Coverage for python/lsst/meas/algorithms/astrometrySourceSelector.py : 96%

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1#
2# LSST Data Management System
3#
4# Copyright 2008-2017 AURA/LSST.
5#
6# This product includes software developed by the
7# LSST Project (http://www.lsst.org/).
8#
9# This program is free software: you can redistribute it and/or modify
10# it under the terms of the GNU General Public License as published by
11# the Free Software Foundation, either version 3 of the License, or
12# (at your option) any later version.
13#
14# This program is distributed in the hope that it will be useful,
15# but WITHOUT ANY WARRANTY; without even the implied warranty of
16# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17# GNU General Public License for more details.
18#
19# You should have received a copy of the LSST License Statement and
20# the GNU General Public License along with this program. If not,
21# see <https://www.lsstcorp.org/LegalNotices/>.
22#
23"""Select sources that are useful for astrometry.
25Such sources have good signal-to-noise, are well centroided, not blended,
26and not flagged with a handful of "bad" flags.
27"""
29import numpy as np
31import lsst.pex.config as pexConfig
32from .sourceSelector import BaseSourceSelectorConfig, BaseSourceSelectorTask, sourceSelectorRegistry
33from lsst.pipe.base import Struct
34from functools import reduce
37class AstrometrySourceSelectorConfig(BaseSourceSelectorConfig):
38 badFlags = pexConfig.ListField(
39 doc="List of flags which cause a source to be rejected as bad",
40 dtype=str,
41 default=[
42 "base_PixelFlags_flag_edge",
43 "base_PixelFlags_flag_interpolatedCenter",
44 "base_PixelFlags_flag_saturatedCenter",
45 "base_PixelFlags_flag_crCenter",
46 "base_PixelFlags_flag_bad",
47 ],
48 )
49 sourceFluxType = pexConfig.Field(
50 doc="Type of source flux; typically one of Ap or Psf",
51 dtype=str,
52 default="Ap",
53 )
54 minSnr = pexConfig.Field(
55 dtype=float,
56 doc="Minimum allowed signal-to-noise ratio for sources used for matching "
57 "(in the flux specified by sourceFluxType); <= 0 for no limit",
58 default=10,
59 )
62@pexConfig.registerConfigurable("astrometry", sourceSelectorRegistry)
63class AstrometrySourceSelectorTask(BaseSourceSelectorTask):
64 """Select sources that are useful for astrometry.
66 Good astrometry sources have high signal/noise, are non-blended, and
67 did not have certain "bad" flags set during source extraction. They need not
68 be PSF sources, just have reliable centroids.
69 """
70 ConfigClass = AstrometrySourceSelectorConfig
72 def __init__(self, *args, **kwargs):
73 BaseSourceSelectorTask.__init__(self, *args, **kwargs)
75 def selectSources(self, sourceCat, matches=None, exposure=None):
76 """Return a selection of sources that are useful for astrometry.
78 Parameters:
79 -----------
80 sourceCat : `lsst.afw.table.SourceCatalog`
81 Catalog of sources to select from.
82 This catalog must be contiguous in memory.
83 matches : `list` of `lsst.afw.table.ReferenceMatch` or None
84 Ignored in this SourceSelector.
85 exposure : `lsst.afw.image.Exposure` or None
86 The exposure the catalog was built from; used for debug display.
88 Return
89 ------
90 struct : `lsst.pipe.base.Struct`
91 The struct contains the following data:
93 - selected : `array` of `bool``
94 Boolean array of sources that were selected, same length as
95 sourceCat.
96 """
97 self._getSchemaKeys(sourceCat.schema)
99 bad = reduce(lambda x, y: np.logical_or(x, sourceCat.get(y)), self.config.badFlags, False)
100 good = self._isGood(sourceCat)
101 return Struct(selected=good & ~bad)
103 def _getSchemaKeys(self, schema):
104 """Extract and save the necessary keys from schema with asKey."""
105 self.parentKey = schema["parent"].asKey()
106 self.nChildKey = schema["deblend_nChild"].asKey()
107 self.centroidXKey = schema["slot_Centroid_x"].asKey()
108 self.centroidYKey = schema["slot_Centroid_y"].asKey()
109 self.centroidXErrKey = schema["slot_Centroid_xErr"].asKey()
110 self.centroidYErrKey = schema["slot_Centroid_yErr"].asKey()
111 self.centroidFlagKey = schema["slot_Centroid_flag"].asKey()
113 self.edgeKey = schema["base_PixelFlags_flag_edge"].asKey()
114 self.interpolatedCenterKey = schema["base_PixelFlags_flag_interpolatedCenter"].asKey()
115 self.saturatedKey = schema["base_PixelFlags_flag_saturated"].asKey()
117 fluxPrefix = "slot_%sFlux_" % (self.config.sourceFluxType,)
118 self.instFluxKey = schema[fluxPrefix + "instFlux"].asKey()
119 self.fluxFlagKey = schema[fluxPrefix + "flag"].asKey()
120 self.instFluxErrKey = schema[fluxPrefix + "instFluxErr"].asKey()
122 def _isMultiple(self, sourceCat):
123 """Return True for each source that is likely multiple sources."""
124 test = (sourceCat.get(self.parentKey) != 0) | (sourceCat.get(self.nChildKey) != 0)
125 # have to currently manage footprints on a source-by-source basis.
126 for i, cat in enumerate(sourceCat):
127 footprint = cat.getFootprint()
128 test[i] |= (footprint is not None) and (len(footprint.getPeaks()) > 1)
129 return test
131 def _hasCentroid(self, sourceCat):
132 """Return True for each source that has a valid centroid"""
133 def checkNonfiniteCentroid():
134 """Return True for sources with non-finite centroids."""
135 return ~np.isfinite(sourceCat.get(self.centroidXKey)) | \
136 ~np.isfinite(sourceCat.get(self.centroidYKey))
137 assert ~checkNonfiniteCentroid().any(), \
138 "Centroids not finite for %d unflagged sources." % (checkNonfiniteCentroid().sum())
139 return np.isfinite(sourceCat.get(self.centroidXErrKey)) \
140 & np.isfinite(sourceCat.get(self.centroidYErrKey)) \
141 & ~sourceCat.get(self.centroidFlagKey)
143 def _goodSN(self, sourceCat):
144 """Return True for each source that has Signal/Noise > config.minSnr."""
145 if self.config.minSnr <= 0:
146 return True
147 else:
148 with np.errstate(invalid="ignore"): # suppress NAN warnings
149 return sourceCat.get(self.instFluxKey)/sourceCat.get(self.instFluxErrKey) > self.config.minSnr
151 def _isUsable(self, sourceCat):
152 """
153 Return True for each source that is usable for matching, even if it may
154 have a poor centroid.
156 For a source to be usable it must:
157 - have a valid centroid
158 - not be deblended
159 - have a valid flux (of the type specified in this object's constructor)
160 - have adequate signal-to-noise
161 """
163 return self._hasCentroid(sourceCat) \
164 & ~self._isMultiple(sourceCat) \
165 & self._goodSN(sourceCat) \
166 & ~sourceCat.get(self.fluxFlagKey)
168 def _isGood(self, sourceCat):
169 """
170 Return True for each source that is usable for matching and likely has a
171 good centroid.
173 The additional tests for a good centroid, beyond isUsable, are:
174 - not interpolated in the center
175 - not saturated
176 - not near the edge
177 """
179 return self._isUsable(sourceCat) \
180 & ~sourceCat.get(self.saturatedKey) \
181 & ~sourceCat.get(self.interpolatedCenterKey) \
182 & ~sourceCat.get(self.edgeKey)
184 def _isBadFlagged(self, source):
185 """Return True if any of config.badFlags are set for this source."""
186 return any(source.get(flag) for flag in self.config.badFlags)