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

6       c_csstri - calculates a Delaunay triangulation for data on a sphere
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FUNCTION PROTOTYPE

9           int *c_csstri(int, float [], float [], int *, int *);
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SYNOPSIS

13           int *c_csstri(n, rlat, rlon, nt, ier);
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DESCRIPTION

17       n           The number of input data points, n > 2.
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19       rlat        An  array  containing  the  latitudes  of  the  input data,
20                   expressed in degrees.  The first three points must  not  be
21                   collinear (lie on a common great circle).
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23       rlon        An  array  containing  the  longitudes  of  the input data,
24                   expressed in degrees.
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26       nt          *nt is the number of triangles in the triangulation, unless
27                   *ier  is  non-zero, in which case *nt = 0.  Where nb is the
28                   number of boundary points on the convex hull of  the  data,
29                   if  nb is greater than 3, then *nt = 2n-nb-2, otherwise *nt
30                   = 2n-4.  The input data are considered  to  be  bounded  if
31                   they all lie in one hemisphere.
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33       ier         An  error  return  value. If *ier is returned as 0, then no
34                   errors were detected. If *ier is non-zero,  then  refer  to
35                   the error list in cssgrid_errors for details.
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USAGE

38       c_csstri  is  called  to find a Delaunay triangulation of data randomly
39       positioned on the surface of a sphere.
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RETURN VALUE

42       c_csstri returns a pointer to a linear array that contains  a  sequence
43       of integer triples. The elements of a triple are indices of vertices of
44       a triangle. Each index references an original data point as  it  occurs
45       in sequence in the input data set (numbering starts at 0). For example,
46       if  the  triple  <5,0,2>  were   in   the   list   of   triples,   then
47       (rlat[5],rlon[5]),  (rlat[0],rlon[0]),  and  (rlat[2],rlon[2]) would be
48       vertices of a triangle in the Delaunay triangulation.
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ACCESS

51       To use c_csstri, load the NCAR Graphics library ngmath.
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SEE ALSO

54       css_overview, c_cssgrid, cssgrid_errors
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56       Complete documentation for Cssgrid is available at URL
57       http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html
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60       Copyright (C) 2000
61       University Corporation for Atmospheric Research
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63       This documentation is free software; you  can  redistribute  it  and/or
64       modify  it  under  the  terms of the GNU General Public License as pub‐
65       lished by the  Free  Software  Foundation;  either  version  2  of  the
66       License, or (at your option) any later version.
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68       This  software  is  distributed in the hope that it will be useful, but
69       WITHOUT ANY  WARRANTY;  without  even  the  implied  warranty  of  MER‐
70       CHANTABILITY  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
71       Public License for more details.
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73       You should have received a copy of the GNU General Public License along
74       with  this  software;  if  not,  write to the Free Software Foundation,
75       Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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80UNIX                               May 2000                   c_csstri(3NCARG)
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