Added some input validation.

Signed-off-by: Daniel Scheffler <danschef@gfz-potsdam.de>

sensormapgeo/transformer_3d.py

@@ -192,6 +192,9 @@ class SensorMapGeometryTransformer3D(object):
             raise ValueError(data.shape, 'Expected a sensor geometry data array with %d rows, %d columns and %d bands.'
                              % self.lons.shape)
 
+        if not tgt_prj and not area_definition:
+            raise ValueError(tgt_prj, 'Target projection must be given if area_definition is not given.')
+
         if tgt_coordgrid:
             tgt_res = _get_validated_tgt_res(tgt_coordgrid, tgt_res)