Source code for

"""**Class projection**

from osgeo import osr

# The projection string depends on the gdal version
DEFAULT_PROJECTION = '+proj=longlat +datum=WGS84 +no_defs'

[docs]def proj4_to_dict(P): """Helper to turn a proj4 string into a dictionary for ease of comparison See issue #304 Args: P: proj4 string, such as +proj=longlat +ellps=WGS84 +no_defs Returns dictionary of individual elements, e.g. {'+proj': 'longlat', '+ellps': 'WGS84', '+no_defs': ''} """ D = {} for e in P.split(): fields = e.strip().split('=') if len(fields) > 1: val = fields[1] else: val = '' D[fields[0]] = val return D
[docs]class Projection: """Represents projections associated with layers """ def __init__(self, p): """Constructor for Projection. Args: * p: Projection information. Any of the GDAL formats are OK including WKT, proj4, ESRI, XML It can also be an instance of Projection. """ if p is None: # msg = 'Requested projection is None' # raise TypeError(msg) p = DEFAULT_PROJECTION # Clean input string. This will also work when p is of class # Projection by virtue of its __repr__() p = str(p).strip() # Create OSR spatial reference object srs = self.spatial_reference = osr.SpatialReference() # Try importing input_OK = False for import_func in [srs.ImportFromProj4, srs.ImportFromWkt, srs.ImportFromEPSG, srs.ImportFromESRI, # FIXME (Ole): This one emits the warning: # Warning 5: Failed parsing CoordSys: # 'Indonesia TM-3 zone 48.2' # srs.ImportFromMICoordSys, srs.ImportFromPCI, srs.ImportFromXML, srs.ImportFromUSGS, srs.ImportFromUrl]: try: res = import_func(p) except TypeError: # FIXME: NetCDF raster layer gives SRS error # Occasionally we get things like # File "/usr/lib/python2.7/dist-packages/osgeo/", # line 639, in ImportFromEPSG # return _osr.SpatialReference_ImportFromEPSG(self, *args) # TypeError: in method 'SpatialReference_ImportFromEPSG', # argument 2 of type 'int' # e.g. when using NetCDF multiband data. Why? pass if res == 0: input_OK = True break if not input_OK: msg = 'Spatial reference %s was not recognised' % p raise TypeError(msg) # Store some - FIXME this is only for backwards compat, remove. self.wkt = self.get_projection(proj4=False) self.proj4 = self.get_projection(proj4=True) def __repr__(self): return self.wkt
[docs] def get_projection(self, proj4=False): """Return projection Args: * proj4: If True, projection will be returned in proj4 format. If False (default) projection will be returned in WKT format Note: To compare projections, use the __eq__ method directly on the projection objects: E.g. self.projection == other.projection """ if proj4: p = self.spatial_reference.ExportToProj4() else: p = self.spatial_reference.ExportToWkt() return p.strip()
def __eq__(self, other): """Override '==' to allow comparison with other projection objecs """ try: other = Projection(other) except Exception, e: msg = ('Argument to == must be a spatial reference or object' ' of class Projection. I got %s with error ' 'message: %s' % (str(other), e)) raise TypeError(msg) if self.spatial_reference.IsSame(other.spatial_reference): # OSR comparison checks out return True else: # We have seen cases where the native comparison didn't work # for projections that should be identical. See e.g. # # FIXME (Ole): Someone, please find out how to robustly compare # projections # For now we do a secondary check using the proj4 string: # Pull +proj and +ellips fields and compare # Attempt to compare strings like this. This is non trivial # as the proj4 format does not always have the same parameters # conf e.g. +towgs84 or +ellps vs +datum (tsk tsk): # +proj=longlat +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +no_defs # +proj=longlat +ellps=WGS84 +no_defs # # And even worse: # +proj=longlat +datum=WGS84 +no_defs # +proj=longlat +ellps=WGS84 +no_defs # Get proj4 representations P1 = self.get_projection(proj4=True) P2 = other.get_projection(proj4=True) if P1 == P2: # Direct comparison of proj4 strings match return True else: # Check key elements D1 = proj4_to_dict(P1) D2 = proj4_to_dict(P2) result = True for key in D1: # Only compare keys that appear in both (see above) if key in D2: if D1[key] != D2[key]: result = False break return result def __ne__(self, other): """Override '!=' to allow comparison with other projection objecs """ return not self == other