GIS Library - Geodesic distance routines. More...

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

Include dependency graph for geodist.c:

Functions
int	G_begin_geodesic_distance (double a, double e2)
	Begin geodesic distance. More...

int	G_set_geodesic_distance_lat1 (double lat1)
	Sets geodesic distance lat1. More...

int	G_set_geodesic_distance_lat2 (double lat2)
	Sets geodesic distance lat2. More...

double	G_geodesic_distance_lon_to_lon (double lon1, double lon2)
	Calculates geodesic distance. More...

double	G_geodesic_distance (double lon1, double lat1, double lon2, double lat2)
	Calculates geodesic distance. More...

Detailed Description

GIS Library - Geodesic distance routines.

Distance from point to point along a geodesic code from Paul D. Thomas, 1970
"Spheroidal Geodesics, Reference Systems, and Local Geometry"
U.S. Naval Oceanographic Office, p. 162
Engineering Library 526.3 T36s http://stinet.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=AD0703541

WARNING: this code is preliminary and may be changed, including calling sequences to any of the functions defined here.

This program is free software under the GNU General Public License (>=v2). Read the file COPYING that comes with GRASS for details.

Author: GRASS GIS Development Team

Date: 1999-2008

Definition in file geodist.c.

Function Documentation

int G_begin_geodesic_distance	(	double	a,
		double	e2
	)

Begin geodesic distance.

Initializes the distance calculations for the ellipsoid with semi-major axis a (in meters) and ellipsoid eccentricity squared e2. It is used only for the latitude-longitude projection.
Note: Must be called once to establish the ellipsoid.

Parameters

[in]	a	semi-major axis in meters
[in]	e2	ellipsoid eccentricity

Returns: always returns 0

Definition at line 52 of file geodist.c.

Referenced by G_begin_distance_calculations().

double G_geodesic_distance	(	double	lon1,
		double	lat1,
		double	lon2,
		double	lat2
	)

Calculates geodesic distance.

Calculates the geodesic distance from lon1,lat1 to lon2,lat2 in meters.
Note: The calculation of the geodesic distance is fairly costly.

Parameters

[in]	lon1,lat1	longitude,latitude of first point
[in]	lon2,lat2	longitude,latitude of second point

Returns: distance in meters

Definition at line 212 of file geodist.c.

References G_geodesic_distance_lon_to_lon(), G_set_geodesic_distance_lat1(), and G_set_geodesic_distance_lat2().

Referenced by G_distance(), and Vect_line_geodesic_length().

double G_geodesic_distance_lon_to_lon	(	double	lon1,
		double	lon2
	)

Calculates geodesic distance.

Calculates the geodesic distance from lon1,lat1 to lon2,lat2 in meters where lat1 was the latitude passed to G_set_geodesic_distance_latl() and lat2 was the latitude passed to G_set_geodesic_distance_lat2().

Parameters

[in]	lon1	first longitude
[in]	lon2	second longitude

Returns: double distance in meters

Definition at line 135 of file geodist.c.

References forms::q, Radians, and y.

Referenced by G_geodesic_distance().

int G_set_geodesic_distance_lat1 ( double lat1 )

Sets geodesic distance lat1.

Set the first latitude.

Note: Must be called first.

Parameters

[in] lat1 first latitude

Returns: always returns 0

Definition at line 75 of file geodist.c.

References Radians.

Referenced by G_geodesic_distance().

int G_set_geodesic_distance_lat2 ( double lat2 )

Sets geodesic distance lat2.

Set the second latitude.

Note: Must be called second.

Parameters

[in] lat2 second latitidue

Returns: always returns 0

Definition at line 94 of file geodist.c.

References Radians.

Referenced by G_geodesic_distance().

Functions

Detailed Description

Function Documentation