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
       -----------------------------
        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)
       -----------------------------
        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.