Name
       distortion - Distortion estimation

Synopsis
       distortion [options]

Description
       distortion  estimates the distortion (vertical lines curvature or hori-
       zontal lines curvature) by using images with bright curved lines  along
       x  or  y. The distortion is fitted as a 2nd degree 2d polynomial repre-
       senting either the distortion along x or y. This polynomial  is  stored
       in a TFITS table that can be used as is by the warping command.

Algorithm
       The  input file is an ASCII file containing either one image name (with
       several curved lines) or a list of images (with in  each  one  or  more
       curved  lines). The command begins by averaging the list of files.  The
       arcs are then detected, their shape is precisely extracted, fitted, and
       a  general  fit is then computed to obtain the final 2d polynomial. The
       arcs can be horizontal or vertical, but this has to be  specified  with
       the -O option (1 for vertical arcs, 0 for horizontal arcs).

Options
       -i input
              input is the name of the input ASCII file.

       -o output
              output is the name of the output TFITS table.

       -O orientation
              orientation  is 1 if the curved arcs are vertical and 0 if hori-
              zontal.


       SEE ALSO

       warping