DirectMatchTask¶

DirectMatchTask implements a brute force nearest neighbor match between a input source catalog and a reference catalog.

The matching permits no rotation or scaling, but uses the existing sky positions in the source catalog. This is often useful for QA, as it allows validating the pipeline astrometry and photometry against the reference catalog.

Note that this DirectMatchTask is not currently suitable for use within the AstrometryTask, as it has a different interface and serves a different purpose.

Processing summary¶

DirectMatchTask runs this sequence of operations:

Finds an on sky circle covering the input source catalog.
Loads reference objects within the circle.
Performs a simple nearest neighbor assignment within a specified tolerance.

Python API summary¶

from lsst.meas.astrom.directMatch import DirectMatchTask

classDirectMatchTask(butler=None, refObjLoader=None, **kwargs): Simple, brute force matching of a source catalog to a reference catalog...

attributeconfig: Access configuration fields and retargetable subtasks.

methodrun(catalog, filterName=None, epoch=None): Load reference objects and match to them...

Retargetable subtasks¶

refObjLoader¶

Default: lsst.meas.algorithms.loadReferenceObjects.LoadReferenceObjectsTask
Field type: ConfigurableField

Load reference objects

referenceSelection¶

Default: lsst.meas.algorithms.sourceSelector.ReferenceSourceSelectorTask
Field type: ConfigurableField

Selection of reference sources

sourceSelection¶

Default: lsst.meas.algorithms.sourceSelector.ScienceSourceSelectorTask
Field type: ConfigurableField

Selection of science sources

Configuration fields¶

matchRadius¶

Default: 0.25
Field type: float Field

Matching radius, arcsec

Examples¶

config = DirectMatchConfig()
task = DirectMatchTask(butler=butler, config=config)
matchResults = task.run(catalog)

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