Vlib/snap.c File Reference

Vector library - Clean vector map (snap lines) More...

#include <stdlib.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <math.h>
#include <grass/vector.h>
#include <grass/glocale.h>
#include <grass/kdtree.h>

Include dependency graph for Vlib/snap.c:

Go to the source code of this file.

Macros
#define	X1W   0x01 /* x1 is West, x2 East */
#define	Y1S   0x02 /* y1 is South, y2 North */
#define	Z1B   0x04 /* z1 is Bottom, z2 Top */

Functions
void	Vect_snap_lines_list (struct Map_info *Map, const struct ilist *List_lines, double thresh, struct Map_info *Err)
	Snap selected lines to existing vertex in threshold. More...
void	Vect_snap_lines (struct Map_info *Map, int type, double thresh, struct Map_info *Err)
	Snap lines in vector map to existing vertex in threshold. More...
int	Vect_snap_line (struct Map_info *Map, struct ilist *reflist, struct line_pnts *Points, double thresh, int with_z, int *nsnapped, int *ncreated)
	Snap a line to reference lines in Map with threshold. More...

Detailed Description

Vector library - Clean vector map (snap lines)

Higher level functions for reading/writing/manipulating vectors.

(C) 2001-2009 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.

Author

Radim Blazek

update to GRASS 7 Markus Metz

Definition in file Vlib/snap.c.

Macro Definition Documentation

X1W

#define X1W   0x01 /* x1 is West, x2 East */

Definition at line 27 of file Vlib/snap.c.

Y1S

#define Y1S   0x02 /* y1 is South, y2 North */

Definition at line 28 of file Vlib/snap.c.

Z1B

#define Z1B   0x04 /* z1 is Bottom, z2 Top */

Definition at line 29 of file Vlib/snap.c.

Function Documentation

Vect_snap_line()

int Vect_snap_line	(	struct Map_info *	Map,
		struct ilist *	reflist,
		struct line_pnts *	Points,
		double	thresh,
		int	with_z,
		int *	nsnapped,
		int *	ncreated
	)

Snap a line to reference lines in Map with threshold.

3D snapping is supported. The line to snap and the reference lines can but do not need to be in different vector maps.

Vect_snap_line() uses less memory, but is slower than Vect_snap_lines_list()

For details on snapping, see Vect_snap_lines_list()

Parameters

[in]	Map	input map with reference lines
[in]	reflist	list of reference lines
[in,out]	Points	line points to snap
[in]	thresh	threshold in which to snap vertices
[in]	with_z	2D or 3D snapping
[in,out]	nsnapped	number of snapped vertices
[in,out]	ncreated	number of new vertices (on segments)

Returns

1 if line was changed, otherwise 0

Definition at line 961 of file Vlib/snap.c.

Vect_snap_lines()

void Vect_snap_lines	(	struct Map_info *	Map,
		int	type,
		double	thresh,
		struct Map_info *	Err
	)

Snap lines in vector map to existing vertex in threshold.

For details see Vect_snap_lines_list()

Parameters

[in]	Map	input map where vertices will be snapped
[in]	type	type of lines to snap
[in]	thresh	threshold in which snap vertices
[out]	Err	vector map where lines representing snap are written or NULL

Returns

void

Definition at line 907 of file Vlib/snap.c.

Vect_snap_lines_list()

void Vect_snap_lines_list	(	struct Map_info *	Map,
		const struct ilist *	List_lines,
		double	thresh,
		struct Map_info *	Err
	)

Snap selected lines to existing vertex in threshold.

Snap selected lines to existing vertices of other selected lines. 3D snapping is not supported.

Lines showing how vertices were snapped may be optionally written to error map. Input map must be opened on level 2 for update at least on GV_BUILD_BASE.

As mentioned above, lines are not necessarily snapped to nearest vertex! For example:

 |                    
 | 1         line 3 is snapped to line 1,
 |           then line 2 is not snapped to common node at lines 1 and 3,
 because it is already outside of threshold
 ----------- 3

 |
 | 2
 |    

The algorithm selects anchor vertices and snaps non-anchor vertices to these anchors. The distance between anchor vertices is always > threshold. If there is more than one anchor vertex within threshold around a non-anchor vertex, this vertex is snapped to the nearest anchor vertex within threshold.

Parameters

	Map	input map where vertices will be snapped
	List_lines	list of lines to snap
	thresh	threshold in which snap vertices
[out]	Err	vector map where lines representing snap are written or NULL

Returns

void

Definition at line 170 of file Vlib/snap.c.

References getenv().