Merge pull request #2633 from simonrp84/insaT_upd

Update INSAT-3D reader to get satellite location from file
pytroll · Nov 28, 2023 · 28aba2f · 28aba2f
2 parents 72e2a71 + 79585f1
commit 28aba2f
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Showing 2 changed files with 13 additions and 3 deletions.
diff --git a/satpy/readers/insat3d_img_l1b_h5.py b/satpy/readers/insat3d_img_l1b_h5.py
@@ -173,7 +173,12 @@ def get_area_def(self, ds_id):
         lines = shape[-2]
         cols = shape[-1]
 
-        fov = self.datatree.attrs["Field_of_View(degrees)"]
+        # From empirical analysis, hardcoding the view of view to 18 degrees
+        # produces better geolocation results.
+        # Uncommenting the line below will use the fov from the file instead,
+        # this line is kept for reference.
+        #fov = self.datatree.attrs["Field_of_View(degrees)"]
+        fov = 18
         cfac = 2 ** 16 / (fov / cols)
         lfac = 2 ** 16 / (fov / lines)
 
@@ -182,6 +187,8 @@ def get_area_def(self, ds_id):
         a = 6378137.0
         b = 6356752.314245
 
+        subsatellite_longitude = self.datatree.attrs["Nominal_Central_Point_Coordinates(degrees)_Latitude_Longitude"][1]
+
         pdict = {
             "cfac": cfac,
             "lfac": lfac,
@@ -193,7 +200,7 @@ def get_area_def(self, ds_id):
             "a": a,
             "b": b,
             "h": h,
-            "ssp_lon": 82.0,
+            "ssp_lon": subsatellite_longitude,
             "a_name": "insat3d82",
             "a_desc": "insat3d82",
             "p_id": "geosmsg"

diff --git a/satpy/tests/reader_tests/test_insat3d_img_l1b_h5.py b/satpy/tests/reader_tests/test_insat3d_img_l1b_h5.py
@@ -74,14 +74,15 @@
 
 start_time = datetime(2009, 6, 9, 9, 0)
 end_time = datetime(2009, 6, 9, 9, 30)
+subsatellite_longitude = 82
 
 time_pattern = "%d-%b-%YT%H:%M:%S"
 
 global_attrs = {"Observed_Altitude(km)": 35778.490219,
                 "Field_of_View(degrees)": 17.973925,
                 "Acquisition_Start_Time": start_time.strftime(time_pattern),
                 "Acquisition_End_Time": end_time.strftime(time_pattern),
-                "Nominal_Central_Point_Coordinates(degrees)_Latitude_Longitude": [0.0, 82.0],
+                "Nominal_Central_Point_Coordinates(degrees)_Latitude_Longitude": [0.0, subsatellite_longitude],
                 "Nominal_Altitude(km)": 36000.0,
                 }
 
@@ -243,6 +244,7 @@ def test_insat3d_has_orbital_parameters(insat_filehandler):
 
     assert "orbital_parameters" in darr.attrs
     assert "satellite_nominal_longitude" in darr.attrs["orbital_parameters"]
+    assert darr.attrs["orbital_parameters"]["satellite_nominal_longitude"] == subsatellite_longitude
     assert "satellite_nominal_latitude" in darr.attrs["orbital_parameters"]
     assert "satellite_nominal_altitude" in darr.attrs["orbital_parameters"]
     assert "satellite_actual_altitude" in darr.attrs["orbital_parameters"]
@@ -276,6 +278,7 @@ def test_filehandler_returns_area(insat_filehandler):
     ds_id = make_dataid(name="MIR", resolution=4000, calibration="brightness_temperature")
     area_def = fh.get_area_def(ds_id)
     lons, lats = area_def.get_lonlats(chunks=1000)
+    assert "+lon_0=" + str(subsatellite_longitude) in area_def.crs.to_proj4()
 
 
 def test_filehandler_has_start_and_end_time(insat_filehandler):