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LSST Data Management Base Package
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equatSkyMap.py
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2# LSST Data Management System
3# Copyright 2008, 2009, 2010 LSST Corporation.
4#
5# This product includes software developed by the
6# LSST Project (http://www.lsst.org/).
7#
8# This program is free software: you can redistribute it and/or modify
9# it under the terms of the GNU General Public License as published by
10# the Free Software Foundation, either version 3 of the License, or
11# (at your option) any later version.
12#
13# This program is distributed in the hope that it will be useful,
14# but WITHOUT ANY WARRANTY; without even the implied warranty of
15# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16# GNU General Public License for more details.
17#
18# You should have received a copy of the LSST License Statement and
19# the GNU General Public License along with this program. If not,
20# see <http://www.lsstcorp.org/LegalNotices/>.
21#
22
23__all__ = ['EquatSkyMapConfig', 'EquatSkyMap']
24
25import struct
26
27import lsst.pex.config as pexConfig
28import lsst.geom as geom
29from .baseSkyMap import BaseSkyMap
30from .tractInfo import TractInfo
31
32
33class EquatSkyMapConfig(BaseSkyMap.ConfigClass):
34 numTracts = pexConfig.Field(
35 doc="number of tracts; warning: TAN projection requires at least 3",
36 dtype=int,
37 default=4,
38 )
39 decRange = pexConfig.ListField(
40 doc="range of declination (deg)",
41 dtype=float,
42 length=2,
43 default=(-1.25, 1.25),
44 )
45
46 def setDefaults(self):
47 self.projection = "CEA"
48
49
51 """Equatorial sky map pixelization, e.g. for SDSS stripe 82 image data.
52
53 EquatSkyMap represents an equatorial band of sky divided along declination
54 into overlapping tracts.
55
56 Parameters
57 ----------
58 config : `lsst.skymap.BaseSkyMapConfig` (optional)
59 The configuration for this SkyMap; if None use the default config.
60 """
61 ConfigClass = EquatSkyMapConfig
62 _version = (1, 0) # for pickle
63
64 def __init__(self, config=None):
65 BaseSkyMap.__init__(self, config)
66
67 decRange = tuple(geom.Angle(dr, geom.degrees) for dr in self.config.decRange)
68 midDec = (decRange[0] + decRange[1]) / 2.0
69 tractWidthRA = geom.Angle(360.0 / self.config.numTracts, geom.degrees)
70 tractOverlap = geom.Angle(self.config.tractOverlap, geom.degrees)
71
72 for id in range(self.config.numTracts):
73 begRA = tractWidthRA * id
74 endRA = begRA + tractWidthRA
75 vertexCoordList = (
76 geom.SpherePoint(begRA, decRange[0]),
77 geom.SpherePoint(endRA, decRange[0]),
78 geom.SpherePoint(endRA, decRange[1]),
79 geom.SpherePoint(begRA, decRange[1]),
80 )
81
82 midRA = begRA + tractWidthRA / 2.0
83 ctrCoord = geom.SpherePoint(midRA, midDec)
84
85 # CRVal must have Dec=0 for symmetry about the equator
86 crValCoord = geom.SpherePoint(midRA, geom.Angle(0.0))
87
88 # Make initial WCS; don't worry about crPixPos because TractInfo
89 # will shift it as required.
90 wcs = self._wcsFactory.makeWcs(crPixPos=geom.Point2D(0, 0), crValCoord=crValCoord)
91
92 self._tractInfoList.append(TractInfo(
93 id=id,
94 tractBuilder=self._tractBuilder,
95 ctrCoord=ctrCoord,
96 vertexCoordList=vertexCoordList,
97 tractOverlap=tractOverlap,
98 wcs=wcs,
99 ))
100
101 def __getstate__(self):
102 """Support pickle.
103
104 Returns
105 -------
106 stateDict : `dict`
107 a dict containing:
108 - version: a pair of ints
109 - config: the config
110 """
111 return dict(
112 version=self._version,
113 config=self.config,
114 )
115
116 def __setstate__(self, stateDict):
117 """Support unpickle
118
119 Parameters
120 ----------
121 stateDict : `dict`
122 a dict containing:
123 - version: a pair of ints
124 - config: the config
125 """
126 version = stateDict["version"]
127 if version >= (2, 0):
128 raise RuntimeError("Version = %s >= (2,0); cannot unpickle" % (version,))
129 self.__init____init__(stateDict["config"])
130
131 def getVersion(self):
132 """Return version (e.g. for pickle).
133
134 Returns
135 -------
136 result : `tuple` of `int`
137 Version as a pair of integers.
138 """
139 return self._version
140
141 def updateSha1(self, sha1):
142 """Add subclass-specific state or configuration options to the SHA1."""
143 sha1.update(struct.pack("<i2d", self.config.numTracts, *self.config.decRange))
A class representing an angle.
Definition Angle.h:128
Point in an unspecified spherical coordinate system.
Definition SpherePoint.h:57