ReferenceObjectLoader

class lsst.meas.algorithms.ReferenceObjectLoader(dataIds, refCats, config, log=None)

Bases: lsst.meas.algorithms.loadReferenceObjects.ReferenceObjectLoaderBase

This class facilitates loading reference catalogs with gen 3 middleware

The middleware preflight solver will create a list of datarefs that may possibly overlap a given region. These datarefs are then used to construct and instance of this class. The class instance should then be passed into a task which needs reference catalogs. These tasks should then determine the exact region of the sky reference catalogs will be loaded for, and call a corresponding method to load the reference objects.

Methods Summary

addFluxAliases(refCat, defaultFilter, …)	Add flux columns and aliases for camera to reference mapping.
applyProperMotions(catalog, epoch)	Apply proper motion correction to a reference catalog.
getMetadataBox(bbox, wcs[, filterName, …])	Return metadata about the load
getMetadataCircle(coord, radius, filterName)	Return metadata about the load.
joinMatchListWithCatalog(matchCat, sourceCat)	Relink an unpersisted match list to sources and reference objects.
loadPixelBox(bbox, wcs[, filterName, epoch, …])	Load reference objects that are within a pixel-based rectangular region.
loadRegion(region[, filtFunc, filterName, epoch])	Load reference objects within a specified region.
loadSkyCircle(ctrCoord, radius[, …])	Load reference objects that lie within a circular region on the sky.
remapReferenceCatalogSchema(refCat, *[, …])	This function takes in a reference catalog and creates a new catalog with additional columns defined the remaining function arguments.

Methods Documentation

static addFluxAliases(refCat, defaultFilter, filterReferenceMap)

Add flux columns and aliases for camera to reference mapping.

Creates a new catalog containing the information of the input refCat as well as added flux columns and aliases between camera and reference fluxes.

Parameters:

refCat : lsst.afw.table.SimpleCatalog

Catalog of reference objects

defaultFilter : str

Name of the default reference filter

filterReferenceMap : dict of str

Dictionary with keys corresponding to a filter name and values which correspond to the name of the reference filter.

Returns:

refCat : lsst.afw.table.SimpleCatalog

Reference catalog with columns added to track reference filters.

Raises:

RuntimeError

If the specified reference filter name is not specifed as a key in the reference filter map.

applyProperMotions(catalog, epoch)

Apply proper motion correction to a reference catalog.

Adjust position and position error in the catalog for proper motion to the specified epoch, modifying the catalog in place.

Parameters:

catalog : lsst.afw.table.SimpleCatalog

Catalog of positions, containing at least these fields:

• Coordinates, retrieved by the table’s coordinate key.
• coord_raErr : Error in Right Ascension (rad).
• coord_decErr : Error in Declination (rad).

• pm_ra : Proper motion in Right Ascension (rad/yr,

  East positive)

• pm_raErr : Error in pm_ra (rad/yr), optional.

• pm_dec : Proper motion in Declination (rad/yr,

  North positive)

• pm_decErr : Error in pm_dec (rad/yr), optional.
• epoch : Mean epoch of object (an astropy.time.Time)

epoch : astropy.time.Time

Epoch to which to correct proper motion. If None, do not apply PM corrections or raise if config.requireProperMotion is True.

Raises:

RuntimeError

Raised if config.requireProperMotion is set but we cannot apply the proper motion correction for some reason.

getMetadataBox(bbox, wcs, filterName=None, photoCalib=None, epoch=None, bboxToSpherePadding=100)

Return metadata about the load

This metadata is used for reloading the catalog (e.g., for reconstituting a normalised match list.)

Parameters:

bbox : lsst.geom.Box2I or lsst.geom.Box2D

Bounding box for the pixels.

wcs : lsst.afw.geom.SkyWcs

The WCS object associated with bbox.

filterName : str or None, optional

Name of the camera filter, or None or blank for the default filter.

photoCalib : None

Deprecated, only included for api compatibility.

epoch : astropy.time.Time or None, optional

Epoch to which to correct proper motion and parallax, or None to not apply such corrections.

bboxToSpherePadding : int, optional

Padding to account for translating a set of corners into a spherical (convex) boundary that is certain to encompase the enitre area covered by the box.

Returns:

md : lsst.daf.base.PropertyList

The metadata detailing the search parameters used for this dataset.

static getMetadataCircle(coord, radius, filterName, photoCalib=None, epoch=None)

Return metadata about the load.

This metadata is used for reloading the catalog (e.g. for reconstituting a normalized match list.)

Parameters:

coord : lsst.geom.SpherePoint

ICRS center of the search region.

radius : lsst.geom.Angle

Radius of the search region.

filterName : str or None

Name of the camera filter, or None or blank for the default filter.

photoCalib : None

Deprecated, only included for api compatibility.

epoch : astropy.time.Time or None, optional

Epoch to which to correct proper motion and parallax, or None to not apply such corrections.

Returns:

md : lsst.daf.base.PropertyList

joinMatchListWithCatalog(matchCat, sourceCat)

Relink an unpersisted match list to sources and reference objects.

A match list is persisted and unpersisted as a catalog of IDs produced by afw.table.packMatches(), with match metadata (as returned by the astrometry tasks) in the catalog’s metadata attribute. This method converts such a match catalog into a match list, with links to source records and reference object records.

Parameters:

matchCat : lsst.afw.table.BaseCatalog

Unpersisted packed match list. matchCat.table.getMetadata() must contain match metadata, as returned by the astrometry tasks.

sourceCat : lsst.afw.table.SourceCatalog

Source catalog. As a side effect, the catalog will be sorted by ID.

Returns:

matchList : lsst.afw.table.ReferenceMatchVector

Match list.

loadPixelBox(bbox, wcs, filterName=None, epoch=None, photoCalib=None, bboxToSpherePadding=100)

Load reference objects that are within a pixel-based rectangular region.

This algorithm works by creating a spherical box whose corners correspond to the WCS converted corners of the input bounding box (possibly padded). It then defines a filtering function which looks at the pixel position of the reference objects and accepts only those that lie within the specified bounding box.

The spherical box region and filtering function are passed to the generic loadRegion method which loads and filters the reference objects from the datastore and returns a single catalog containing the filtered set of reference objects.

Parameters:

bbox : lsst.geom.Box2I or lsst.geom.Box2D

Box which bounds a region in pixel space.

wcs : lsst.afw.geom.SkyWcs

Wcs object defining the pixel to sky (and inverse) transform for the supplied bbox.

filterName : str or None, optional

Name of camera filter, or None or blank for the default filter.

epoch : astropy.time.Time or None, optional

Epoch to which to correct proper motion and parallax, or None to not apply such corrections.

photoCalib : None

Deprecated and ignored, only included for api compatibility.

bboxToSpherePadding : int, optional

Padding to account for translating a set of corners into a spherical (convex) boundary that is certain to encompase the enitre area covered by the box.

Returns:

referenceCatalog : lsst.afw.table.SimpleCatalog

Catalog containing reference objects inside the specified bounding box (padded by self.config.pixelMargin).

Raises:

RuntimeError

Raised if no reference catalogs could be found for the specified region.

TypeError

Raised if the loaded reference catalogs do not have matching schemas.

loadRegion(region, filtFunc=None, filterName=None, epoch=None)

Load reference objects within a specified region.

This function loads the DataIds used to construct an instance of this class which intersect or are contained within the specified region. The reference catalogs which intersect but are not fully contained within the input region are further filtered by the specified filter function. This function returns a single source catalog containing all reference objects inside the specified region.

Parameters:

region : lsst.sphgeom.Region

This can be any type that is derived from lsst.sphgeom.Region and should define the spatial region for which reference objects are to be loaded.

filtFunc : callable or None, optional

This optional parameter should be a callable object that takes a reference catalog and its corresponding region as parameters, filters the catalog by some criteria and returns the filtered reference catalog. If None, an internal filter function is used which filters according to if a reference object falls within the input region.

filterName : str or None, optional

Name of camera filter, or None or blank for the default filter.

epoch : astropy.time.Time or None, optional

Epoch to which to correct proper motion and parallax, or None to not apply such corrections.

Returns:

referenceCatalog : lsst.afw.table.SourceCatalog

Catalog containing reference objects which intersect the input region, filtered by the specified filter function.

Raises:

RuntimeError

Raised if no reference catalogs could be found for the specified region.

TypeError

Raised if the loaded reference catalogs do not have matching schemas.

loadSkyCircle(ctrCoord, radius, filterName=None, epoch=None)

Load reference objects that lie within a circular region on the sky.

This method constructs a circular region from an input center and angular radius, loads reference catalogs which are contained in or intersect the circle, and filters reference catalogs which intersect down to objects which lie within the defined circle.

Parameters:

ctrCoord : lsst.geom.SpherePoint

Point defining the center of the circular region.

radius : lsst.geom.Angle

Defines the angular radius of the circular region.

filterName : str or None, optional

Name of camera filter, or None or blank for the default filter.

epoch : astropy.time.Time or None, optional

Epoch to which to correct proper motion and parallax, or None to not apply such corrections.

Returns:

referenceCatalog : lsst.afw.table.SourceCatalog

Catalog containing reference objects inside the specified search circle.

static remapReferenceCatalogSchema(refCat, *, filterNameList=None, position=False, photometric=False)

This function takes in a reference catalog and creates a new catalog with additional columns defined the remaining function arguments.

Parameters:

refCat : lsst.afw.table.SimpleCatalog

Reference catalog to map to new catalog

Returns:

expandedCat : lsst.afw.table.SimpleCatalog

Deep copy of input reference catalog with additional columns added