Help for GETPOINT

PURPOSE

     GETPOINT finds the nearest point in an IBIS file to a point 
given in the parameters.  It returns the index of the point.  The 
parameters specify a point coordinate (x0,y0) and two columns in
the IBIS file containing points (xi,yi).  The index of the nearest 
of the (xi,yi) is returned.  IBIS indexes start from 1.

     This is useful to find three points in a control mesh or control
grid to map an image.  By using three corners of the image, three 
calls of this routine can find three well-spaced mapping points in
the grid control of the image.  These can then put a GeoTIFF label
on the image and routine GTWARPXD can be used to map the image
according to the approximate mapping (of the three points) and the
additional control of the mesh or grid.
	   
CALL
     getpoint input parms
  WHERE:
     input        is the ibis table containing two columns of (xi,yi)
     parms        specify the (x0,y0), the column numbers, and information
                  for passing the answer back


  
OPERATION

MF3 is used to calculate distances to all points and find the closest.
A tie will be broken in arbitrary fashion.

PERFORMANCE

Less than a second.

Restrictions
------------

The restore-variable must use the name ixclosest.  The column numbers 
cannot be greater than 7.

HISTORY

Original Programmer: A. L. Zobrist, 11 Nov. 2001
Current Cognizant Programmer: A. L. Zobrist
Last Changed: A. L. Zobrist, 16 Nov. 2001

2022-06-27 B. Crocco afids to opensource