DiscreteSkyMap

class lsst.skymap.DiscreteSkyMap(config, version=0)

Bases: lsst.skymap.cachingSkyMap.CachingSkyMap

Discrete sky map pixelization.

We put a square Tract at each of the nominated coordinates.

Parameters

configlsst.skyMap.BaseSkyMapConfig

The configuration for this SkyMap; if None use the default config.

versionint or tuple of int (optional)

Software version of this class, to retain compatibility with old instances.

Methods Summary

findClosestTractPatchList(coordList)	Find closest tract and patches that overlap coordinates.
findTract(coord)	Find the tract whose center is nearest the specified coord.
findTractPatchList(coordList)	Find tracts and patches that overlap a region.
generateTract(index)	Generate TractInfo for the specified tract index.
getSha1()	Return a SHA1 hash that uniquely identifies this SkyMap instance.
logSkyMapInfo(log)	Write information about a sky map to supplied log
register(name, registry)	Add SkyMap, Tract, and Patch Dimension entries to the given Gen3 Butler Registry.
updateSha1(sha1)	Add subclass-specific state or configuration options to the SHA1.

Methods Documentation

findClosestTractPatchList(coordList)

Find closest tract and patches that overlap coordinates.

Parameters

coordListlsst.geom.SpherePoint

List of ICRS sky coordinates to search for.

Returns

retListlist

list of (TractInfo, list of PatchInfo) for tracts and patches that contain, or may contain, the specified region. The list will be empty if there is no overlap.

findTract(coord)

Find the tract whose center is nearest the specified coord.

Parameters

coordlsst.geom.SpherePoint

ICRS sky coordinate to search for.

Returns

resultTractInfo

TractInfo of tract whose center is nearest the specified coord.

Notes

• If coord is equidistant between multiple sky tract centers then one is arbitrarily chosen.

• The default implementation is not very efficient; subclasses may wish to override.

Warning: If tracts do not cover the whole sky then the returned tract may not include the coord.

findTractPatchList(coordList)

Find tracts and patches that overlap a region.

Parameters

coordListlist of lsst.geom.SpherePoint

List of ICRS sky coordinates to search for.

Returns

reListlist of (TractInfo, list of PatchInfo)

For tracts and patches that contain, or may contain, the specified region. The list will be empty if there is no overlap.

Notes

warning:

This uses a naive algorithm that may find some tracts and patches that do not overlap the region (especially if the region is not a rectangle aligned along patch x, y).

generateTract(index)

Generate TractInfo for the specified tract index.

getSha1()

Return a SHA1 hash that uniquely identifies this SkyMap instance.

Returns

sha1bytes

A 20-byte hash that uniquely identifies this SkyMap instance.

Notes

Subclasses should almost always override updateSha1 instead of this function to add subclass-specific state to the hash.

logSkyMapInfo(log)

Write information about a sky map to supplied log

Parameters

loglsst.log.Log

Log object that information about skymap will be written

register(name, registry)

Add SkyMap, Tract, and Patch Dimension entries to the given Gen3 Butler Registry.

Parameters

namestr

The name of the skymap.

registrylsst.daf.butler.Registry

The registry to add to.

updateSha1(sha1)

Add subclass-specific state or configuration options to the SHA1.