proj_plane_pixel_scales¶

astropy.wcs.utils.
proj_plane_pixel_scales
(wcs)[source] [edit on github]¶ For a WCS returns pixel scales along each axis of the image pixel at the
CRPIX
location once it is projected onto the “plane of intermediate world coordinates” as defined in Greisen & Calabretta 2002, A&A, 395, 1061.Note
This function is concerned only about the transformation “image plane”>”projection plane” and not about the transformation “celestial sphere”>”projection plane”>”image plane”. Therefore, this function ignores distortions arising due to nonlinear nature of most projections.
Note
In order to compute the scales corresponding to celestial axes only, make sure that the input
WCS
object contains celestial axes only, e.g., by passing in thecelestial
WCS object.Parameters:  wcs :
WCS
A world coordinate system object.
Returns:  scale :
ndarray
A vector (
ndarray
) of projection plane increments corresponding to each pixel side (axis). The units of the returned results are the same as the units ofcdelt
,crval
, andcd
for the celestial WCS and can be obtained by inquiring the value ofcunit
property of the inputWCS
WCS object.
 wcs :