NAME

c_cssgridd - tension spline interpolation on a sphere

FUNCTION PROTOTYPE

double *c_cssgridd(int, double [], double [], double [],


                 int, int, double [], double [], int *);

SYNOPSIS

double *c_cssgridd (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_cssgridd is called to find an interpolating tension spline for randomly positioned data on a unit sphere. c_cssgridd is a double precision version of c_cssgrid.

RETURN VALUE

c_cssgridd 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

  double *out;

and we set:

  out = c_cssgridd(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_cssgridd and is nlat * nlon doubles in size.

ACCESS

To use c_cssgridd, load the NCAR Graphics library ngmath.

SEE ALSO

c_cssgrid, css_overview, 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.