ncl_css_overview man page

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

Info

May 2000 UNIX NCAR GRAPHICS