Merge pull request #1262 from ameraner/add_RSS_HRV_navigation

Fix handling of HRV channel navigation for RSS data in seviri_l1b_native reader

satpy/readers/seviri_l1b_native.py

@@ -47,7 +47,6 @@
                                                  native_trailer)
 from satpy.readers._geos_area import get_area_definition
 
-
 logger = logging.getLogger('native_msg')
 
 
@@ -59,7 +58,7 @@ class NativeMSGFileHandler(BaseFileHandler, SEVIRICalibrationHandler):
     kwargs = {"calib_mode": "gsics",}
     """
 
-    def __init__(self, filename, filename_info, filetype_info,  calib_mode='nominal'):
+    def __init__(self, filename, filename_info, filetype_info, calib_mode='nominal'):
         """Initialize the reader."""
         super(NativeMSGFileHandler, self).__init__(filename,
                                                    filename_info,
@@ -146,7 +145,6 @@ def get_lrec(cols):
     def _get_memmap(self):
         """Get the memory map for the SEVIRI data."""
         with open(self.filename) as fp:
-
             data_dtype = self._get_data_dtype()
             hdr_size = native_header.itemsize
 
@@ -174,11 +172,11 @@ def _read_header(self):
         self.mda['platform_name'] = "Meteosat-" + SATNUM[self.platform_id]
 
         equator_radius = data15hd['GeometricProcessing'][
-            'EarthModel']['EquatorialRadius'] * 1000.
+                             'EarthModel']['EquatorialRadius'] * 1000.
         north_polar_radius = data15hd[
-            'GeometricProcessing']['EarthModel']['NorthPolarRadius'] * 1000.
+                                 'GeometricProcessing']['EarthModel']['NorthPolarRadius'] * 1000.
         south_polar_radius = data15hd[
-            'GeometricProcessing']['EarthModel']['SouthPolarRadius'] * 1000.
+                                 'GeometricProcessing']['EarthModel']['SouthPolarRadius'] * 1000.
         polar_radius = (north_polar_radius + south_polar_radius) * 0.5
         ssp_lon = data15hd['ImageDescription'][
             'ProjectionDescription']['LongitudeOfSSP']
@@ -239,7 +237,6 @@ def _read_trailer(self):
                      self.mda['number_of_lines'])
 
         with open(self.filename) as fp:
-
             fp.seek(hdr_size + data_size)
             data = np.fromfile(fp, dtype=native_trailer, count=1)
 
@@ -349,29 +346,18 @@ def get_area_extent(self, dataset_id):
             )
             raise NotImplementedError(msg)
 
-        # When dealing with HRV channel and full disk, area extent is
-        # in two pieces
-        if (dataset_id.name == 'HRV') and self.mda['is_full_disk']:
+        # check if data is in Rapid Scanning Service mode (RSS)
+        is_rapid_scan = self.trailer['15TRAILER']['ImageProductionStats']['ActualScanningSummary']['ReducedScan']
+
+        # The HRV channel in full disk mode comes in two separate areas, and each area has its own area extent stored
+        # in the trailer.
+        # In Rapid Scanning mode, only the "Lower" area (typically over Europe) is acquired and included in the files.
+        if (dataset_id.name == 'HRV') and (self.mda['is_full_disk'] or is_rapid_scan):
 
             # get actual navigation parameters from trailer data
             data15tr = self.trailer['15TRAILER']
             HRV_bounds = data15tr['ImageProductionStats']['ActualL15CoverageHRV']
 
-            # upper window
-            upper_north_line = HRV_bounds['UpperNorthLineActual']
-            upper_west_column = HRV_bounds['UpperWestColumnActual']
-            upper_south_line = HRV_bounds['UpperSouthLineActual']
-            upper_east_column = HRV_bounds['UpperEastColumnActual']
-
-            upper_area_extent = self._calculate_area_extent(
-                center_point, upper_north_line, upper_east_column,
-                upper_south_line, upper_west_column, we_offset,
-                ns_offset, column_step, line_step
-            )
-
-            upper_nlines = upper_north_line - upper_south_line + 1
-            upper_ncols = upper_west_column - upper_east_column + 1
-
             # lower window
             lower_north_line = HRV_bounds['LowerNorthLineActual']
             lower_west_column = HRV_bounds['LowerWestColumnActual']
@@ -384,14 +370,31 @@ def get_area_extent(self, dataset_id):
                 ns_offset, column_step, line_step
             )
 
+            if is_rapid_scan:
+                return lower_area_extent
+
             lower_nlines = lower_north_line - lower_south_line + 1
             lower_ncols = lower_west_column - lower_east_column + 1
 
+            # upper window
+            upper_north_line = HRV_bounds['UpperNorthLineActual']
+            upper_west_column = HRV_bounds['UpperWestColumnActual']
+            upper_south_line = HRV_bounds['UpperSouthLineActual']
+            upper_east_column = HRV_bounds['UpperEastColumnActual']
+
+            upper_area_extent = self._calculate_area_extent(
+                center_point, upper_north_line, upper_east_column,
+                upper_south_line, upper_west_column, we_offset,
+                ns_offset, column_step, line_step
+            )
+
+            upper_nlines = upper_north_line - upper_south_line + 1
+            upper_ncols = upper_west_column - upper_east_column + 1
+
             return [upper_area_extent, lower_area_extent, upper_nlines, upper_ncols, lower_nlines, lower_ncols]
 
-        # Otherwise area extent is in one piece, corner points are
-        # the same as for VISIR channels, HRV channel is having
-        # three times the amount of columns and rows
+        # If the data was ordered in a defined ROI, the area extent is in one piece, the corner points are
+        # the same as for VISIR channels, and the HRV channel is having three times the amount of columns and rows.
         else:
 
             north = coeff * int(sec15hd['NorthLineSelectedRectangle']['Value'])