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