Help for BOWTIE

PURPOSE

     BOWTIE can be applied to data with a bowtie overlap to
     give a non-overlapped grid and matching resampled image.
     Applications would include MODIS and AVHRR.

TAE COMMAND LINE FORMAT

     bowtie INP=(A,G) OUT=B
     
     where

     A                   is the image dataset
     G                   is the tiepoint dataset (IBIS file), this
                           file will be modified
     B                   is the output image dataset
     
OPERATION

     The (line,samp) part of the grid must be a perfect rectangular
     grid.  The (lat,lon) part can have varying bowtie overlap
     in a vertical direction for each column of image data.

     The grid is checked for nah and nav values.  Then the
     bowtie overlaps (using parameter NSCAN) are determined
     and a new set of points are determined for each line
     that do not overlap and give even coverage of the overlap
     area.  Each vertical row is done separately, so for an
     image with ns samples, this is done up and down with a
     new set of points for each bowtie overlap.
     
     Once the grid has been rectified so that there are no
     overlaps, the image is resampled according to the location
     of the new grid points.  The resampling is along the line
     coordinate only (one dimensional) with the sample coordinate
     fixed.
     
     Since there is overlap, the interpolation can come from 
     either of the overlapping scans.  The method used is to use
     the interpolation from the upper bowtie scan for the upper
     half of the overlap and the lower..lower.  This is best for
     the case where the overlaps might disagree a little (otherwise
     we could use a simple vertical sort of the columns to get an
     acceptable grid (tieconv is very tolerant).
     
TIMING

     tbd, expected to be very fast, dominated by reading and writing
     the data sets.
     
RESTRICTIONS

     The input array is mallocked.  Compare the size of the input
     IBIS file with system parameters.
     
     The vertical spacing of the grid must be one pixel.  Otherwise
     too much accuracy is lost.  The horizontal spacing could be
     from one to five pixels without much loss of accuracy.

WRITTEN BY:            A. L. Zobrist, 23 March 2003

COGNIZANT PROGRAMMER:  A. L. Zobrist

REVISIONS:
  2008-12-28 WLB Switched to USES_ANSI_C AND LIB_CARTO; misc cleanup
  2016-01-13 WLB Migrated to MIPL; replaced printfs with zifmessages
  2022-07-14 B. Crocco afids to opensource
  

PARAMETERS: