Field-navigation prototype: tactical-style map with live MGRS, GeoPDF/calibrated-PDF basemaps, drawing overlays exportable as GeoJSON, and fiduciary calibration for any PDF that lacks proper georeferencing. iOS (SwiftUI + MapKit) and Android (Kotlin + Compose + Google Maps) ship from one repository.
More screenshots
The basemap screenshot (£2) is the USGS San Francisco North 1:24,000 US Topo
quadrangle (public domain) rendered live over the satellite. Run
scripts/fetch_samples.sh to drop the same PDF into samples/ for testing.
- Live MGRS in a tactical-green monospace at the top, spaced as
56HLH 13225 37516. Header flips between Your Location (GPS fix) and Map Centre (when you pan away) automatically. - WGS84 lat/lon + elevation (metres above sea level) live at the crosshair, fetched from Open-Meteo's Copernicus DEM (≈30 m global resolution) on a 400 ms debounce so we don't hammer the network during a pan.
- NATO mils compass (6400 per circle). The N marker rotates with the map so it always points to true north; the 4-digit mils readout in the lower half stays static. Tap to snap back to north-up.
- Centre-pivot rotation — the default
MKMapViewrotation drags the centre around with your fingers. Ours overrides it so the map spins in place around the screen centre.
- Drop waypoints with kind (camp, water, observation point, drop zone, hazard) and elevation.
- Draw polylines, polygons, and points — tap successive points on the map, undo last vertex, finish to commit. In-progress shapes render dashed.
- Export everything as GeoJSON following the Mapbox simplestyle-spec (stroke / stroke-width / fill / fill-opacity / marker-color / marker-symbol with Maki icon names). Opens directly in geojson.io, GitHub gists, Mapbox, Felt, Leaflet, QGIS, ArcGIS, Google Earth.
- Import any GeoPDF via the Files app. The PDF replaces the satellite basemap and stays anchored to its true geographic bounds when you pan / zoom / rotate.
- LGIDict parser handles the OGC GeoPDF format used by ADF, AUSLIG, USGS,
and most government topo PDFs:
- Multi-entry LGIDicts (picks the one with
/Description (Layers)) - PDF-string-encoded reals (e.g.
(135.83)instead of135.83) - Projections: LL (geographic), UT (UTM), TC (Transverse Mercator routed through UTM when the central meridian matches a zone)
- Multi-entry LGIDicts (picks the one with
- Adobe Geospatial fallback for newer PDFs that use
/VP/Measure+/GPTSinstead of LGIDict. - Fiduciary calibration UI for any PDF without proper metadata — tap
3 known features on the PDF, enter their MGRS, and
AffineFittersolves a least-squares affine to re-derive bounds. Shows RMS residual in metres so you know how trustworthy the fit is.
- Sideload a
.mbtilesraster pyramid (e.g.gdal_translate+gdal2tiles.pyof any GeoPDF / raster) and the app serves it through a tile overlay with no network — the real offline-field path, and the ToS-compliant alternative to caching Apple/Google's own tiles. Import via ☰ → Import Offline Tiles; the bounds metadata frames the camera, and the Layers sheet lets you unload it. iOS + Android.
- Place name / address via
MKLocalSearch, biased toward the current camera area. - Full MGRS — type
56HLH 13225 37516, jump straight there. - Partial grid — type just 4 / 6 / 8 / 10 figures (e.g.
1885) and we resolve against your current GZD + 100km square prefix, then drop you at the centre of the implied square (1 km / 100 m / 10 m / 1 m precision respectively). - Crash-safe: regex pre-validates MGRS shape before calling NGA's parser
(which used to
fatalErroron partial input).
.
├── ios/ SwiftUI app, XcodeGen-driven
│ ├── project.yml → .xcodeproj generation
│ ├── TacticalMaps/ app source
│ └── Vendor/mgrs-ios/ vendored fork with a 4-line Snyder UTM patch
├── android/ Kotlin + Compose, Gradle
├── docs/
│ ├── ARCHITECTURE.md shared design notes
│ ├── PRIVACY_POLICY.md public privacy policy (host this)
│ ├── APPSTORE_CHECKLIST.md submission checklist
│ └── screenshots/ README hero images
├── scripts/
│ └── generate_icon.swift re-generate the 1024×1024 App Store icon
└── samples/ (intentionally empty in the public repo)
# 1. Tools (one-off)
brew install xcodegen
sudo xcode-select -s /Applications/Xcode.app/Contents/Developer
xcodebuild -runFirstLaunch
# 2. Generate the Xcode project
cd ios
xcodegen generate
# 3. Open
open TacticalMaps.xcodeprojFirst build resolves Swift packages (mgrs is vendored, but pure-Swift deps still download). Pick an iPhone simulator and press ▶.
Generate the App Store icon (if you tweak the design in
scripts/generate_icon.swift):
swift scripts/generate_icon.swift# 1. Tools (one-off)
brew install --cask android-studio android-commandlinetools
open -a "Android Studio" # Run the first-launch SDK wizard + create an AVD
# 2. Get a Google Maps API key
# https://developers.google.com/maps/documentation/android-sdk/get-api-key
# Enable "Maps SDK for Android" on the project. Restrict the key by
# Android package (com.tacticalmaps) + debug + release SHA-1.
# Add the key to android/local.properties (gitignored):
# MAPS_API_KEY=AIza…
# (Falls back to the MAPS_API_KEY env var if the property is unset.)
# 3. Open in Studio
open -a "Android Studio" androidWithout an API key the map will render as a grey grid + watermark, but every other UI element still works.
Pure-logic unit tests run on both platforms and gate CI:
# iOS — XCTest (affine fit, MGRS, GeoJSON geometry, MBTiles, map geometry, …)
cd ios && xcodegen generate
xcodebuild test -scheme TacticalMaps -destination 'platform=iOS Simulator,name=iPhone 16 Pro'
# Android — JVM unit tests (no emulator needed)
cd android && ./gradlew testDebugUnitTestCross-platform invariants (the affine solve, MGRS formatting, GeoJSON geometry)
are pinned by shared golden vectors in testdata/ that both
suites load, so the Swift and Kotlin ports can't silently drift.
The single most important architectural choice: all overlays (waypoints,
drawings, fiduciaries) are stored in WGS84. MGRS is presentation-only,
computed on the fly via NGA's mgrs-ios. This means swapping basemaps
(satellite ↔ GeoPDF ↔ calibrated PDF) never requires re-projecting overlays.
Full design + math in docs/ARCHITECTURE.md.
- Wave 2 projections — Lambert Conformal Conic (French IGN, Canadian NRCan, US state plane), arbitrary-central-meridian TM (UK OSGB36, NZ NZTM), non-WGS84 datum shifts.
- Per-PDF fiduciary library — the active calibrated PDF's fiduciaries +
affine already persist across launches (
PDFSessionStore). A keyed library so switching between several PDFs remembers each one's calibration is still TODO. - Datum shift — calibration now lets you flag the sheet's datum (WGS84 / GDA94 / GDA2020) and shifts fiduciaries to WGS84 via the ICSM Helmert; Lambert Conformal Conic + arbitrary-TM datum work remains (see Wave 2 above).
- Route logging — the iOS
UIBackgroundModes: [location]declaration is in place; logger UI + GPX export TBD. - iCloud sync for waypoints + drawings.
- Android feature parity — drawing, search, waypoints + APP-6 symbols, GeoPDF import & fiduciary calibration, GeoJSON import/export, and the offline MBTiles basemap are all wired on Android now. The main iOS-only item left is the live DEM elevation readout in the HUD.
The iOS build is App-Store-ready in terms of assets:
- 1024×1024 icon, launch screen, acknowledgements view all in place
- Privacy policy at
docs/PRIVACY_POLICY.md - Step-by-step submission checklist at
docs/APPSTORE_CHECKLIST.md
It has not been submitted yet — if you do, see the checklist for the Apple-side steps (Developer Program enrolment, name reservation, screenshots, TestFlight).
We collect nothing. No accounts, no telemetry, no third-party SDKs, no
advertising IDs. Only outbound HTTPS calls are to Apple's Maps service (basemap
tiles + search) and Open-Meteo (elevation). Full disclosure in
docs/PRIVACY_POLICY.md.
MIT — see LICENSE. Includes vendored NGA mgrs-ios (MIT)
with a small Snyder UTM patch for Xcode 26 compatibility.