gis/distance.c File Reference

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

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Functions
int	G_begin_distance_calculations (void)
	Begin distance calculations. More...
double	G_distance (double e1, double n1, double e2, double n2)
	Returns distance in meters. More...
double	G_distance_between_line_segments (double ax1, double ay1, double ax2, double ay2, double bx1, double by1, double bx2, double by2)
	Returns distance between two line segments in meters. More...
double	G_distance_point_to_line_segment (double xp, double yp, double x1, double y1, double x2, double y2)
	Returns distance between a point and line segment in meters. More...

Function Documentation

int G_begin_distance_calculations

(

void

)

Begin distance calculations.

Initializes the distance calculations. It is used both for the planimetric and latitude-longitude projections.

Returns

0 if projection has no metrix (ie. imagery)

1 if projection is planimetric

2 if projection is latitude-longitude

Definition at line 44 of file gis/distance.c.

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

Referenced by Gs_distance(), and Vect_line_geodesic_length().

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

Returns 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

[in]	e1,n1	east-north coordinates of first point
[in]	e2,n2	east-north coordinates of second point

Returns

distance

Definition at line 78 of file gis/distance.c.

References G_geodesic_distance().

Referenced by G_distance_point_to_line_segment(), and Gs_distance().

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

Returns distance between two line segments in meters.

Parameters

[in]	ax1,ay2,ax2,ay2	first segment
[in]	bx1,by2,bx2,by2	second segment

Returns

double

Definition at line 96 of file gis/distance.c.

References G_distance_point_to_line_segment(), G_intersect_line_segments(), and y.

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

Returns distance between a point and line segment in meters.

Parameters

[in]	xp,yp	point coordinates
[in]	x1,x1	segment point coordinates
[in]	x2,y2	segment point coordinates

Returns

distance

Definition at line 126 of file gis/distance.c.

References G_distance(), G_intersect_line_segments(), G_warning(), and y.

Referenced by G_distance_between_line_segments().