Cssgrid(3NCARG)

NAME
cssgrid - fit a tension spline interpolation to a function

DESCRIPTION
Cssgrid is a software package in the ngmath library that implements a tension spline interpolation algorithm to fit a function to input data randomly located on the surface of a sphere.

There are user-settable parameters that control various aspects of the algorithm, the most important of which is the tension factor that controls the level a tautness of the spline fit. This varies from pure cubic spline interpolation for a tension factor of 0. to near linear interpolation for a large tension factor. By default, the tension factor is automatically computed to optimize certain fitting criteria.

The output is a set of values at coordinates on a user-specified lat/lon grid (which can be a single point). Procedures also exist for finding a Dealunay triangulation and Voronoi polygons.

Functionally equivalent Fortran, C, and NCL interfaces are provided. Fortran and C codes are available in both single and double precision.

Cssgrid is based on the work of Robert Renka and his packages STRIPACK and SSRFPACK.

SYNOPSIS

Fortran
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 CSSGRID - interpolation on a sphere
 CSSTRI - calculates Delaunay triangulation
 CSVORO - calculates Voronoi polygons
 CSS2C - converts from lat/lon to Cartesian coordinates
 CSC2S - converts from Cartesian to lat/lon coordinates
 CSSETI - set values for integer-valued parameters
 CSGETI - retrieve values for integer-valued parameters
 CSSETR - set values for real valued parameters
 CSGETR - retrieve values for real valued parameters
 CSSETD - set values for double precision-valued parameters
 CSGETD - retrieve values for double precision-valued parameters
 CSSGRIDD - interpolation on a sphere (double precision entry)
 CSSTRID - calculates Delaunay triangulation (double precision entry)
 CSVOROD - calculates Voronoi polygons (double precision entry)
 CSS2CD - converts from lat/lon to Cartesian coordinates (double precision entry)
 CSC2SD - converts from Cartesian to lat/lon coordinates (double precision entry)
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 c_cssgrid - interpolation on a sphere
 c_csstri - calculates Delaunay triangulation
 c_csvoro - calculates Voronoi polygons
 c_css2c - converts from lat/lon to Cartesian coordinates
 c_csc2s - converts from Cartesian to lat/lon coordinates
 c_csseti - set values for integer-valued parameters
 c_csgeti - retrieve values for integer-valued parameters
 c_cssetr - set values for real valued parameters
 c_csgetr - retrieve values for real valued parameters
 c_cssetd - set values for double precision-valued parameters
 c_csgetd - retrieve values for double precision-valued parameters
 c_cssgridd - interpolation on a sphere (double precision entry)
 c_csstrid - calculates Delaunay triangulation (double precision entry)
 c_csvorod - calculates Voronoi polygons (double precision entry)
 c_css2cd - converts from lat/lon to Cartesian coordinates (double precision entry)
 c_csc2sd - converts from Cartesian to lat/lon coordinates (double precision entry)

ACCESS
To use Cssgrid entries, load the NCAR Graphics library ngmath.

SEE ALSO
cssgrid_params 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.