GbdesAstrometricFitTask¶
GbdesAstrometricFitTask fits an astrometric solution, or world coordinate system (WCS), for a series of visits.
Sources in science images are matched with a reference catalog, which allows the fitting algorithm to break degeneracies in the astrometric model.
The fit model is a series of mappings, which can include (but are not limited to) a per-detector polynomial mapping and a per-visit polynomial mapping.
The fit is done using the WCSFit class from the gbdes package (https://github.com/lsst/gbdes/tree/lsst-dev), which is an implementation of the method described in Bernstein et al. (2017).
This task requires source catalogs for the input images, a reference catalog, and a visit summary table, which provides a starting point for the WCS fit.
The task produces the fitted WCSs, which are described in AST format and are held in lsst.afw.table.ExposureCatalogs called outputWcs.
The task also outputs a table for debugging, outputCatalog, which contains the sources used in the fit, along with their residuals with the best-fit model.
Processing summary¶
GbdesAstrometricFitTask runs this sequence of operations:
- Gathers information on the visit epochs, RAs and Decs, etc.
- Associates sources in science images and the reference catalog to make matched objects using a friends-of-friends algorithm.
#. Uses the associated objects to fit the astrometric solution, which is a configurable sequence of mappings from the detector pixels to the sky.
This uses WCSFit from the gbdes package (https://github.com/lsst/gbdes/tree/lsst-dev).
#. Converts the internal astrometric mappings to AST format.
The output is in the form of one lsst.afw.table.ExposureCatalog for each visit, with a row for each detector.
The fit WCS is accessed by calling getWCS() on the catalog row corresponding to the desired visit and detector.
Python API summary¶
from lsst.drp.tasks.gbdesAstrometricFit import GbdesAstrometricFitTask
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class
GbdesAstrometricFitTask Calibrate the WCS across multiple visits of the same field using the GBDES package
...
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attribute
config Access configuration fields and retargetable subtasks.
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method
run Run the WCS fit for a given set of visits
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See also
See the GbdesAstrometricFitTask API reference for complete details.
Retargetable subtasks¶
referenceSelector¶
- Default
lsst.meas.algorithms.sourceSelector.ReferenceSourceSelectorTask- Field type
ConfigurableField
sourceSelector¶
- Default
'science'- Field type
- Single-selection
RegistryField - Choices
'science'lsst.meas.algorithms.sourceSelector.ScienceSourceSelectorTask'references'lsst.meas.algorithms.sourceSelector.ReferenceSourceSelectorTask'objectSize'lsst.meas.algorithms.objectSizeStarSelector.ObjectSizeStarSelectorTask'flagged'lsst.meas.algorithms.flaggedSourceSelector.FlaggedSourceSelectorTask'astrometry'lsst.meas.algorithms.astrometrySourceSelector.AstrometrySourceSelectorTask'matcher'lsst.meas.algorithms.matcherSourceSelector.MatcherSourceSelectorTask'diaCatalog'lsst.ip.diffim.diaCatalogSourceSelector.DiaCatalogSourceSelectorTask
Configuration fields¶
allowSelfMatches¶
connections¶
- Data type
lsst.pipe.base.config.Connections- Field type
ConfigField