ncl_c_cssgrid man page

c_cssgrid — tension spline interpolation on a sphere

Function Prototype

float *c_cssgrid(int, float [], float [], float [],
                 int, int, float [], float [], int *);

Synopsis

float *c_cssgrid (n, rlat, rlon, f, ni, nj, plat, plon, ier)

Description

n

The number of input data points, n > 2.

rlat

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).

rlon

An array containing the longitudes of the input data, expressed in degrees.

f

Array containing data values. f[i] is the functional  value at (rlat[i],rlon[i]) for i = 0 to n-1.

ni

The number of latitudes in the interpolated grid.

nj

The number of longitudes in the interpolated grid.  ni and nj can both be 1, allowing for interpolation at a single point.

plat

An array containing the latitudes of the points  where interpolated values are to be computed.   The values in plat should be in degrees.

plon

An array of length nj containing the longitudes the output grid lines. The values in plon should be in degrees.

ier

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.

Usage

c_cssgrid is called to find an interpolating tension spline for  randomly positioned data on a unit sphere.

Return Value

c_cssgrid returns a pointer to a linear array of data that  contains interpolated values at user-specified lat/lon pairs. The returned array stores  its values as if they were a 2-dimensional C array with latitude being the  first dimension and longitude the second dimension. That is, if out is declared as

  float *out;

and we set:

  out = c_cssgrid(n, rlat, rlon, f, nlat, nlon, plat, plon, &ier);

then out[i*nlon+j] is the interpolated function value at  coordinate point (plat[i], plon[j]) for 0 <= i < nlat and 0 <= j < nlon. The space for out  is allocated internal to c_cssgrid and is nlat * nlon floats in size.

Access

To use c_cssgrid, load the NCAR Graphics library ngmath.

See Also

css_overview, 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