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

6       CSVOROD - calculate Voronoi polygons for data on a sphere.
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SYNOPSIS

9       CALL CSVOROD (NPTS, RLATI, RLONI, NI, NF, IWK, RWK,
10                    NC, RLATO, RLONO, RC,
11                    NCA, NUMV, NV, IER)
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DESCRIPTION

14       NPTS        (integer,input) The number of input data points (NPTS > 3).
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16       RLATI       (double precision, input) An array containing the latitudes
17                   of the input data, expressed in degrees.  The  first  three
18                   points  must  not  be collinear (lie on a common great cir‐
19                   cle).
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21       RLONI       (double precision, input) An array  containing  the  longi‐
22                   tudes of the input data, expressed in degrees.
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24       NI          (integer,  input)  The  index  of  the input coordinate for
25                   which you want to determine the Voronoi polygon (1 .LE.  NI
26                   .LE. NPTS).
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28       NF          (integer,  input) Flag indicating if this is the first call
29                   to CSVOROD to retrieve Voronoi polygons  for  this  dataset
30                   (1=yes,  0=no).   Calls  subsequent to the first call for a
31                   given dataset are much faster than the first call.
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33       IWK         (integer,  input)  Integer  work  space   dimensioned   for
34                   27*NPTS.
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36       RWK         (double  precision,  input)  A  work  space dimensioned for
37                   9*NPTS.  Note that RWK must be typed DOUBLE PRECISION.
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39       NC          (integer, input) The maximum  size  of  the  output  arrays
40                   RLATO, RLONO, and RC. NC should be 2*NPTS.
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42       RLATO       (double  precision,  output) The latitudes for the vertices
43                   of the Voronoi polygons.  These are circumcenters  of  cir‐
44                   cles  passing  through the Delaunay triangles. If a coordi‐
45                   nate is a boundary point, then the circle may pass  through
46                   certain  "pseudo points" that have been added to the origi‐
47                   nal dataset in order to complete the Voronoi polygon.
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49       RLONO       (double precision, output) The longitudes for the  vertices
50                   of the Voronoi polygons.
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52       RC          (double  precision,  output)  Array  containing circumradii
53                   (arc lengths in degrees of the angle between a circumcenter
54                   and its associated triangle vertices).
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56       NCA         (integer,   output)  The  actual  number  of  circumcenters
57                   returned in RLATO and RLONO. This number may be larger than
58                   NPTS if the input dataset has boundary points since certain
59                   "pseudo points" may have been added to the original dataset
60                   in order to complete the Voronoi polygon set.
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62       NUMV        (integer,  output)  The  number  of vertices in the Voronoi
63                   polygon enclosing the coordinate (RLATI(NI),RLONI(NI)).
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65       NV          (integer, output) An array (dimensioned for NPTS)  contain‐
66                   ing  NUMV  indices  for  the  Voronoi polygon enclosing the
67                   coordinate (RLATI(NI),RLONI(NI)). The indices  returned  in
68                   this  array  refer  to  the  coordinates returned in RLATO,
69                   RLONO, and RC. For example, if the integer "J" is  an  ele‐
70                   ment  of the NV array, then (RLATO(J),RLONO(J)) is a vertex
71                   of the Voronoi polygon enclosing (RLATI(NI),RLONI(NI)). The
72                   indices  in NV list out the vertices of the Voronoi polygon
73                   in counter-clockwise order.
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75       IER         (integer,  output)  An  error  return  value.   If  IER  is
76                   returned as 0, then no errors were detected. If IER is non-
77                   zero, then refer to the man  page  for  cssgrid_errors  for
78                   details.
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USAGE

81       CSVOROD  is  called  if  you want to determine the Voronoi polygons for
82       data randomly positioned on a sphere. Each call to  CSVOROD  calculates
83       the  vertices  for  the  Voronoi  polygon surrounding a specified input
84       point.  CSVOROD is a double precision version of CSVORO.
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ACCESS

87       To use CSVOROD, load the NCAR Graphics library ngmath.
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SEE ALSO

90       css_overview, csstrid, cssgridd.
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92       Complete documentation for Cssgrid is available at URL
93       http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html
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96       Copyright (C) 2000
97       University Corporation for Atmospheric Research
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99       This documentation is free software; you  can  redistribute  it  and/or
100       modify  it  under  the  terms of the GNU General Public License as pub‐
101       lished by the  Free  Software  Foundation;  either  version  2  of  the
102       License, or (at your option) any later version.
103
104       This  software  is  distributed in the hope that it will be useful, but
105       WITHOUT ANY  WARRANTY;  without  even  the  implied  warranty  of  MER‐
106       CHANTABILITY  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
107       Public License for more details.
108
109       You should have received a copy of the GNU General Public License along
110       with  this  software;  if  not,  write to the Free Software Foundation,
111       Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
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116UNIX                               May 2000                    CSVOROD(3NCARG)
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