Help for GRIDCK

PURPOSE

     GRIDCK checks that a grid (in an IBIS file) is rectangular
     (with allowance for slight irregularity) and also can return
     the nah, nav of the grid as TAE TCL variables.
     
     If the points do not form a grid, the nah and nav return as
     zero, so this can be used as a grid check for TAE TCL logic.
     
     

TAE COMMAND LINE FORMAT

     gridck INP=A
     gridck INP=A valnah=nah valnav=nav
     
     where

     A                   is the input dataset (IBIS file).
     nah                 is a TCL integer variable to get nah.
     nav                 is a TCL integer variable to get nav.

OPERATION

     The selected columns of the grid are read into an array.
     Points are scanned, with each pair predicting where the next
     will lie.  If the actual next point is roughly where predicted,
     the scanning continues.  When a point does not satisfy the
     tolerance, nah is recorded and a new line begun.  All subsequent
     lines are done in the same fashion, except that failure to have
     exactly nah+1 points causes the grid to be rejected.
     
     Then nav is calculated by (total points)/(nah+1).  Then all
     of the vertical columns of points are checked for both 
     tolerance and point count as were the horizontal rows.
     
     Usually, there are four columns in a warp grid (newline, newsamp,
     oldline, oldsamp).  Only two are used at a time in this program,
     for example, (oldline,oldsamp).


TIMING

     Dominated by the time to read the array in.
     
RESTRICTIONS

     The input array is mallocked.  Compare the size of the input
     IBIS file with system parameters.  

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

COGNIZANT PROGRAMMER:  A. L. Zobrist

REVISIONS:
  2008-01-02 WLB Switched to USES_ANSI_C AND LIB_CARTO; misc cleanup  
  2015-10-23 WLB Migrated to MIPL
  2016-08-12 WLB Fixed 64-bit bug