distance.c File Reference

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

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Functions
int	G_begin_distance_calculations ()
	begin distance calculations
double	G_distance (double e1, double n1, double e2, double n2)
	distance in meters
double	G_distance_between_line_segments (double ax1, double ay1, double ax2, double ay2, double bx1, double by1, double bx2, double by2)
double	G_distance_point_to_line_segment (double xp, double yp, double x1, double y1, double x2, double y2)

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Function Documentation

int G_begin_distance_calculations

(

)

begin distance calculations

Initializes the distance calculations. It is used both for the planimetric and latitude-longitude projections. It returns 2 if the projection is latitude-longitude, 1 if the projection is planimetric, and 0 if the projection doesn't hav e a metric (e.g. imagery.)

Parameters:

void

Returns:

int

Definition at line 28 of file distance.c.

References G_begin_geodesic_distance(), G_database_units_to_meters_factor(), G_get_ellipsoid_parameters(), and G_projection().

double G_distance	(	double	e1,
		double	n1,
		double	e2,
		double	n2
	)

distance in meters

This routine computes the distance, in meters, from x1,y1 to x2,y2. If the projection is latitude-longitude, this distance is measured along the geodesic. Two routines perform geodesic distance calculations.

Parameters:

	x1
	y1
	x2
	y2

Returns:

double

Definition at line 66 of file distance.c.

References G_geodesic_distance().

Referenced by G_distance_point_to_line_segment().

double G_distance_between_line_segments	(	double	ax1,
		double	ay1,
		double	ax2,
		double	ay2,
		double	bx1,
		double	by1,
		double	bx2,
		double	by2
	)

Definition at line 77 of file distance.c.

References G_distance_point_to_line_segment(), and G_intersect_line_segments().

double G_distance_point_to_line_segment	(	double	xp,
		double	yp,
		double	x1,
		double	y1,
		double	x2,
		double	y2
	)

Definition at line 100 of file distance.c.

References G_distance(), and G_intersect_line_segments().

Referenced by G_distance_between_line_segments().