#include "geompak.h"
FUNCTION c_grderr (grid, tol)
struct GEOGRID *grid; double *tol;
A GEOGRID structure that contains the entire geometric mapping grid.
Tolerance used when the density of the grid was reduced.
c_grderr() calculates errors which occurred during the gridding process. Sixteen control points are checked for error 3/126, 43/126, 83/126, and 123/126 of the distance from one edge of the mapping grid (output space) to the other, in both x and y dimensions. First, the input space coordinates of these 16 points are determined using the mapping grid. Then, the input space is recalculated using the polynomial which was used to create the geometric mapping grid. Residual errors are calculated between the true (polynomial derived) points and the estimated (grid derived) points. These residuals are written to the geometric mapping grid file and are an indication of the errors which occurred when the polynomial transformation mapping output space to input space was gridded. Note: The input geometric mapping grid must contain a polynomial. If the geometric mapping grid was not created with a polynomial or the polynomial was not stored, this routine will return an error.
c_grderr() returns
E_SUCC (0) --> successful completion E_FAIL (-1) --> operation failed
The c_grderr() call is for C only.