GRASS Programmer's Manual
6.4.2(2012)
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GIS Library - Polygon area calculation routines. More...
Go to the source code of this file.
Defines | |
#define | TWOPI M_PI + M_PI |
Functions | |
int | G_begin_ellipsoid_polygon_area (double a, double e2) |
Begin area calculations. | |
double | G_ellipsoid_polygon_area (const double *lon, const double *lat, int n) |
Area of lat-long polygon. |
GIS Library - Polygon area calculation routines.
(C) 2001-2008 by the GRASS Development Team
This program is free software under the GNU General Public License (>=v2). Read the file COPYING that comes with GRASS for details.
Definition in file area_poly1.c.
#define TWOPI M_PI + M_PI |
Definition at line 22 of file area_poly1.c.
Referenced by G_ellipsoid_polygon_area().
int G_begin_ellipsoid_polygon_area | ( | double | a, |
double | e2 | ||
) |
Begin area calculations.
This initializes the polygon area calculations for the ellipsoid with semi-major axis a (in meters) and ellipsoid eccentricity squared e2.
[in] | a | semi-major axis |
[in] | e2 | ellipsoid eccentricity |
Definition at line 67 of file area_poly1.c.
Referenced by G_begin_polygon_area_calculations().
double G_ellipsoid_polygon_area | ( | const double * | lon, |
const double * | lat, | ||
int | n | ||
) |
Area of lat-long polygon.
Returns the area in square meters of the polygon described by the n pairs of lat,long vertices for latitude-longitude grids.
Note: This routine assumes grid lines on the connecting the vertices (as opposed to geodesics).
[in] | lon | array of longitudes |
[in] | lat | array of latitudes |
[in] | n | number of lat,lon pairs |
Definition at line 110 of file area_poly1.c.
References Radians, and TWOPI.
Referenced by G_area_of_polygon().