ncl_csstrid (3) - Linux Manuals

ncl_csstrid: calculates a Delaunay triangulation for data on a sphere

NAME

CSSTRID - calculates a Delaunay triangulation for data on a sphere

SYNOPSIS

CALL CSSTRID (N, RLAT, RLON, NT, NTRI, IWK, RWK, IER)

DESCRIPTION

N

(integer,input) The number of input data points (N > 2).

RLAT

(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).

RLON

(double precision, input) An array containing the longitudes of the input data, expressed in degrees.

NT

(integer, output) The number of triangles in the triangulation, unless IER .NE. 0, in which case NT = 0. Where NB is the number of boundary points on the convex hull of the data, if NB .GE. 3, then NT = 2N-NB-2, otherwise NT=2N-4. The input data are considered to be bounded if they all lie in one hemisphere. Dimensioning NT for 2*N will always work.

NTRI

(integer, output) A two-dimensional integer array dimensioned for 3 x NT where NT is the number of triangles in the triangulation (NT is at most 2*N). NTRI contains the triangulation data. The vertices of the Kth triangle are: (PLAT(NTRI((1,K)),PLON(NTRI(1,K)), (PLAT(NTRI((2,K)),PLON(NTRI(2,K)), (PLAT(NTRI((3,K)),PLON(NTRI(3,K))

IWK

(integer, input) An integer workspace of length 27*N.

RWK

(double precision, input) A work array dimensioned for 13*N. Note that this work array must be typed DOUBLE PRECISION.

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

CSSTRID is called to find a Delaunay triangulation of data randomly positioned on the surface of a sphere. CSSTRID is a double precision version of CSSTRI.

ACCESS

To use CSSTRID, load the NCAR Graphics library ngmath.

COPYRIGHT

Copyright (C) 2000
University Corporation for Atmospheric Research

The use of this Software is governed by a License Agreement.