CSVOROD - calculate Voronoi polygons for data on a sphere.
CALL CSVOROD (NPTS, RLATI, RLONI, NI, NF, IWK, RWK,
NC, RLATO, RLONO, RC,
NCA, NUMV, NV, IER)
- NPTS
- (integer,input) The number of input data points (NPTS > 3).
- RLATI
- (double precision, input) An array containing the latitudes of the input
data, expressed in degrees. The first three points must not be collinear
(lie on a common great circle).
- RLONI
- (double precision, input) An array containing the longitudes of the input
data, expressed in degrees.
- NI
- (integer, input) The index of the input coordinate for which you want to
determine the Voronoi polygon (1 .LE. NI .LE. NPTS).
- NF
- (integer, input) Flag indicating if this is the first call to CSVOROD to
retrieve Voronoi polygons for this dataset (1=yes, 0=no). Calls subsequent
to the first call for a given dataset are much faster than the first
call.
- IWK
- (integer, input) Integer work space dimensioned for 27*NPTS.
- RWK
- (double precision, input) A work space dimensioned for 9*NPTS. Note that
RWK must be typed DOUBLE PRECISION.
- NC
- (integer, input) The maximum size of the output arrays RLATO, RLONO, and
RC. NC should be 2*NPTS.
- RLATO
- (double precision, output) The latitudes for the vertices of the Voronoi
polygons. These are circumcenters of circles passing through the Delaunay
triangles. If a coordinate is a boundary point, then the circle may pass
through certain "pseudo points" that have been added to the
original dataset in order to complete the Voronoi polygon.
- RLONO
- (double precision, output) The longitudes for the vertices of the Voronoi
polygons.
- RC
- (double precision, output) Array containing circumradii (arc lengths in
degrees of the angle between a circumcenter and its associated triangle
vertices).
- NCA
- (integer, output) The actual number of circumcenters returned in RLATO and
RLONO. This number may be larger than NPTS if the input dataset has
boundary points since certain "pseudo points" may have been
added to the original dataset in order to complete the Voronoi polygon
set.
- NUMV
- (integer, output) The number of vertices in the Voronoi polygon enclosing
the coordinate (RLATI(NI),RLONI(NI)).
- NV
- (integer, output) An array (dimensioned for NPTS) containing NUMV indices
for the Voronoi polygon enclosing the coordinate (RLATI(NI),RLONI(NI)).
The indices returned in this array refer to the coordinates returned in
RLATO, RLONO, and RC. For example, if the integer "J" is an
element of the NV array, then (RLATO(J),RLONO(J)) is a vertex of the
Voronoi polygon enclosing (RLATI(NI),RLONI(NI)). The indices in NV list
out the vertices of the Voronoi polygon in counter-clockwise order.
- IER
- (integer, output) An error return value. If IER is returned as 0, then no
errors were detected. If IER is non-zero, then refer to the man page for
cssgrid_errors for details.
CSVOROD is called if you want to determine the Voronoi polygons
for data randomly positioned on a sphere. Each call to CSVOROD calculates
the vertices for the Voronoi polygon surrounding a specified input point.
CSVOROD is a double precision version of CSVORO.
To use CSVOROD, load the NCAR Graphics library ngmath.
css_overview, csstrid, cssgridd.
Complete documentation for Cssgrid is available at URL
http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html
Copyright (C) 2000
University Corporation for Atmospheric Research
The use of this Software is governed by a License Agreement.