Coverage for python/lsst/meas/astrom/approximateWcs.py: 22%
43 statements
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« prev ^ index » next coverage.py v6.5.0, created at 2022-11-08 22:49 -0800
1#
2# LSST Data Management System
3# Copyright 2008-2017 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#
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19# the GNU General Public License along with this program. If not,
20# see <http://www.lsstcorp.org/LegalNotices/>.
21#
23__all__ = ["approximateWcs"]
25import numpy as np
27import lsst.geom
28import lsst.afw.table as afwTable
29import lsst.afw.geom as afwGeom
30from lsst.meas.base import SingleFrameMeasurementTask
31from lsst.meas.astrom.sip import makeCreateWcsWithSip
32from lsst.afw.geom.utils import assertWcsAlmostEqualOverBBox
35class _MockTestCase:
36 """A fake unit test case class that will enable us to call
37 assertWcsAlmostEqualOverBBox from the method approximateWcs"""
39 def fail(self, msgStr):
40 raise UserWarning("WCS fitting failed " + msgStr)
43def approximateWcs(wcs, bbox, order=3, nx=20, ny=20, iterations=3,
44 skyTolerance=0.001*lsst.geom.arcseconds, pixelTolerance=0.02, useTanWcs=False):
45 """Approximate an existing WCS as a TAN-SIP WCS
47 The fit is performed by evaluating the WCS at a uniform grid of points
48 within a bounding box.
50 Parameters
51 ----------
52 wcs : `lsst.afw.geom.SkyWcs`
53 wcs to approximate
54 bbox : `lsst.geom.Box2I`
55 the region over which the WCS will be fit
56 order : `int`
57 order of SIP fit
58 nx : `int`
59 number of grid points along x
60 ny : `int`
61 number of grid points along y
62 iterations : `int`
63 number of times to iterate over fitting
64 skyTolerance : `lsst.geom.Angle`
65 maximum allowed difference in world coordinates between
66 input wcs and approximate wcs (default is 0.001 arcsec)
67 pixelTolerance : `float`
68 maximum allowed difference in pixel coordinates between
69 input wcs and approximate wcs (default is 0.02 pixels)
70 useTanWcs : `bool`
71 send a TAN version of wcs to the fitter? It is documented to require that,
72 but I don't think the fitter actually cares
74 Returns
75 -------
76 fitWcs : `lsst.afw.geom.SkyWcs`
77 the fit TAN-SIP WCS
78 """
79 if useTanWcs:
80 crpix = wcs.getPixelOrigin()
81 crval = wcs.getSkyOrigin()
82 cdMatrix = wcs.getCdMatrix(crpix)
83 tanWcs = afwGeom.makeSkyWcs(crpix=crpix, crval=crval, cdMatrix=cdMatrix)
84 else:
85 tanWcs = wcs
87 # create a matchList consisting of a grid of points covering the bbox
88 refSchema = afwTable.SimpleTable.makeMinimalSchema()
89 refCoordKey = afwTable.CoordKey(refSchema["coord"])
90 refCat = afwTable.SimpleCatalog(refSchema)
92 sourceSchema = afwTable.SourceTable.makeMinimalSchema()
93 SingleFrameMeasurementTask(schema=sourceSchema) # expand the schema
94 sourceCentroidKey = afwTable.Point2DKey(sourceSchema["slot_Centroid"])
96 sourceCat = afwTable.SourceCatalog(sourceSchema)
98 matchList = []
100 bboxd = lsst.geom.Box2D(bbox)
101 for x in np.linspace(bboxd.getMinX(), bboxd.getMaxX(), nx):
102 for y in np.linspace(bboxd.getMinY(), bboxd.getMaxY(), ny):
103 pixelPos = lsst.geom.Point2D(x, y)
104 skyCoord = wcs.pixelToSky(pixelPos)
106 refObj = refCat.addNew()
107 refObj.set(refCoordKey, skyCoord)
109 source = sourceCat.addNew()
110 source.set(sourceCentroidKey, pixelPos)
112 matchList.append(afwTable.ReferenceMatch(refObj, source, 0.0))
114 # The TAN-SIP fitter is fitting x and y separately, so we have to iterate to make it converge
115 for indx in range(iterations):
116 sipObject = makeCreateWcsWithSip(matchList, tanWcs, order, bbox)
117 tanWcs = sipObject.getNewWcs()
118 fitWcs = sipObject.getNewWcs()
120 mockTest = _MockTestCase()
121 assertWcsAlmostEqualOverBBox(mockTest, wcs, fitWcs, bbox, maxDiffSky=skyTolerance,
122 maxDiffPix=pixelTolerance)
124 return fitWcs