lsst.afw  19.0.0-25-g6c8df7140
Functions
lsst.afw.geom.wcsUtils.wcsUtilsContinued Namespace Reference

Functions

def getSipMatrixFromMetadata (metadata, name)
 
def makeDistortedTanWcs (tanWcs, pixelToFocalPlane, focalPlaneToFieldAngle)
 
def computePixelToDistortedPixel (pixelToFocalPlane, focalPlaneToFieldAngle)
 

Function Documentation

◆ computePixelToDistortedPixel()

def lsst.afw.geom.wcsUtils.wcsUtilsContinued.computePixelToDistortedPixel (   pixelToFocalPlane,
  focalPlaneToFieldAngle 
)
Compute the transform ``pixelToDistortedPixel``, which applies optical
distortion specified by ``focalPlaneToFieldAngle``.

The resulting transform is designed to be used to convert a pure TAN WCS
to a WCS that includes a model for optical distortion. In detail,
the initial WCS will contain these frames and transforms::

    PIXELS frame -> pixelToIwc -> IWC frame ->  gridToIwc -> SkyFrame

To produce the WCS with distortion, replace ``pixelToIwc`` with::

    pixelToDistortedPixel -> pixelToIwc

Parameters
----------
pixelToFocalPlane : `lsst.afw.geom.TransformPoint2ToPoint2`
    Transform parent pixel coordinates to focal plane coordinates
focalPlaneToFieldAngle : `lsst.afw.geom.TransformPoint2ToPoint2`
    Transform focal plane coordinates to field angle coordinates

Returns
-------
pixelToDistortedPixel : `lsst.afw.geom.TransformPoint2ToPoint2`
    A transform that applies the effect of the optical distortion model.

Definition at line 157 of file wcsUtilsContinued.py.

◆ getSipMatrixFromMetadata()

def lsst.afw.geom.wcsUtils.wcsUtilsContinued.getSipMatrixFromMetadata (   metadata,
  name 
)
Extract a SIP matrix from FITS TAN-SIP WCS metadata.

Omitted coefficients are set to 0 and all coefficients may be omitted.

Parameters
----------
metadata : `lsst.daf.base.PropertySet`
    FITS metadata.
name : `str`
    Name of TAN-SIP matrix (``"A"``, ``"B"``, ``"Ap"``, or ``"Bp"``).

Returns
-------
`numpy.array`
    The SIP matrix.

Raises
------
TypeError
    If the order keyword ``<name>_ORDER`` (e.g. ``AP_ORDER``) is not found,
    the value of the order keyword cannot be read as an integer,
    the value of the order keyword is negative,
    or if a matrix parameter (e.g. ``AP_5_0``) cannot be read as a float.

Definition at line 33 of file wcsUtilsContinued.py.

◆ makeDistortedTanWcs()

def lsst.afw.geom.wcsUtils.wcsUtilsContinued.makeDistortedTanWcs (   tanWcs,
  pixelToFocalPlane,
  focalPlaneToFieldAngle 
)
Compute a WCS that includes a model of optical distortion.

This is useful in the common case that the initial WCS entirely ignores
the effect of optical distortion.

Parameters
----------
tanWcs : `lsst.afw.geom.SkyWcs`
    A pure TAN WCS, such as is usually provided in raw data.
    This should have no existing compensation for optical distortion
    (though it may include an ``ACTUAL_PIXELS`` frame to model pixel-level
    distortions).
pixelToFocalPlane : `lsst.afw.geom.TransformPoint2ToPoint2`
    Transform parent pixel coordinates to focal plane coordinates.
    This models the location of the CCD on the focal plane
    and is almost always an affine transformation.
    This can be obtained from the detector of an exposure.
focalPlaneToFieldAngle : `lsst.afw.geom.TransformPoint2ToPoint2`
    Transform focal plane coordinates to field angle coordinates.
    This is a model for optical distortion, and is often a radial
    polynomial. This can be obtained from the camera geometry.


Returns
-------
lsst.afw.geom.SkyWcs
    A copy of `tanWcs` that includes the effect of optical distortion.

Raises
------
RuntimeError
    If the current frame of `wcs` is not a SkyFrame;
LookupError
    If 2-dimensional Frames with Domain "PIXELS" and "IWC"
    are not all found.

Definition at line 66 of file wcsUtilsContinued.py.