328 lines
10 KiB
Python
328 lines
10 KiB
Python
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"""
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Base/mixin classes for the spatial backend database operations and the
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`SpatialRefSys` model the backend.
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"""
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import re
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from django.conf import settings
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from django.contrib.gis import gdal
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class BaseSpatialOperations(object):
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"""
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This module holds the base `BaseSpatialBackend` object, which is
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instantiated by each spatial database backend with the features
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it has.
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"""
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distance_functions = {}
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geometry_functions = {}
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geometry_operators = {}
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geography_operators = {}
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geography_functions = {}
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gis_terms = {}
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# Quick booleans for the type of this spatial backend, and
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# an attribute for the spatial database version tuple (if applicable)
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postgis = False
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spatialite = False
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mysql = False
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oracle = False
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spatial_version = None
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# How the geometry column should be selected.
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select = None
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# Does the spatial database have a geography type?
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geography = False
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area = False
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centroid = False
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difference = False
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distance = False
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distance_sphere = False
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distance_spheroid = False
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envelope = False
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force_rhr = False
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mem_size = False
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bounding_circle = False
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num_geom = False
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num_points = False
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perimeter = False
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perimeter3d = False
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point_on_surface = False
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polygonize = False
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scale = False
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snap_to_grid = False
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sym_difference = False
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transform = False
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translate = False
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union = False
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# Aggregates
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collect = False
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extent = False
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extent3d = False
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make_line = False
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unionagg = False
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# Serialization
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geohash = False
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geojson = False
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gml = False
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kml = False
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svg = False
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# Constructors
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from_text = False
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from_wkb = False
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# Default conversion functions for aggregates; will be overridden if implemented
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# for the spatial backend.
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def convert_extent(self, box):
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raise NotImplementedError('Aggregate extent not implemented for this spatial backend.')
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def convert_extent3d(self, box):
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raise NotImplementedError('Aggregate 3D extent not implemented for this spatial backend.')
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def convert_geom(self, geom_val, geom_field):
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raise NotImplementedError('Aggregate method not implemented for this spatial backend.')
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# For quoting column values, rather than columns.
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def geo_quote_name(self, name):
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if isinstance(name, unicode):
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name = name.encode('ascii')
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return "'%s'" % name
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# GeometryField operations
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def geo_db_type(self, f):
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"""
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Returns the database column type for the geometry field on
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the spatial backend.
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"""
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raise NotImplementedError
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def get_distance(self, f, value, lookup_type):
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"""
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Returns the distance parameters for the given geometry field,
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lookup value, and lookup type.
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"""
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raise NotImplementedError('Distance operations not available on this spatial backend.')
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def get_geom_placeholder(self, f, value):
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"""
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Returns the placeholder for the given geometry field with the given
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value. Depending on the spatial backend, the placeholder may contain a
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stored procedure call to the transformation function of the spatial
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backend.
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"""
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raise NotImplementedError
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# Spatial SQL Construction
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def spatial_aggregate_sql(self, agg):
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raise NotImplementedError('Aggregate support not implemented for this spatial backend.')
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def spatial_lookup_sql(self, lvalue, lookup_type, value, field):
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raise NotImplmentedError
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class SpatialRefSysMixin(object):
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"""
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The SpatialRefSysMixin is a class used by the database-dependent
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SpatialRefSys objects to reduce redundnant code.
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"""
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# For pulling out the spheroid from the spatial reference string. This
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# regular expression is used only if the user does not have GDAL installed.
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# TODO: Flattening not used in all ellipsoids, could also be a minor axis,
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# or 'b' parameter.
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spheroid_regex = re.compile(r'.+SPHEROID\[\"(?P<name>.+)\",(?P<major>\d+(\.\d+)?),(?P<flattening>\d{3}\.\d+),')
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# For pulling out the units on platforms w/o GDAL installed.
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# TODO: Figure out how to pull out angular units of projected coordinate system and
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# fix for LOCAL_CS types. GDAL should be highly recommended for performing
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# distance queries.
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units_regex = re.compile(r'.+UNIT ?\["(?P<unit_name>[\w \'\(\)]+)", ?(?P<unit>[\d\.]+)(,AUTHORITY\["(?P<unit_auth_name>[\w \'\(\)]+)","(?P<unit_auth_val>\d+)"\])?\]([\w ]+)?(,AUTHORITY\["(?P<auth_name>[\w \'\(\)]+)","(?P<auth_val>\d+)"\])?\]$')
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@property
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def srs(self):
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"""
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Returns a GDAL SpatialReference object, if GDAL is installed.
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"""
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if gdal.HAS_GDAL:
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# TODO: Is caching really necessary here? Is complexity worth it?
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if hasattr(self, '_srs'):
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# Returning a clone of the cached SpatialReference object.
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return self._srs.clone()
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else:
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# Attempting to cache a SpatialReference object.
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# Trying to get from WKT first.
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try:
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self._srs = gdal.SpatialReference(self.wkt)
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return self.srs
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except Exception, msg:
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pass
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try:
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self._srs = gdal.SpatialReference(self.proj4text)
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return self.srs
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except Exception, msg:
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pass
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raise Exception('Could not get OSR SpatialReference from WKT: %s\nError:\n%s' % (self.wkt, msg))
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else:
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raise Exception('GDAL is not installed.')
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@property
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def ellipsoid(self):
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"""
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Returns a tuple of the ellipsoid parameters:
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(semimajor axis, semiminor axis, and inverse flattening).
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"""
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if gdal.HAS_GDAL:
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return self.srs.ellipsoid
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else:
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m = self.spheroid_regex.match(self.wkt)
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if m: return (float(m.group('major')), float(m.group('flattening')))
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else: return None
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@property
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def name(self):
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"Returns the projection name."
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return self.srs.name
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@property
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def spheroid(self):
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"Returns the spheroid name for this spatial reference."
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return self.srs['spheroid']
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@property
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def datum(self):
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"Returns the datum for this spatial reference."
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return self.srs['datum']
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@property
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def projected(self):
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"Is this Spatial Reference projected?"
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if gdal.HAS_GDAL:
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return self.srs.projected
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else:
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return self.wkt.startswith('PROJCS')
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@property
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def local(self):
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"Is this Spatial Reference local?"
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if gdal.HAS_GDAL:
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return self.srs.local
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else:
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return self.wkt.startswith('LOCAL_CS')
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@property
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def geographic(self):
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"Is this Spatial Reference geographic?"
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if gdal.HAS_GDAL:
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return self.srs.geographic
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else:
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return self.wkt.startswith('GEOGCS')
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@property
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def linear_name(self):
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"Returns the linear units name."
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if gdal.HAS_GDAL:
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return self.srs.linear_name
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elif self.geographic:
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return None
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else:
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m = self.units_regex.match(self.wkt)
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return m.group('unit_name')
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@property
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def linear_units(self):
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"Returns the linear units."
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if gdal.HAS_GDAL:
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return self.srs.linear_units
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elif self.geographic:
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return None
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else:
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m = self.units_regex.match(self.wkt)
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return m.group('unit')
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@property
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def angular_name(self):
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"Returns the name of the angular units."
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if gdal.HAS_GDAL:
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return self.srs.angular_name
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elif self.projected:
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return None
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else:
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m = self.units_regex.match(self.wkt)
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return m.group('unit_name')
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@property
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def angular_units(self):
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"Returns the angular units."
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if gdal.HAS_GDAL:
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return self.srs.angular_units
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elif self.projected:
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return None
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else:
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m = self.units_regex.match(self.wkt)
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return m.group('unit')
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@property
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def units(self):
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"Returns a tuple of the units and the name."
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if self.projected or self.local:
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return (self.linear_units, self.linear_name)
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elif self.geographic:
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return (self.angular_units, self.angular_name)
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else:
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return (None, None)
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@classmethod
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def get_units(cls, wkt):
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"""
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Class method used by GeometryField on initialization to
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retrive the units on the given WKT, without having to use
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any of the database fields.
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"""
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if gdal.HAS_GDAL:
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return gdal.SpatialReference(wkt).units
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else:
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m = cls.units_regex.match(wkt)
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return m.group('unit'), m.group('unit_name')
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@classmethod
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def get_spheroid(cls, wkt, string=True):
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"""
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Class method used by GeometryField on initialization to
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retrieve the `SPHEROID[..]` parameters from the given WKT.
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"""
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if gdal.HAS_GDAL:
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srs = gdal.SpatialReference(wkt)
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sphere_params = srs.ellipsoid
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sphere_name = srs['spheroid']
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else:
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m = cls.spheroid_regex.match(wkt)
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if m:
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sphere_params = (float(m.group('major')), float(m.group('flattening')))
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sphere_name = m.group('name')
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else:
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return None
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if not string:
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return sphere_name, sphere_params
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else:
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# `string` parameter used to place in format acceptable by PostGIS
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if len(sphere_params) == 3:
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radius, flattening = sphere_params[0], sphere_params[2]
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else:
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radius, flattening = sphere_params
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return 'SPHEROID["%s",%s,%s]' % (sphere_name, radius, flattening)
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def __unicode__(self):
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"""
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Returns the string representation. If GDAL is installed,
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it will be 'pretty' OGC WKT.
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"""
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try:
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return unicode(self.srs)
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except:
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return unicode(self.wkt)
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