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283 lines
10 KiB
283 lines
10 KiB
""" |
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Imports the SpatialRefSys and GeometryColumns models dependent on the |
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spatial database backend. |
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""" |
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import re |
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from django.conf import settings |
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|
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# Checking for the presence of GDAL (needed for the SpatialReference object) |
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from django.contrib.gis.gdal import HAS_GDAL, PYTHON23 |
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if HAS_GDAL: |
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from django.contrib.gis.gdal import SpatialReference |
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|
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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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|
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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, or 'b' |
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# 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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|
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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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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 HAS_GDAL: |
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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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|
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# Trying to get from WKT first. |
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try: |
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self._srs = 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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|
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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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srs = property(srs) |
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|
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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 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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ellipsoid = property(ellipsoid) |
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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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name = property(name) |
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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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spheroid = property(spheroid) |
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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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datum = property(datum) |
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def projected(self): |
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"Is this Spatial Reference projected?" |
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if 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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projected = property(projected) |
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def local(self): |
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"Is this Spatial Reference local?" |
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if 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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local = property(local) |
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def geographic(self): |
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"Is this Spatial Reference geographic?" |
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if 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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geographic = property(geographic) |
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def linear_name(self): |
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"Returns the linear units name." |
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if 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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linear_name = property(linear_name) |
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def linear_units(self): |
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"Returns the linear units." |
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if 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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linear_units = property(linear_units) |
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def angular_name(self): |
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"Returns the name of the angular units." |
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if 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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angular_name = property(angular_name) |
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def angular_units(self): |
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"Returns the angular units." |
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if 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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angular_units = property(angular_units) |
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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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units = property(units) |
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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 HAS_GDAL: |
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return 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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get_units = classmethod(get_units) |
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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 HAS_GDAL: |
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srs = 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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get_spheroid = classmethod(get_spheroid) |
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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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# The SpatialRefSys and GeometryColumns models |
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_srid_info = True |
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if not PYTHON23 and settings.DATABASE_ENGINE == 'postgresql_psycopg2': |
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# Because the PostGIS version is checked when initializing the spatial |
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# backend a `ProgrammingError` will be raised if the PostGIS tables |
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# and functions are not installed. We catch here so it won't be raised when |
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# running the Django test suite. `ImportError` is also possible if no ctypes. |
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try: |
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from django.contrib.gis.db.backend.postgis.models import GeometryColumns, SpatialRefSys |
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except: |
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_srid_info = False |
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elif not PYTHON23 and settings.DATABASE_ENGINE == 'oracle': |
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# Same thing as above, except the GEOS library is attempted to be loaded for |
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# `BaseSpatialBackend`, and an exception will be raised during the |
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# Django test suite if it doesn't exist. |
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try: |
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from django.contrib.gis.db.backend.oracle.models import GeometryColumns, SpatialRefSys |
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except: |
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_srid_info = False |
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else: |
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_srid_info = False |
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if _srid_info: |
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def get_srid_info(srid): |
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""" |
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Returns the units, unit name, and spheroid WKT associated with the |
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given SRID from the `spatial_ref_sys` (or equivalent) spatial database |
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table. We use a database cursor to execute the query because this |
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function is used when it is not possible to use the ORM (for example, |
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during field initialization). |
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""" |
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# SRID=-1 is a common convention for indicating the geometry has no |
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# spatial reference information associated with it. Thus, we will |
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# return all None values without raising an exception. |
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if srid == -1: return None, None, None |
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# Getting the spatial reference WKT associated with the SRID from the |
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# `spatial_ref_sys` (or equivalent) spatial database table. This query |
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# cannot be executed using the ORM because this information is needed |
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# when the ORM cannot be used (e.g., during the initialization of |
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# `GeometryField`). |
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from django.db import connection |
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cur = connection.cursor() |
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qn = connection.ops.quote_name |
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stmt = 'SELECT %(table)s.%(wkt_col)s FROM %(table)s WHERE (%(table)s.%(srid_col)s = %(srid)s)' |
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stmt = stmt % {'table' : qn(SpatialRefSys._meta.db_table), |
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'wkt_col' : qn(SpatialRefSys.wkt_col()), |
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'srid_col' : qn('srid'), |
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'srid' : srid, |
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} |
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cur.execute(stmt) |
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# Fetching the WKT from the cursor; if the query failed raise an Exception. |
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fetched = cur.fetchone() |
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if not fetched: |
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raise ValueError('Failed to find spatial reference entry in "%s" corresponding to SRID=%s.' % |
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(SpatialRefSys._meta.db_table, srid)) |
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srs_wkt = fetched[0] |
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# Getting metadata associated with the spatial reference system identifier. |
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# Specifically, getting the unit information and spheroid information |
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# (both required for distance queries). |
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unit, unit_name = SpatialRefSys.get_units(srs_wkt) |
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spheroid = SpatialRefSys.get_spheroid(srs_wkt) |
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return unit, unit_name, spheroid |
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else: |
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def get_srid_info(srid): |
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""" |
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Dummy routine for the backends that do not have the OGC required |
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spatial metadata tables (like MySQL). |
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""" |
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return None, None, None |
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