area_poly1.c File Reference

#include <math.h>
#include "gis.h"
#include "pi.h"

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Functions
int	G_begin_ellipsoid_polygon_area (double a, double e2)
	begin area calculations
double	G_ellipsoid_polygon_area (double *lon, double *lat, int n)
	area of lat-long polygon

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Function Documentation

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.

Parameters:

	a
	e2

Returns:

int

Definition at line 45 of file area_poly1.c.

References PI.

Referenced by G_begin_polygon_area_calculations().

double G_ellipsoid_polygon_area	(	double *	lon,
		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.)

Parameters:

	lon
	lat
	n

Returns:

double

Definition at line 88 of file area_poly1.c.

References PI, and Radians.

Referenced by G_area_of_polygon().

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