GRASS GIS 7 Programmer's Manual  7.5.svn(2018)-r72095
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area_sphere.c File Reference

GIS Library - Sphereical area calculation routines. More...

#include <math.h>
#include <grass/gis.h>
#include "pi.h"
Include dependency graph for area_sphere.c:

Go to the source code of this file.

Functions

void G_begin_zone_area_on_sphere (double r, double s)
 Initialize calculations for sphere. More...
 
double G_darea0_on_sphere (double lat)
 Calculates integral for area between two latitudes. More...
 
double G_area_for_zone_on_sphere (double north, double south)
 Calculates area between latitudes. More...
 

Detailed Description

GIS Library - Sphereical area calculation routines.

(C) 2001-2009 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.

Author
Original author CERL

Definition in file area_sphere.c.

Function Documentation

double G_area_for_zone_on_sphere ( double  north,
double  south 
)

Calculates area between latitudes.

This routine shows how to calculate area between two lats, but isn't efficient for row by row since G_darea0_on_sphere() will be called twice for the same lat, once as a south then again as a north.

Returns the area between latitudes north and south scaled by the factor s passed to G_begin_zone_area_on_sphere().

Parameters
north
[in]south
Returns
double

Definition at line 70 of file area_sphere.c.

References G_darea0_on_sphere().

void G_begin_zone_area_on_sphere ( double  r,
double  s 
)

Initialize calculations for sphere.

Initializes raster area calculations for a sphere. The radius of the sphere is r and s is a scale factor to allow for calculations of a part of the zone (see G_begin_zone_area_on_ellipsoid()).

Parameters
rradius of sphere
sscale factor

Definition at line 36 of file area_sphere.c.

References M_PI.

Referenced by G_begin_cell_area_calculations().

double G_darea0_on_sphere ( double  lat)

Calculates integral for area between two latitudes.

Parameters
latlatitude
Returns
area value

Definition at line 48 of file area_sphere.c.

References Radians.

Referenced by G_area_for_zone_on_sphere(), and G_begin_cell_area_calculations().