gis: added models for the PostGIS/OGC geometric tables 'spatial_ref_sys' and

'geometry_columns'.


git-svn-id: http://code.djangoproject.com/svn/django/branches/gis@4997 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/contrib/gis/models.py

@@ -0,0 +1,67 @@
+import re
+from django.db import models
+
+"""
+  Models for the PostGIS/OGC database tables.
+"""
+
+# For pulling out the spheroid from the spatial reference string.
+#  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 projected coordinate system units.  Python regexs are greedy
+#  by default, so this should get the units of the projection instead (PROJCS)
+#  of the units for the geographic coordinate system (GEOGCS).
+unit_regex = re.compile(r'^PROJCS.+UNIT\[\"(?P<units>[a-z]+)\", ?(?P<conversion>[0-9\.]+), ?(AUTHORITY\[\"(?P<authority>[a-z0-9 \.]+)\",[ ]?\"(?P<code>\d+)\"\])?', re.I)
+
+# This is the global 'geometry_columns' from PostGIS.
+#   See PostGIS Documentation at Ch. 4.2.2
+class GeometryColumns(models.Model):
+    f_table_catalog = models.CharField(maxlength=256)
+    f_table_schema = models.CharField(maxlength=256)
+    f_table_name = models.CharField(maxlength=256)
+    f_geometry_column = models.CharField(maxlength=256)
+    coord_dimension = models.IntegerField()
+    srid = models.IntegerField()
+    type = models.CharField(maxlength=30)
+
+    class Meta:
+        db_table = 'geometry_columns'
+
+# This is the global 'spatial_ref_sys' table from PostGIS.
+#   See PostGIS Documentation at Ch. 4.2.1
+class SpatialRefSys(models.Model):
+    srid = models.IntegerField(primary_key=True)
+    auth_name = models.CharField(maxlength=256)
+    auth_srid = models.IntegerField()
+    srtext = models.CharField(maxlength=2048)
+    proj4text = models.CharField(maxlength=2048)
+
+    class Meta:
+        db_table = 'spatial_ref_sys'
+                                                                                
+    @property
+    def spheroid(self):
+        "Pulls out the spheroid from the srtext."
+        m = spheroid_regex.match(self.srtext)
+        if m:
+            return (m.group('name'), float(m.group('major')), float(m.group('flattening')))
+        else:
+            return None
+
+    @property
+    def projected_units(self):
+        "If the spatial reference system is projected, get the units or return None."
+        m = unit_regex.match(self.srtext)
+        if m:
+            if m.group('authority'):
+                authority = (m.group('authority'), int(m.group('code')))
+            else:
+                authority = None
+            return (m.group('units'), float(m.group('conversion')), authority)
+        else:
+            return None
+
+    def __str__(self):
+        return "%d - %s " % (self.srid, self.auth_name)