Provided by: libncarg-dev_6.3.0-6build1_amd64 NAME

CSVORO - calculate Voronoi polygons for data on a sphere.

SYNOPSIS

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

DESCRIPTION

NPTS        (integer,input) The number of input data points (NPTS > 3).

RLATI       (real,  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       (real,  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 CSVORO 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       (real,  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       (real, output) The longitudes for the vertices of the Voronoi polygons.

RC          (real,  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.

USAGE

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

ACCESS

To use CSVORO, load the NCAR Graphics library ngmath.

SEEALSO

css_overview, csstri, cssgrid.

Complete documentation for Cssgrid is available at URL
http://ngwww.ucar.edu/ngdoc/ng/ngmath/cssgrid/csshome.html