FitAffineWcsTask

class lsst.meas.astrom.FitAffineWcsTask(config: Config | None = None, *, name: str | None = None, parentTask: Task | None = None, log: logging.Logger | lsst.utils.logging.LsstLogAdapter | None = None)

Bases: Task

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

This WCS fitter should be used on top of a cameraGeom distortion model as the model assumes that only a shift the WCS center position and a small affine transform are required.

Methods Summary

emptyMetadata()

Empty (clear) the metadata for this Task and all sub-Tasks.

fitWcs(matches, initWcs[, bbox, refCat, ...])

Fit a simple Affine transform with a shift to the matches and update the WCS.

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.

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.

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 simple Affine transform with a shift to the matches and update the WCS.

This method assumes that the distortion model of the telescope is applied correctly and is accurate with only a slight rotation, rotation, and “squish” required to fit to the reference locations.

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

Ignored; present for consistency with FitSipDistortionTask.

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, weakref.ReferenceType[lsst.pipe.base.task.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.

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.

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.

See also

lsst.utils.timer.logInfo

Examples

Creating a timer context:

with self.timer("someCodeToTime"):
    pass  # code to time