GRASS Programmer's Manual 6.4.1(2011)
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GIS Library - Rhumbline calculation routines. More...
Go to the source code of this file.
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. | |
Variables | |
static double | TAN1 |
static double | TAN2 |
static double | L |
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.
(C) 2001-2008 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.
Definition in file rhumbline.c.
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.
[in] | lon1,lat1 | longitude, latitude of first point |
[in] | lon2,lat2 | longitude, latitude of second point |
Definition at line 57 of file rhumbline.c.
double G_rhumbline_lat_from_lon | ( | double | lon | ) |
double L |
Definition at line 41 of file rhumbline.c.
Referenced by G__lookup_colors(), G__read_Cell_head(), G__write_row_ptrs(), G_begin_rhumbline_equation(), G_fopen_append(), G_fopen_append_misc(), G_fopen_modify(), G_fopen_modify_misc(), G_open_update(), G_open_update_misc(), G_plot_area(), G_plot_polygon(), G_put_reclass(), G_rhumbline_lat_from_lon(), and G_row_update_fp_range().
double TAN1 |
Definition at line 41 of file rhumbline.c.
Referenced by G_begin_rhumbline_equation(), and G_rhumbline_lat_from_lon().
double TAN2 |
Definition at line 41 of file rhumbline.c.
Referenced by G_begin_rhumbline_equation().