Help for GTOFFSET

PURPOSE
     GTOFFSET reads the GeoTIFF labels of two images and prints the 
     offset of the second (in line,sample) relative to the first.
     These values can be used in programs such as FASTMOS or FEATHERV
     to perform image mosaicking.
     
     THE PROCEDURE DOES NOT CHECK THE MAPPINGS FOR CONSISTENCY.  THE
     TWO IMAGES MUST HAVE A CONSISTENT MAPPING (SAME PROJECTION, ZONE,
     STANDARD PARALLELS, SCALE, ETC.).  ONLY THE OFFSET CAN VARY.
     
     The user can name an ibis table for the result to be in.  The
     values will be double precision in columns (5,6).
     
     THE RESULTS ARE THE RELATIVE OFFSETS OF THE TWO IMAGES.  WHEN
     MOSAICKING, IF THE FIRST IMAGE IS PLACED AT (1,1) THEN THE 
     RELATIVE OFFSETS PLUS ONE MUST BE USED FOR THE MOSAIC/OFFSET OF
     THE SECOND IMAGE.  THESE ARE PRINTED IN COLUMNS 7 AND 8.
     
CALL
     gtoffset INPUT1 INPUT2
  WHERE:
     INPUT1   is the first input data set (must have a GeoTIFF label).
     INPUT2   is the second input data set (must have a GeoTIFF label).
       
OPERATION

Pixel (0,0) of the second image is converted to a geographic coordinate
using the second image geotiff label and the routine PIXMAP.  Then the
coordinate is converted to pixel again using PIXMAP but using the
geotiff label of the first image.  The result is the offset of the
second image.  The result is printed.

PERFORMANCE

Less than a second.
Restrictions
------------

The input images must have GeoTIFF labels.
The mappings of the two images must differ only
by offset.

History: 

Original Programmer: A. L. Zobrist, 07 Jul, 2000
Current Cognizant Programmer: B. A. McGuffie

2022-06-27 B. Crocco afids to opensource

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