1c_cssgridd(3NCARG)               NCAR GRAPHICS              c_cssgridd(3NCARG)
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NAME

6       c_cssgridd - tension spline interpolation on a sphere
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FUNCTION PROTOTYPE

9       double *c_cssgridd(int, double [], double [], double [],
10                        int, int, double [], double [], int *);
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SYNOPSIS

14       double *c_cssgridd (n, rlat, rlon, f, ni, nj, plat, plon, ier)
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DESCRIPTION

18       n           The number of input data points, n > 2.
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20       rlat        An  array  containing  the  latitudes  of  the  input data,
21                   expressed in degrees.  The first three points must  not  be
22                   collinear (lie on a common great circle).
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24       rlon        An  array  containing  the  longitudes  of  the input data,
25                   expressed in degrees.
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27       f           Array containing data values. f[i] is the functional  value
28                   at (rlat[i],rlon[i]) for i = 0 to n-1.
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30       ni          The number of latitudes in the interpolated grid.
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32       nj          The  number of longitudes in the interpolated grid.  ni and
33                   nj can both be 1, allowing for interpolation  at  a  single
34                   point.
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36       plat        An  array  containing  the  latitudes  of  the points where
37                   interpolated values are to be computed.  The values in plat
38                   should be in degrees.
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40       plon        An  array of length nj containing the longitudes the output
41                   grid lines.  The values in plon should be in degrees.
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43       ier         An error return value. If *ier is returned as  0,  then  no
44                   errors  were  detected.  If *ier is non-zero, then refer to
45                   the error list in cssgrid_errors for details.
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USAGE

48       c_cssgridd is called to find an interpolating tension spline  for  ran‐
49       domly  positioned  data on a unit sphere. c_cssgridd is a double preci‐
50       sion version of c_cssgrid.
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RETURN VALUE

53       c_cssgridd returns a pointer to a linear array of  data  that  contains
54       interpolated values at user-specified lat/lon pairs. The returned array
55       stores its values as if they were a 2-dimensional C array with latitude
56       being  the first dimension and longitude the second dimension. That is,
57       if out is declared as
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59         double *out;
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61       and we set:
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63         out = c_cssgridd(n, rlat, rlon, f, nlat, nlon, plat, plon, &ier);
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65       then out[i*nlon+j] is the interpolated  function  value  at  coordinate
66       point (plat[i], plon[j]) for 0 <= i < nlat and 0 <= j < nlon. The space
67       for out is allocated internal to c_cssgridd and is nlat * nlon  doubles
68       in size.
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ACCESS

71       To use c_cssgridd, load the NCAR Graphics library ngmath.
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SEE ALSO

74       c_cssgrid, css_overview, cssgrid_errors
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76       Complete documentation for Cssgrid is available at URL
77       http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html
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80       Copyright (C) 2000
81       University Corporation for Atmospheric Research
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83       The use of this Software is governed by a License Agreement.
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87UNIX                               May 2000                 c_cssgridd(3NCARG)
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