1CSVORO(3NCARG) NCAR GRAPHICS CSVORO(3NCARG)
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6 CSVORO - calculate Voronoi polygons for data on a sphere.
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9 CALL CSVORO (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 (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 RLONI (real, input) An array containing the longitudes of the
21 input data, expressed in degrees.
22 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 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 IWK (integer, input) Integer work space dimensioned for
33 27*NPTS.
34 RWK (double precision, input) A work space dimensioned for
36 9*NPTS. Note that RWK must be typed DOUBLE PRECISION.
37 NC (integer, input) The maximum size of the output arrays
39 RLATO, RLONO, and RC. NC should be 2*NPTS.
40 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 RLONO (real, output) The longitudes for the vertices of the
49 Voronoi polygons.
50 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 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 NUMV (integer, output) The number of vertices in the Voronoi
62 polygon enclosing the coordinate (RLATI(NI),RLONI(NI)).
63 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 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.
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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.
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85 To use CSVORO, load the NCAR Graphics library ngmath.
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88 css_overview, csstri, cssgrid.
89 Complete documentation for Cssgrid is available at URL
91 http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html
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94 Copyright (C) 2000
95 University Corporation for Atmospheric Research
96 The use of this Software is governed by a License Agreement.
98UNIX May 2000 CSVORO(3NCARG)