proj_plane_pixel_area¶

astropy.wcs.utils.
proj_plane_pixel_area
(wcs)[source]¶ For a celestial WCS (see
astropy.wcs.WCS.celestial
) returns pixel area of the image pixel at theCRPIX
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 area of pixels corresponding to celestial axes only, this function uses the
celestial
WCS object of the inputwcs
. This is different from theproj_plane_pixel_scales
function that computes the scales for the axes of the input WCS itself. Parameters
 wcs
WCS
A world coordinate system object.
 wcs
 Returns
 Raises
ValueError
Pixel area is defined only for 2D pixels. Most likely the
cd
matrix of thecelestial
WCS is not a square matrix of second order.
Notes
Depending on the application, square root of the pixel area can be used to represent a single pixel scale of an equivalent square pixel whose area is equal to the area of a generally nonsquare pixel.