parsing/serialization of those sentences.
+
 mod checksum;
 mod gga;
 

From 2e125ab1ad371ecfa0c23b357daa03bb57981071 Mon Sep 17 00:00:00 2001
From: Theodore Zilist <14153237+tzilist@users.noreply.github.com>
Date: Mon, 27 Oct 2025 15:04:41 -0700
Subject: [PATCH 17/17] add source back in

---
 swiftnav/src/nmea/checksum.rs |  2 +-
 swiftnav/src/nmea/gga.rs      | 31 +++++++++++++++++++++++++------
 swiftnav/src/nmea/mod.rs      |  2 ++
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/swiftnav/src/nmea/checksum.rs b/swiftnav/src/nmea/checksum.rs
index 0925867..5595eba 100644
--- a/swiftnav/src/nmea/checksum.rs
+++ b/swiftnav/src/nmea/checksum.rs
@@ -36,7 +36,7 @@ pub fn calculate_checksum(sentence: &str) -> String {
     let mut checksum = 0;
 
     for (i, byte) in sentence.bytes().enumerate() {
-        // Skip the starting '$' and the '*' before the checksum
+        // Skip the starting '$'
         if i == 0 && byte == b'$' {
             continue;
         }
diff --git a/swiftnav/src/nmea/gga.rs b/swiftnav/src/nmea/gga.rs
index 9f88849..cd710c8 100644
--- a/swiftnav/src/nmea/gga.rs
+++ b/swiftnav/src/nmea/gga.rs
@@ -18,7 +18,7 @@ use chrono::{DateTime, Timelike, Utc};
 
 use crate::{
     coords::LLHDegrees,
-    nmea::{self},
+    nmea::{self, Source},
 };
 
 /// Quality of GPS solution
@@ -31,7 +31,7 @@ pub enum GPSQuality {
     SPS,
     /// Differential GPS, SPS Mode, fix valid
     DGPS,
-    /// GPS PPS (pulse per second), fix valid
+    /// GPS PPS (precise positioning service, military encrypted signals), fix valid
     PPS,
     /// RTK (real time kinematic). System used in RTK mode with fixed integers
     RTK,
@@ -61,17 +61,28 @@ impl fmt::Display for GPSQuality {
     }
 }
 
+#[derive(thiserror::Error, Debug)]
+pub enum GGAParseError {
+    #[error("Invalid time format")]
+    InvalidTimeFormat,
+
+    #[error("Invalid or missing GPS quality")]
+    InvalidGPSQuality,
+}
+
 /// Global Positioning System Fix Data including time, position and fix related data for a GNSS
 /// receiver
 #[derive(Debug, PartialEq, Clone, Builder)]
 pub struct GGA {
+    #[builder(default)]
+    pub source: Source,
     /// Time of fix in UTC.
     #[builder(default = Utc::now())]
     pub time: DateTime<Utc>,
     /// Latitude, longitude and height in degrees.
     pub llh: LLHDegrees,
     /// Quality of GPS solution.
-    #[builder(default = GPSQuality::default())]
+    #[builder(default)]
     pub gps_quality: GPSQuality,
     /// Sattelites in use
     pub sat_in_use: Option<u8>,
@@ -86,10 +97,18 @@ pub struct GGA {
 }
 
 impl GGA {
-    // converts the GGA struct into an NMEA sentence
-    // http://lefebure.com/articles/nmea-gga/
+    /// converts the GGA struct into an NMEA sentence
+    ///
+    /// <https://gpsd.gitlab.io/gpsd/NMEA.html#_gga_global_positioning_system_fix_data>
+    ///
+    /// ```text
+    ///        1         2       3 4        5 6 7  8   9  10 |  12 13  14   15
+    ///        |         |       | |        | | |  |   |   | |   | |   |    |
+    /// $--GGA,hhmmss.ss,ddmm.mm,a,ddmm.mm,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx*hh<CR><LF>
+    /// ```
     #[must_use]
     pub fn to_sentence(&self) -> String {
+        let talker_id = self.source.to_nmea_talker_id();
         // NOTE(ted): We are formatting here a bit strange because for some ungodly reason,
         // chrono chose not to allow for abitrary fractional seconds precision when formatting
         // Construct timestamp in HHMMSS.SS format
@@ -129,7 +148,7 @@ impl GGA {
             .map_or(String::new(), |id| id.to_string());
 
         let sentence = format!(
-            "GPGGA,{timestamp},{lat_deg:02}{lat_mins:010.7},{lat_hemisphere},{lon_deg:\
+            "{talker_id}GGA,{timestamp},{lat_deg:02}{lat_mins:010.7},{lat_hemisphere},{lon_deg:\
              03}{lon_mins:010.7},{lon_hemisphere},{gps_quality},{sat_in_use},{hdop},{height:.6},M,\
              {geoidal_separation},{age_dgps:.1},{reference_station_id}",
         );
diff --git a/swiftnav/src/nmea/mod.rs b/swiftnav/src/nmea/mod.rs
index e1b1173..dfdce89 100644
--- a/swiftnav/src/nmea/mod.rs
+++ b/swiftnav/src/nmea/mod.rs
@@ -14,6 +14,8 @@
 
 mod checksum;
 mod gga;
+mod source;
 
 pub use checksum::*;
 pub use gga::*;
+pub use source::*;