GRASS Programmer's Manual  6.5.svn(2014)-r66266
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gis/distance.c File Reference
#include <math.h>
#include <grass/gis.h>
#include <grass/glocale.h>
Include dependency graph for gis/distance.c:

Go to the source code of this file.


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.

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.

[in]e1,n1east-north coordinates of first point
[in]e2,n2east-north coordinates of second point

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.

[in]ax1,ay2,ax2,ay2first segment
[in]bx1,by2,bx2,by2second segment

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.

[in]xp,yppoint coordinates
[in]x1,x1segment point coordinates
[in]x2,y2segment point coordinates

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().