Help for POLYGEOV

PURPOSE

     POLYGEOV mimics two programs: TIECONV and GEOMV
     
     It calculates a GEOMV warp like TIECONV.  The warp is
     not written out, and is only used internally.
     
     It maps a point set in an IBIS file like GEOMV.  It uses
     the internal warp to map the points.
     
TAE COMMAND LINE FORMAT

     polygeov INP=(tiep,points) PARAMS

     where

     tiep		 is an IBIS tabular file containing
			   the input tiepoints.
     points		 is an IBIS tabular file containing
			   the points to be moved and two
			   columns to receive the moved points.
     B                   is the output parameter dataset.
     PARAMS              is a standard VICAR parameter field.
OPERATION

     polygeov operates in two phases.   In phase 1, the input 
     points  are  fully  triangulated  by  a version  of the 
     Thiessen   algorithm.   This operates by  computing the
     Voronoi polygons (polygons of area  nearest each point)
     and  computing  the  triangles  formed by the bisectors
     of the  polygons.   Four extra points  are  added  five 
     diameters away from the convex hull so that the surface 
     will extend smoothly beyond the input tiepoints.

     In  phase 2,  the output grid is formed by  evaluating 
     the  triangular surface at grid point locations.   That 
     is,  a grid point will fall in some triangle,  and  the 
     GEOM  shift  will  be the linear interpolation  of  the 
     input shifts at the three corners of the triangle.  The 
     user  should  note  that  the  triangular  surface   is 
     continuous but not differentiable and it passes through 
     all  of  the input  points.   Point-surface  generation 
     routines can e compared in the following table.
|       \ PROPERTIES| CONTI-|DIFFEREN-| EVALUATES |   WELL   |
|        \    OF    | NUOUS |TIABLE   | AT INPUT  |  BEHAVE  |
| METHOD  \ SURFACE |       |         |   POINT   | NO MESAS |
|-------------------|-------|---------|-----------|----------|
| Triangulation     |  yes  |    no   |    yes    |   yes    |
|-------------------|-------|---------|-----------|----------|
|                -1 |       |         |           |          |
| Interpolation r   |   no  |    no   |    yes    |   yes    |
|-------------------|-------|---------|-----------|----------|
|                -p |       |         |           |          |
| Interpolation r   |   no  |    no   |    yes    |    no    |
|-------------------|-------|---------|-----------|----------|
| Polynomial Fit    |  yes  |    yes  |    no     |    no    |
|-------------------|-------|---------|-----------|----------|
| Linear            |  yes  |    yes  |    no     |   yes    |
|-------------------|-------|---------|-----------|----------|
| Bilin (keystone)  |  yes  |    yes  |    no     |   yes    |
|-------------------|-------|---------|-----------|----------|
| Quadratic         |  yes  |    yes  |    no     |   yes    |
|-------------------|-------|---------|-----------|----------|
| Cubic             |  yes  |    yes  |    no     |   yes    |
|-------------------|-------|---------|-----------|----------|

EXAMPLE

     POLYGEOV can be used to prepare a polynomial surface fit
     of four types.  The keyword is POLY  and  it  has  five
     values: "LINEAR","KEYSTONE","QUAD","CUBIC", (or ""  for
     triangulation).  LINEAR fits the  best plane (in the L2
     norm or least squares) through the x-distortion and the
     y-distortion.   KEYSTONE fits a  bilinear surface, QUAD
     fits a general quadratic surface and CUBIC fits  a gen-
     eral cubic surface.  The  number of  tiepoints required
     are LINEAR - 3, KEYSTONE - 4, QUAD - 6, and CUBIC - 10.
     More tiepoints  are handled  by a least squares fit.
     
     
     Back to the  triangulation case, if the  input data set
     is a  grid, or  approximately  a  grid, a  shortcut  is
     applied that  speeds up  enormously.  The detection  of
     the grid is automatic.
     

     GEN OUT=X NL=1000 NS=1000 IVAL=0 LINC=0 SINC=0
     polygeov OUT=B 'GEOMZ              TIEPOINT=(
               1   1    0
               1000   1    0
               1    1000     0
               1000  1000      0
               500   500       255)
     GEOMZ INP=X PARMS=B OUT=Y

     this  example constructs a "pyramid" shaped  brightness 
     surface in the image Y.

TIMING

     Timing  is dominated by the triangulation method  which 
     is 0(n*log(n)) where n is the number of input points.  A case 
     with  10000  points  was run in 1.63 minutes  CPU  time, 
     and a case with 400,000 points was run in 4.52 hours on
     a SPARCstation 20.
     
     If the input data set is a grid, or approximately a grid,
     a shortcut is applied that speeds up enormously.  The
     detection of the grid is automatic.
     
     The polynomial fits (LINEAR, KEYSTONE, QUAD, CUBIC) are
     very fast.
     
     The final move of the data points in the second data set is
     very fast.
     
RESTRICTIONS

   The maximum number of input tiepoints is probably about 1 million.
   This value will increase as the machines get more virtual and
   real memory since dynamic memory allocation is used throughout
   the algorithm.
   
   The maximum number of output tiepoints is limited by IBIS table
   size (currently about 10 million?).  Internal to the program,
   dynamic memory allocation is used.


WRITTEN BY:            A. L. Zobrist, 8 August 2005

COGNIZANT PROGRAMMER:  A. L. Zobrist

REVISIONS: 
  2008-01-11 WLB Switched to USES_ANSI_C AND LIB_CARTO; misc cleanup.
  2016-05-16 WLB Migrated to MIPL; replaced printf with zifmessage.

PARAMETERS: