1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
|
import re
from django.contrib.gis import gdal
from django.utils import six
from django.utils.encoding import python_2_unicode_compatible
@python_2_unicode_compatible
class SpatialRefSysMixin(object):
"""
The SpatialRefSysMixin is a class used by the database-dependent
SpatialRefSys objects to reduce redundant 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>[^ ,\]]+)', re.DOTALL)
@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 as e:
msg = e
try:
self._srs = gdal.SpatialReference(self.proj4text)
return self.srs
except Exception as e:
msg = e
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):
"""
Return a tuple of (unit_value, unit_name) for the given WKT without
using any of the database fields.
"""
if gdal.HAS_GDAL:
return gdal.SpatialReference(wkt).units
else:
m = cls.units_regex.match(wkt)
return float(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 __str__(self):
"""
Returns the string representation. If GDAL is installed,
it will be 'pretty' OGC WKT.
"""
try:
return six.text_type(self.srs)
except Exception:
return six.text_type(self.wkt)
|
