1CSVOROD(3NCARG) NCAR GRAPHICS CSVOROD(3NCARG)
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6 CSVOROD - calculate Voronoi polygons for data on a sphere.
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9 CALL CSVOROD (NPTS, RLATI, RLONI, NI, NF, IWK, RWK,
10 NC, RLATO, RLONO, RC,
11 NCA, NUMV, NV, IER)
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14 NPTS (integer,input) The number of input data points (NPTS > 3).
15 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).
20 RLONI (double precision, input) An array containing the longi‐
22 tudes of the input data, expressed in degrees.
23 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).
27 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.
32 IWK (integer, input) Integer work space dimensioned for
34 27*NPTS.
35 RWK (double precision, input) A work space dimensioned for
37 9*NPTS. Note that RWK must be typed DOUBLE PRECISION.
38 NC (integer, input) The maximum size of the output arrays
40 RLATO, RLONO, and RC. NC should be 2*NPTS.
41 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.
48 RLONO (double precision, output) The longitudes for the vertices
50 of the Voronoi polygons.
51 RC (double precision, output) Array containing circumradii
53 (arc lengths in degrees of the angle between a circumcenter
54 and its associated triangle vertices).
55 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.
61 NUMV (integer, output) The number of vertices in the Voronoi
63 polygon enclosing the coordinate (RLATI(NI),RLONI(NI)).
64 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.
74 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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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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87 To use CSVOROD, load the NCAR Graphics library ngmath.
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90 css_overview, csstrid, cssgridd.
91 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
98 The use of this Software is governed by a License Agreement.
100UNIX May 2000 CSVOROD(3NCARG)