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DM-53963: Calculate image/patch overlap in patch coordinates #449

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Merged
cmsaunders merged 1 commit into from
Feb 1, 2026
+9 −4
Merged

DM-53963: Calculate image/patch overlap in patch coordinates #449

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13 changes: 9 additions & 4 deletions python/lsst/ip/diffim/getTemplate.py
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Original file line number Diff line number Diff line change
Expand Up @@ -243,6 +243,7 @@ def getExposures(self, coaddExposureHandles, bbox, skymap, wcs):

# Exposure's validPolygon would be more accurate
detectorPolygon = geom.Box2D(bbox)
detectorCorners = wcs.pixelToSky(detectorPolygon.getCorners())
overlappingArea = 0
coaddExposures = collections.defaultdict(list)
dataIds = collections.defaultdict(list)
Expand All @@ -251,11 +252,15 @@ def getExposures(self, coaddExposureHandles, bbox, skymap, wcs):
dataId = coaddRef.dataId
patchWcs = skymap[dataId["tract"]].getWcs()
patchBBox = skymap[dataId["tract"]][dataId["patch"]].getOuterBBox()
patchCorners = patchWcs.pixelToSky(geom.Box2D(patchBBox).getCorners())
patchPolygon = afwGeom.Polygon(wcs.skyToPixel(patchCorners))
if patchPolygon.intersection(detectorPolygon):
patchPolygon = afwGeom.Polygon(geom.Box2D(patchBBox))
# Calculate detector/patch overlap in patch coordinates rather than
# detector coordinates because the skymap's inverse mapping
# (patchWcs.skyToPixel()) is more stable than the detector's for
# arbitrary sky coordinates.
detectorInPatchCoordinates = afwGeom.Polygon(patchWcs.skyToPixel(detectorCorners))
if patchPolygon.intersection(detectorInPatchCoordinates):
overlappingArea += patchPolygon.intersectionSingle(
detectorPolygon
detectorInPatchCoordinates
).calculateArea()
self.log.info(
"Using template input tract=%s, patch=%s",
Expand Down