GIS Library - Rhumbline calculation routines. More...

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

Include dependency graph for rhumbline.c:

Functions
int	G_begin_rhumbline_equation (double lon1, double lat1, double lon2, double lat2)
	Start rhumbline calculations.

double	G_rhumbline_lat_from_lon (double lon)
	Calculates rhumbline latitude.

Detailed Description

GIS Library - Rhumbline calculation routines.

From "Map Projections" by Peter Richardus and Ron K. Alder, 1972
(526.8 R39m in Map & Geography Library)
Page 20,21, formulas 2.21, 2.22

Formula is the equation of a rhumbline from (lat1,lon1) to (lat2,lon2). Input is lon, output is lat (all in degrees).

Note: Formula only works if 0 < abs(lon2-lon1) < 180. If lon1 == lon2 then rhumbline is the merdian lon1 (and the formula will fail).
WARNING: This code is preliminary. It may not even be correct.

SPDX-FileCopyrightText: 2001-2014 GRASS Development Team SPDX-License-Identifier: GPL-2.0-or-later

Author: GRASS Development Team

Date: 1999-2014

Definition in file rhumbline.c.

Function Documentation

◆ G_begin_rhumbline_equation()

int G_begin_rhumbline_equation	(	double	lon1,
		double	lat1,
		double	lon2,
		double	lat2
	)

Start rhumbline calculations.

Note: This function must be called before other rhumbline functions to initialize parameters.

Parameters

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

Returns: 1 on success; 0 on error

Definition at line 55 of file rhumbline.c.

References M_PI_4, Radians, and st.

◆ G_rhumbline_lat_from_lon()

double G_rhumbline_lat_from_lon ( double lon )

Calculates rhumbline latitude.

Note: Function only works if lon1 < lon < lon2.

Parameters

[in] lon longitude

Returns: double latitude in degrees

Definition at line 93 of file rhumbline.c.

References Degrees, M_PI_2, Radians, and st.

Functions

Detailed Description

Function Documentation

◆ G_begin_rhumbline_equation()

◆ G_rhumbline_lat_from_lon()