BaseSkyMap¶

class lsst.skymap.BaseSkyMap(config=None)¶

Bases: object

A collection of overlapping Tracts that map part or all of the sky.

See TractInfo for more information.

Parameters:	config : `BaseSkyMapConfig` or None (optional) The configuration for this SkyMap; if None use the default config.

Notes

BaseSkyMap is an abstract base class. Subclasses must do the following: define __init__ and have it construct the TractInfo objects and put them in __tractInfoList__ define __getstate__ and __setstate__ to allow pickling (the butler saves sky maps using pickle); see DodecaSkyMap for an example of how to do this. (Most of that code could be moved into this base class, but that would make it harder to handle older versions of pickle data.) define updateSha1 to add any subclass-specific state to the hash.

All SkyMap subclasses must be conceptually immutable; they must always refer to the same set of mathematical tracts and patches even if the in- memory representation of those objects changes.

Attributes Summary

`SKYMAP_DATASET_TYPE_NAME`
`SKYMAP_RUN_COLLECTION_NAME`

Methods Summary

`findClosestTractPatchList`(coordList)	Find closest tract and patches that overlap coordinates.
`findTract`(coord)	Find the tract whose center is nearest the specified coord.
`findTractIdArray`(ra, dec[, degrees])	Find array of tract IDs with vectorized operations (where supported).
`findTractPatchList`(coordList)	Find tracts and patches that overlap a region.
`getSha1`()	Return a SHA1 hash that uniquely identifies this SkyMap instance.
`logSkyMapInfo`(log)	Write information about a sky map to supplied log
`register`(name, butler)	Add skymap, tract, and patch Dimension entries to the given Gen3 Butler.
`updateSha1`(sha1)	Add subclass-specific state or configuration options to the SHA1.

Attributes Documentation

SKYMAP_DATASET_TYPE_NAME = 'skyMap'¶

SKYMAP_RUN_COLLECTION_NAME = 'skymaps'¶

Methods Documentation

findClosestTractPatchList(coordList)¶

Find closest tract and patches that overlap coordinates.

Parameters:	coordList : `lsst.geom.SpherePoint` List of ICRS sky coordinates to search for.
Returns:	retList : `list` 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:	coord : `lsst.geom.SpherePoint` ICRS sky coordinate to search for.
Returns:	result : `TractInfo` 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.

findTractIdArray(ra, dec, degrees=False)¶

Find array of tract IDs with vectorized operations (where supported).

If a given sky map does not support vectorized operations, then a loop over findTract will be called.

Parameters:	ra : `np.ndarray` Array of Right Ascension. Units are radians unless degrees=True. dec : `np.ndarray` Array of Declination. Units are radians unless degrees=True. degrees : `bool`, optional Input ra, dec arrays are degrees if True.
Returns:	tractId : `np.ndarray` Array of tract IDs

Notes

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

Warning: If tracts do not cover the whole sky then the returned tract may not include the given ra/dec.

findTractPatchList(coordList)¶

Find tracts and patches that overlap a region.

Parameters:	coordList : `list` of `lsst.geom.SpherePoint` List of ICRS sky coordinates to search for.
Returns:	reList : `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.

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).

getSha1()¶

Return a SHA1 hash that uniquely identifies this SkyMap instance.

Returns:	sha1 : `bytes` 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:	log : `lsst.log.Log` Log object that information about skymap will be written

register(name, butler)¶

Add skymap, tract, and patch Dimension entries to the given Gen3 Butler.

Parameters:	name : `str` The name of the skymap. butler : `lsst.daf.butler.Butler` The butler to add to.
Raises:	lsst.daf.butler.registry.ConflictingDefinitionError Raised if a different skymap exists with the same name.

Notes

Registering the same skymap multiple times (with the exact same definition) is safe, but inefficient; most of the work of computing the rows to be inserted must be done first in order to check for consistency between the new skymap and any existing one.

Re-registering a skymap with different tract and/or patch definitions but the same summary information may not be detected as a conflict but will never result in updating the skymap; there is intentionally no way to modify a registered skymap (aside from manual administrative operations on the database), as it is hard to guarantee that this can be done without affecting reproducibility.

updateSha1(sha1)¶

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

Parameters:	sha1 : `hashlib.sha1` A hashlib object on which `update` can be called to add additional state to the hash.

Notes

This method is conceptually “protected” : it should be reimplemented by all subclasses, but called only by the base class implementation of getSha1 .

Navigation

BaseSkyMap¶