LSSTApplications  20.0.0
LSSTDataManagementBasePackage
healpixSkyMap.py
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22 
23 __all__ = ['HealpixSkyMapConfig', 'HealpixSkyMap']
24 
25 import struct
26 import numpy
27 
28 # We want to register the HealpixSkyMap, but want "healpy" to be an
29 # optional dependency. However, the HealpixSkyMap requires the use
30 # of healpy. Therefore, we'll only raise an exception on the healpy
31 # import when it comes time to using it.
32 try:
33  import healpy
34 except Exception as e:
35  class DummyHealpy:
36  """An object which blows up when we try to read it"""
37 
38  def __getattr__(self, name, e=e):
39  raise RuntimeError("Was unable to import healpy: %s" % e)
40  healpy = DummyHealpy()
41 
42 from lsst.pex.config import Field
43 import lsst.geom as geom
44 from .cachingSkyMap import CachingSkyMap
45 from .tractInfo import TractInfo
46 
47 
48 def angToCoord(thetaphi):
49  """Convert healpy's ang to an lsst.geom.SpherePoint
50 
51  The ang is provided as a single object, thetaphi, so the output
52  of healpy functions can be directed to this function without
53  additional translation.
54  """
55  return geom.SpherePoint(float(thetaphi[1]), float(thetaphi[0] - 0.5*numpy.pi), geom.radians)
56 
57 
58 def coordToAng(coord):
59  """Convert an lsst.geom.SpherePoint to a healpy ang (theta, phi)
60 
61  The Healpix convention is that 0 <= theta <= pi, 0 <= phi < 2pi.
62  """
63  return (coord.getLatitude().asRadians() + 0.5*numpy.pi, coord.getLongitude().asRadians())
64 
65 
67  """Tract for the HealpixSkyMap"""
68 
69  def __init__(self, nSide, ident, nest, patchInnerDimensions, patchBorder, ctrCoord, tractOverlap, wcs):
70  """Set vertices from nside, ident, nest"""
71  theta, phi = healpy.vec2ang(numpy.transpose(healpy.boundaries(nSide, ident, nest=nest)))
72  vertexList = [angToCoord(thetaphi) for thetaphi in zip(theta, phi)]
73  super(HealpixTractInfo, self).__init__(ident, patchInnerDimensions, patchBorder, ctrCoord,
74  vertexList, tractOverlap, wcs)
75 
76 
77 class HealpixSkyMapConfig(CachingSkyMap.ConfigClass):
78  """Configuration for the HealpixSkyMap"""
79  log2NSide = Field(dtype=int, default=0, doc="Number of sides, expressed in powers of 2")
80  nest = Field(dtype=bool, default=False, doc="Use NEST ordering instead of RING?")
81 
82  def setDefaults(self):
83  self.rotation = 45 # HEALPixels are oriented at 45 degrees
84 
85 
87  """HEALPix-based sky map pixelization.
88 
89  We put a Tract at the position of each HEALPixel.
90 
91 
92  Parameters
93  ----------
94  config : `lsst.skymap.BaseSkyMapConfig`
95  The configuration for this SkyMap.
96  version : `int` or `tuple` of `int` (optional)
97  Software version of this class, to retain compatibility with old
98  instances.
99  """
100  ConfigClass = HealpixSkyMapConfig
101  _version = (1, 0) # for pickle
102  numAngles = 4 # Number of angles for vertices
103 
104  def __init__(self, config, version=0):
105  self._nside = 1 << config.log2NSide
106  numTracts = healpy.nside2npix(self._nside)
107  super(HealpixSkyMap, self).__init__(numTracts, config, version)
108 
109  def findTract(self, coord):
110  """Find the tract whose inner region includes the coord.
111 
112  Parameters
113  ----------
114  coord : `lsst.geom.SpherePoint`
115  ICRS sky coordinate to search for.
116 
117  Returns
118  -------
119  tractInfo : `TractInfo`
120  Info for tract whose inner region includes the coord.
121  """
122  theta, phi = coordToAng(coord)
123  index = healpy.ang2pix(self._nside, theta, phi, nest=self.config.nest)
124  return self[index]
125 
126  def generateTract(self, index):
127  """Generate TractInfo for the specified tract index."""
128  center = angToCoord(healpy.pix2ang(self._nside, index, nest=self.config.nest))
129  wcs = self._wcsFactory.makeWcs(crPixPos=geom.Point2D(0, 0), crValCoord=center)
130  return HealpixTractInfo(self._nside, index, self.config.nest, self.config.patchInnerDimensions,
131  self.config.patchBorder, center, self.config.tractOverlap*geom.degrees,
132  wcs)
133 
134  def updateSha1(self, sha1):
135  """Add subclass-specific state or configuration options to the SHA1."""
136  sha1.update(struct.pack("<i?", self.config.log2NSide, self.config.nest))
lsst.skymap.healpixSkyMap.HealpixSkyMap.updateSha1
def updateSha1(self, sha1)
Definition: healpixSkyMap.py:134
lsst.skymap.baseSkyMap.BaseSkyMap.config
config
Definition: baseSkyMap.py:107
lsst.skymap.healpixSkyMap.coordToAng
def coordToAng(coord)
Definition: healpixSkyMap.py:58
lsst.skymap.healpixSkyMap.DummyHealpy.__getattr__
def __getattr__(self, name, e=e)
Definition: healpixSkyMap.py:38
lsst.skymap.healpixSkyMap.angToCoord
def angToCoord(thetaphi)
Definition: healpixSkyMap.py:48
lsst.skymap.baseSkyMap.BaseSkyMap._wcsFactory
_wcsFactory
Definition: baseSkyMap.py:109
lsst.skymap.healpixSkyMap.HealpixSkyMap.__init__
def __init__(self, config, version=0)
Definition: healpixSkyMap.py:104
lsst.skymap.tractInfo.TractInfo
Definition: tractInfo.py:34
lsst.skymap.healpixSkyMap.HealpixSkyMapConfig.rotation
rotation
Definition: healpixSkyMap.py:83
lsst.skymap.healpixSkyMap.HealpixTractInfo
Definition: healpixSkyMap.py:66
lsst.skymap.cachingSkyMap.CachingSkyMap
Definition: cachingSkyMap.py:28
lsst.skymap.healpixSkyMap.HealpixSkyMap
Definition: healpixSkyMap.py:86
lsst.skymap.healpixSkyMap.HealpixSkyMap._nside
_nside
Definition: healpixSkyMap.py:105
lsst::geom
Definition: geomOperators.dox:4
lsst.skymap.healpixSkyMap.HealpixSkyMap.generateTract
def generateTract(self, index)
Definition: healpixSkyMap.py:126
lsst::meas::astrom::makeWcs
std::shared_ptr< afw::geom::SkyWcs > makeWcs(SipForwardTransform const &sipForward, SipReverseTransform const &sipReverse, geom::SpherePoint const &skyOrigin)
Create a new TAN SIP Wcs from a pair of SIP transforms and the sky origin.
Definition: SipTransform.cc:148
lsst.skymap.healpixSkyMap.HealpixTractInfo.__init__
def __init__(self, nSide, ident, nest, patchInnerDimensions, patchBorder, ctrCoord, tractOverlap, wcs)
Definition: healpixSkyMap.py:69
lsst.skymap.healpixSkyMap.HealpixSkyMapConfig
Definition: healpixSkyMap.py:77
lsst::geom::Point< double, 2 >
lsst.skymap.healpixSkyMap.DummyHealpy
Definition: healpixSkyMap.py:35
lsst::geom::SpherePoint
Point in an unspecified spherical coordinate system.
Definition: SpherePoint.h:57
lsst.skymap.healpixSkyMap.HealpixSkyMap.findTract
def findTract(self, coord)
Definition: healpixSkyMap.py:109
lsst.skymap.healpixSkyMap.HealpixSkyMapConfig.setDefaults
def setDefaults(self)
Definition: healpixSkyMap.py:82