approximateWcs

lsst.meas.astrom.approximateWcs(wcs, bbox, order=3, nx=20, ny=20, iterations=3, skyTolerance=Angle(2.7777777777777781e-07, degrees), pixelTolerance=0.02, useTanWcs=False)

Approximate an existing WCS as a TAN-SIP WCS

The fit is performed by evaluating the WCS at a uniform grid of points within a bounding box.

Parameters:

wcslsst.afw.geom.SkyWcs

wcs to approximate

bboxlsst.geom.Box2I

the region over which the WCS will be fit

orderint

order of SIP fit

nxint

number of grid points along x

nyint

number of grid points along y

iterationsint

number of times to iterate over fitting

skyTolerancelsst.geom.Angle

maximum allowed difference in world coordinates between input wcs and approximate wcs (default is 0.001 arcsec)

pixelTolerancefloat

maximum allowed difference in pixel coordinates between input wcs and approximate wcs (default is 0.02 pixels)

useTanWcsbool

send a TAN version of wcs to the fitter? It is documented to require that, but I don’t think the fitter actually cares

Returns:

fitWcslsst.afw.geom.SkyWcs

the fit TAN-SIP WCS