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.