area_poly1.c File Reference

#include <math.h>
#include <grass/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


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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