area_ellipse.c File Reference

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

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Functions
int	G_begin_zone_area_on_ellipsoid (double a, double e2, double s)
	begin area calculations for ellipsoid
double	G_darea0_on_ellipsoid (register double lat)
double	G_area_for_zone_on_ellipsoid (register double north, register double south)
	area between latitudes

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Function Documentation

double G_area_for_zone_on_ellipsoid	(	register double	north,
		register double	south
	)

area between latitudes

Returns the area between latitudes north and south scaled by the factor s passed to G_begin_zone_area_on_ellipsoid.

Parameters:

	north
	south

Returns:

double

Definition at line 70 of file area_ellipse.c.

References G_darea0_on_ellipsoid().

int G_begin_zone_area_on_ellipsoid	(	double	a,
		double	e2,
		double	s
	)

begin area calculations for ellipsoid

Initializes raster area calculations for an ellipsoid, where a is the semi-major axis of the ellipse (in meters), e2 is the ellipsoid eccentricity squared, and s is a scale factor to allow for calculations of part of the zone (s=1.0 is full zone, s=0.5 is half the zone, and s=360/ew_res is for a single grid cell). Note. e2 must be positive. A negative value makes no sense, and zero implies a sphere.

Parameters:

	a
	e2
	s

Returns:

int

Definition at line 31 of file area_ellipse.c.

References PI, and sqrt().

Referenced by G_begin_cell_area_calculations().

double G_darea0_on_ellipsoid

(

register double

lat

)

Definition at line 43 of file area_ellipse.c.

References Radians, and sin().

Referenced by G_area_for_zone_on_ellipsoid(), and G_begin_cell_area_calculations().

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