c_csstrid - calculates a Delaunay triangulation for data on a sphere
int *c_csstrid(int, double , double , int *, int *);
int *c_csstrid(n, rlat, rlon, nt, ier);
- The number of input data points, n > 2.
- 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).
- An array containing the longitudes of the input data, expressed in degrees.
- *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.
- 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.
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.
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,rlon), (rlat,rlon), and (rlat,rlon) would be vertices of a triangle in the Delaunay triangulation.
To use c_csstrid, load the NCAR Graphics library ngmath.
css_overview, c_cssgrid, c_csstri, cssgrid_errors
Complete documentation for Cssgrid is available at URL
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University Corporation for Atmospheric Research
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