more correct handling of band dimension in CMI and L1b

still need better handling of multi-band possibility

goesr/l1b.py

@@ -269,6 +269,7 @@ class PugFile(object):
     or a multi-band NetCDF4 file and an offset in the band dimension
     """
     nc = None  # if we opened the file for you, it's here
+    _band_offset = None
     band = None  # band number
     central_wavelength = None  # um
     platform_id = None  # platform_ID as string
@@ -276,7 +277,7 @@ class PugFile(object):
     time_span = None  # (start,end) datetime pair
     timeline_id = None  # string, instrument mode
     bit_depth = None  # bit depth
-    shape_m = None  # nadir-meter dy,dx approximation
+    shape_m = None  # nadir-meter dy,dx approximation : FUTURE: deprecate this toward cell_size, too confusing vs .shape being whole array
     scene_id = None  # string, type of scene e.g. "Full Disk"
     resolution = None  # approximate nadir meters: 500, 1000, 2000, 4000
     display_time = None  # str form of timeline YYYY-mm-dd HH:MM
@@ -305,15 +306,17 @@ class PugFile(object):
         :param primary_var_name: radiance variable to convert to BT/Refl
         :param band_offset: typically 0, eventually nonzero for multi-band files
         """
+        # FUTURE: handle band dimension more effectively, including surveying metadata for multi-band files
         super(PugFile, self).__init__()
         if not isinstance(nc, nc4.Dataset):  # then we can open and retain the file for our use
             nc = nc4.Dataset(nc)
             self.nc = nc
         self.primary_var_name = primary_var_name
         primary_var = nc[primary_var_name]
+        self._band_offset = band_offset
         self.band = int(nc['band_id'][band_offset])  # FUTURE: this has a band dimension
         self.nav = nc_nav_values(nc, primary_var_name)
-        self.shape = primary_var.shape
+        self.shape = primary_var.shape[-2:]
         self.platform_id = nc.platform_ID
         self.instrument_type = nc.instrument_type
         self.instrument_name = "ABI" if "Himawari" not in self.instrument_type else "AHI"
@@ -591,14 +594,14 @@ class PugCmiTools(PugFile):
     def data(self):
         if None is self.nc:
             return None
-        return self.nc[self.primary_var_name][:, :].squeeze()
+        return self.nc[self.primary_var_name][self._band_offset, :, :].squeeze()
 
     @property
     def bt(self):
         if None is self.nc:
             return None
         if 'bt' == self.bt_or_refl:
-            return self.nc[self.primary_var_name][:,:].squeeze()
+            return self.nc[self.primary_var_name][self._band_offset,:,:].squeeze()
         LOG.warning('cannot request bt from non-emissive band')
         return None
 
@@ -607,7 +610,7 @@ class PugCmiTools(PugFile):
         if None is self.nc:
             return None
         if 'refl' == self.bt_or_refl:
-            return self.nc[self.primary_var_name][:,:].squeeze()
+            return self.nc[self.primary_var_name][self._band_offset, :,:].squeeze()
         LOG.warning('cannot request refl from non-reflectance band')
         return None