FIT_LIMB(3)

NAME

     fit_limb: Attempts to generate co-ordinates (x,   y) of edge
     of disk.

SYNOPSIS

     #include <soi_fun.h>
     int fit_limb (sds_image, frac_box, frac_thresh, frac_lenside,
              pxc, pyc, pradius)
     SDS *image;
     double frac_box,frac_thresh, frac_lenside;
     double * pxc,* pyc, * pradius;

DESCRIPTION

      fit_limb() attempts fit a circle to the edge of the disk in
     an image.  Data values less than frac_thresh of maximum data
     value are ignored Also, "frac_lenside" specifies  the  frac-
     tional edge of isosceles triangles in the four image corners
     the data for which are zeroed out.

     Pointers pxc, pyc, and pradius are used to return  estimates
     of the center and the radius of the fitted circle.

EXAMPLE

     int error_number
     error_number   =    (sds_image,    frac_box,    frac_thresh,
     frac_lenside,
                        &pxc, &pyc, &pradius);

AUTHORS

     Modified by Lyle Bacon from a program written in Fortran  by
     Ronan et al.

BUGS

     The algorithm used for finding the edge is not  very robust.
     For  example, it fails when used on MDI images with the gra-
     dient not subtracted.  It finds the edges of the four trian-
     gles of zero data values.

RESTRICTIONS

     The disk edge must lie entirely within the image.

HISTORY

     1993-04-26     Lyle Bacon     created for SOI V 0.8