Help for RPCINV2

PURPOSE

   "rpcinv2" calculates the longitude, latitude of the image.
It performs RPC and RPC inverse iteratively to calculate a more
correct longitude and latitude.

EXECUTION

The steps of the algorithm are as follows:
-----------------------------------------

calculate the lon, lat using RPC inverse
do 10 times
   Get elevation using bilinear interpolation from DEM using lon, lat
   Calculate a new x, y of the image using RPC with inputs
      lon, lat, and elevation
   Acquire a more correct lon, lat using RPC inverse
   If the error of old and new lon, lat is less than thresh
      then break from loop
enddo

EXAMPLES

     rpcinv2 INP=(xxx1, bob.img, dem.hlf) 'print thresh=0.1
             cols=(3,2,1,4,5) fixdted=n

   The above command will take in the IBIS file xxx1, image
file bob.img, the DEM file dem.hlf and calculate the
lon, lat.  The 'print statement tells to print the debug
statements.  The thresh tells the algorithm to quit if the error is
less than 0.1.  The cols describe which columns of the IBIS file
contains what data (see variables) and the fixdted of 'n' tells
the algorithm to not use the elevation specified in the IBIS file
but rather the elevation in the dem.hlf.  The output is to the lon,
lat columns of the input IBIS file.


RESTRICTIONS

None to date.  A null IBIS file will give an appropriate error
and abort.

Original Programmer: P. Kim, 3 Dec, 2007

Revision:
  4  Nov 2009 Fixed documentation of fixdted
                                               P. Kim
  8  Jul 2009 Fixed format string size from 5 to 8
                                               P. Kim
  19 Mar 2009 Fixed a bug in getElv function dem data
              acquisition was wrong.           P. Kim
  2022-07-27 B. Crocco afids to opensource (untested)
  

PARAMETERS: