FitTanSipWcsTask¶

Bases: Task

Fit a TAN-SIP WCS given a list of reference object/source matches.

Methods Summary

`emptyMetadata`()	Empty (clear) the metadata for this Task and all sub-Tasks.
`fitWcs`(matches, initWcs[, bbox, refCat, ...])	Fit a TAN-SIP WCS from a list of reference object/source matches
`getFullMetadata`()	Get metadata for all tasks.
`getFullName`()	Get the task name as a hierarchical name including parent task names.
`getName`()	Get the name of the task.
`getTaskDict`()	Get a dictionary of all tasks as a shallow copy.
`initialWcs`(matches, wcs)	Generate a guess Wcs from the astrometric matches
`makeField`(doc)	Make a `lsst.pex.config.ConfigurableField` for this task.
`makeSubtask`(name, **keyArgs)	Create a subtask as a new instance as the `name` attribute of this task.
`plotFit`(matches, wcs, rejected)	Plot the fit
`rejectMatches`(matches, wcs, rejected)	Flag deviant matches
`timer`(name[, logLevel])	Context manager to log performance data for an arbitrary block of code.

Methods Documentation

emptyMetadata() → None¶: Empty (clear) the metadata for this Task and all sub-Tasks.

fitWcs(matches, initWcs, bbox=None, refCat=None, sourceCat=None, exposure=None)¶

Fit a TAN-SIP WCS from a list of reference object/source matches

Parameters:

matcheslist of lsst.afw.table.ReferenceMatch

The following fields are read:

match.first (reference object) coord
match.second (source) centroid

The following fields are written:

match.first (reference object) centroid,
match.second (source) centroid
match.distance (on sky separation, in radians)

initWcslsst.afw.geom.SkyWcs

initial WCS

bboxlsst.geom.Box2I

the region over which the WCS will be valid (an lsst:afw::geom::Box2I); if None or an empty box then computed from matches

refCatlsst.afw.table.SimpleCatalog

reference object catalog, or None. If provided then all centroids are updated with the new WCS, otherwise only the centroids for ref objects in matches are updated. Required fields are “centroid_x”, “centroid_y”, “coord_ra”, and “coord_dec”.

sourceCatlsst.afw.table.SourceCatalog

source catalog, or None. If provided then coords are updated with the new WCS; otherwise only the coords for sources in matches are updated. Required fields are “slot_Centroid_x”, “slot_Centroid_y”, and “coord_ra”, and “coord_dec”.

exposurelsst.afw.image.Exposure

Ignored; present for consistency with FitSipDistortionTask.

Returns:

resultlsst.pipe.base.Struct

with the following fields:

wcs : the fit WCS (lsst.afw.geom.SkyWcs)
scatterOnSky : median on-sky separation between reference objects and sources in “matches” (lsst.afw.geom.Angle)

getFullMetadata() → TaskMetadata¶

Get metadata for all tasks.

Returns:

metadataTaskMetadata: The keys are the full task name. Values are metadata for the top-level task and all subtasks, sub-subtasks, etc.

Notes

The returned metadata includes timing information (if @timer.timeMethod is used) and any metadata set by the task. The name of each item consists of the full task name with . replaced by :, followed by . and the name of the item, e.g.:

topLevelTaskName:subtaskName:subsubtaskName.itemName

using : in the full task name disambiguates the rare situation that a task has a subtask and a metadata item with the same name.

getFullName() → str¶

Get the task name as a hierarchical name including parent task names.

Returns:

fullNamestr

The full name consists of the name of the parent task and each subtask separated by periods. For example:

The full name of top-level task “top” is simply “top”.
The full name of subtask “sub” of top-level task “top” is “top.sub”.
The full name of subtask “sub2” of subtask “sub” of top-level task “top” is “top.sub.sub2”.

getName() → str¶

Get the name of the task.

Returns:

taskNamestr: Name of the task.

See also

getFullName

getTaskDict() → Dict[str, ReferenceType[Task]]¶

Get a dictionary of all tasks as a shallow copy.

Returns:

taskDictdict: Dictionary containing full task name: task object for the top-level task and all subtasks, sub-subtasks, etc.

initialWcs(matches, wcs)¶

Generate a guess Wcs from the astrometric matches

We create a Wcs anchored at the center of the matches, with the scale of the input Wcs. This is necessary because matching returns only matches with no estimated Wcs, and the input Wcs is a wild guess. We’re using the best of each: positions from the matches, and scale from the input Wcs.

Parameters:

matcheslist of lsst.afw.table.ReferenceMatch: List of sources matched to references.
wcslsst.afw.geom.SkyWcs: Current WCS.

Returns:

newWcslsst.afw.geom.SkyWcs: Initial WCS guess from estimated crpix and crval.

classmethod makeField(doc: str) → ConfigurableField¶

Make a lsst.pex.config.ConfigurableField for this task.

Parameters:

docstr: Help text for the field.

Returns:

configurableFieldlsst.pex.config.ConfigurableField: A ConfigurableField for this task.

Examples

Provides a convenient way to specify this task is a subtask of another task.

Here is an example of use:

class OtherTaskConfig(lsst.pex.config.Config):
    aSubtask = ATaskClass.makeField("brief description of task")

makeSubtask(name: str, **keyArgs: Any) → None¶

Create a subtask as a new instance as the name attribute of this task.

Parameters:

namestr

Brief name of the subtask.

keyArgs

Extra keyword arguments used to construct the task. The following arguments are automatically provided and cannot be overridden:

“config”.
“parentTask”.

Notes

The subtask must be defined by Task.config.name, an instance of ConfigurableField or RegistryField.

plotFit(matches, wcs, rejected)¶

Plot the fit

We create four plots, for all combinations of (dx, dy) against (x, y). Good points are black, while rejected points are red.

Parameters:

matcheslist of lsst.afw.table.ReferenceMatch: List of sources matched to references.
wcslsst.afw.geom.SkyWcs: Fitted WCS.
rejectedarray-like of bool: Array of matches rejected from the fit.

rejectMatches(matches, wcs, rejected)¶

Flag deviant matches

We return a boolean numpy array indicating whether the corresponding match should be rejected. The previous list of rejections is used so we can calculate uncontaminated statistics.

Parameters:

matcheslist of lsst.afw.table.ReferenceMatch: List of sources matched to references.
wcslsst.afw.geom.SkyWcs: Fitted WCS.
rejectedarray-like of bool: Array of matches rejected from the fit. Unused.

Returns:

rejectedMatchesndarray of type bool: Matched objects found to be outside of tolerance.

timer(name: str, logLevel: int = 10) → Iterator[None]¶

Context manager to log performance data for an arbitrary block of code.

Parameters:

namestr: Name of code being timed; data will be logged using item name: Start and End.
logLevel: A logging level constant.

Navigation

FitTanSipWcsTask¶