area_ellipse.c File Reference

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

Include dependency graph for area_ellipse.c:

Go to the source code of this file.

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


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().


Generated on Sun Apr 6 17:32:14 2008 for GRASS by  doxygen 1.5.5