1CSVORO(3NCARG)                   NCAR GRAPHICS                  CSVORO(3NCARG)
2
3
4

NAME

6       CSVORO - calculate Voronoi polygons for data on a sphere.
7

SYNOPSIS

9       CALL CSVORO (NPTS, RLATI, RLONI, NI, NF, IWK, RWK,
10                    NC, RLATO, RLONO, RC,
11                    NCA, NUMV, NV, IER)
12

DESCRIPTION

14       NPTS        (integer,input) The number of input data points (NPTS > 3).
15
16       RLATI       (real,  input)  An  array  containing  the latitudes of the
17                   input data, expressed in degrees.  The first  three  points
18                   must not be collinear (lie on a common great circle).
19
20       RLONI       (real,  input)  An  array  containing the longitudes of the
21                   input data, expressed in degrees.
22
23       NI          (integer, input) The index  of  the  input  coordinate  for
24                   which  you want to determine the Voronoi polygon (1 .LE. NI
25                   .LE. NPTS).
26
27       NF          (integer, input) Flag indicating if this is the first  call
28                   to  CSVORO  to  retrieve  Voronoi polygons for this dataset
29                   (1=yes, 0=no).  Calls subsequent to the first  call  for  a
30                   given dataset are much faster than the first call.
31
32       IWK         (integer,   input)   Integer  work  space  dimensioned  for
33                   27*NPTS.
34
35       RWK         (double precision, input)  A  work  space  dimensioned  for
36                   9*NPTS.  Note that RWK must be typed DOUBLE PRECISION.
37
38       NC          (integer,  input)  The  maximum  size  of the output arrays
39                   RLATO, RLONO, and RC. NC should be 2*NPTS.
40
41       RLATO       (real, output)  The  latitudes  for  the  vertices  of  the
42                   Voronoi polygons.  These are circumcenters of circles pass‐
43                   ing through the Delaunay triangles. If a  coordinate  is  a
44                   boundary  point,  then  the circle may pass through certain
45                   "pseudo points"  that  have  been  added  to  the  original
46                   dataset in order to complete the Voronoi polygon.
47
48       RLONO       (real,  output)  The  longitudes  for  the  vertices of the
49                   Voronoi polygons.
50
51       RC          (real, output) Array containing circumradii (arc lengths in
52                   degrees of the angle between a circumcenter and its associ‐
53                   ated triangle vertices).
54
55       NCA         (integer,  output)  The  actual  number  of   circumcenters
56                   returned in RLATO and RLONO. This number may be larger than
57                   NPTS if the input dataset has boundary points since certain
58                   "pseudo points" may have been added to the original dataset
59                   in order to complete the Voronoi polygon set.
60
61       NUMV        (integer, output) The number of  vertices  in  the  Voronoi
62                   polygon enclosing the coordinate (RLATI(NI),RLONI(NI)).
63
64       NV          (integer,  output) An array (dimensioned for NPTS) contain‐
65                   ing NUMV indices for  the  Voronoi  polygon  enclosing  the
66                   coordinate  (RLATI(NI),RLONI(NI)).  The indices returned in
67                   this array refer to  the  coordinates  returned  in  RLATO,
68                   RLONO,  and  RC. For example, if the integer "J" is an ele‐
69                   ment of the NV array, then (RLATO(J),RLONO(J)) is a  vertex
70                   of the Voronoi polygon enclosing (RLATI(NI),RLONI(NI)). The
71                   indices in NV list out the vertices of the Voronoi  polygon
72                   in counter-clockwise order.
73
74       IER         (integer,  output)  An  error  return  value.   If  IER  is
75                   returned as 0, then no errors were detected. If IER is non-
76                   zero,  then  refer  to  the man page for cssgrid_errors for
77                   details.
78

USAGE

80       CSVORO is called if you want to determine the Voronoi polygons for data
81       randomly  positioned  on  a  sphere. Each call to CSVORO calculates the
82       vertices for the Voronoi polygon surrounding a specified input point.
83

ACCESS

85       To use CSVORO, load the NCAR Graphics library ngmath.
86

SEE ALSO

88       css_overview, csstri, cssgrid.
89
90       Complete documentation for Cssgrid is available at URL
91       http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html
92

94       Copyright (C) 2000
95       University Corporation for Atmospheric Research
96
97       This documentation is free software; you  can  redistribute  it  and/or
98       modify  it  under  the  terms of the GNU General Public License as pub‐
99       lished by the  Free  Software  Foundation;  either  version  2  of  the
100       License, or (at your option) any later version.
101
102       This  software  is  distributed in the hope that it will be useful, but
103       WITHOUT ANY  WARRANTY;  without  even  the  implied  warranty  of  MER‐
104       CHANTABILITY  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General
105       Public License for more details.
106
107       You should have received a copy of the GNU General Public License along
108       with  this  software;  if  not,  write to the Free Software Foundation,
109       Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
110
111
112
113
114UNIX                               May 2000                     CSVORO(3NCARG)
Impressum