... WCSTools provides programs and subroutines which allow both scientists and programmers to access astrometric information using the world coordinate system (WCS) of an image. WCSTools programs translate between image and sky coordinates, list catalog stars in the area covered by an image, find stars in an image and list them with their sky positions, and fit a WCS by matching image objects to catalogs. ... The images of the Digitized Sky Survey also come with WCS information. ... 1997, in ASP Conf. ...