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.
