NAME

       c_csstrid - calculates a Delaunay triangulation for data on a sphere

FUNCTION PROTOTYPE

           int *c_csstrid(int, double [], double [], int *, int *);

SYNOPSIS

           int *c_csstrid(n, rlat, rlon, nt, ier);

DESCRIPTION

       n           The number of input data points, n > 2.

       rlat        An  array  containing  the  latitudes of the input data, expressed in degrees.
                   The first three points must not be collinear (lie on a common great circle).

       rlon        An array containing the longitudes of the input data, expressed in degrees.

       nt          *nt is the number of triangles in the triangulation, unless *ier is  non-zero,
                   in  which  case  *nt  =  0.   Where nb is the number of boundary points on the
                   convex hull of the data, if  nb  is  greater  than  3,  then  *nt  =  2n-nb-2,
                   otherwise *nt = 2n-4.  The input data are considered to be bounded if they all
                   lie in one hemisphere.

       ier         An error return value. If *ier is returned as 0, then no errors were detected.
                   If  *ier  is  non-zero,  then  refer  to  the error list in cssgrid_errors for
                   details.

USAGE

       c_csstrid is called to find a Delaunay triangulation of data randomly  positioned  on  the
       surface of a sphere. c_csstrid is a double precision version of c_csstri.

RETURN VALUE

       c_csstrid returns a pointer to a linear array that contains a sequence of integer triples.
       The elements of a triple are indices of vertices of a triangle. Each index  references  an
       original  data  point  as it occurs in sequence in the input data set (numbering starts at
       0).  For  example,  if  the  triple  <5,0,2>  were  in   the   list   of   triples,   then
       (rlat[5],rlon[5]),  (rlat[0],rlon[0]),  and  (rlat[2],rlon[2])  would  be  vertices  of  a
       triangle in the Delaunay triangulation.

ACCESS

       To use c_csstrid, load the NCAR Graphics library ngmath.

SEE ALSO

       css_overview, c_cssgrid, c_csstri, cssgrid_errors

       Complete documentation for Cssgrid is available at URL
       http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html

COPYRIGHT

       Copyright (C) 2000
       University Corporation for Atmospheric Research

       The use of this Software is governed by a License Agreement.