NAME
v.clean - Toolset to clean vector topology.
SYNOPSIS
v.clean
v.clean help
v.clean [-b] input=string output=string [type=string[,string,...]] [err=string] tool=string[,string,...] [thresh=float[,float,...]]
Flags:
- -b
- Do not rebuild and store the topology at the end.
Parameters:
- input=string
- Name of input vector
- output=string
- Name of output vector
- type=string[,string,...]
- Type
- Options: point,line,boundary,centroid,area
- Default: point,line,boundary,centroid,area
- err=string
- Name of output map where errors are written.
- tool=string[,string,...]
- Cleaning tool
- Options: break,rmdupl,rmdangle,chdangle,rmbridge,chbridge,snap,rmdac,bpol,prune,rmarea,rmsa
- break: break lines at each intersection
- rmdupl: remove duplicate lines (pay attention to categories!)
- rmdangle: remove dangles, threshold ignored if < 0
- chdangle: change the type of boundary dangle to line, threshold ignored if < 0, input line type is ignored
- rmbridge: remove bridges connecting area and island or 2 islands
- chbridge: change the type of bridges connecting area and island or 2 islands from boundary to line
- snap: snap lines to vertex in threshold
- rmdac: remove duplicate area centroids ('type' option ignored)
- bpol: break (topologically clean) polygons (imported from non topological format (like shapefile). Boundaries are broken on each point shared between 2 and more polygons where angles of segments are different
- prune: remove vertices in threshold from lines and boundaries, boundary is pruned only if topology is not damaged (new intersection, changed attachement of centroid), first and last segment of the boundary is never changed
- rmarea: remove small areas, the longest boundary with adjacent area is removed
- rmsa: remove small angles between lines at nodes
- thresh=float[,float,...]
- Threshold
- Threshold in map units, one value for each tool (default: 0.0[,0.0,...])
DESCRIPTION
v.clean allows the user to automatically change (repair) vector files.
The user does not have to run v.build afterwards.
NOTES
What is a bridge?
A bridge is an area type connection of an island (polygon in a polygon) to the outer
polygon. This is topologically incorrect (but OGC Simple Features allow it). v.clean
can be used to optionally change the line type to fulfill the topology rules or to
remove the bridge from the map:
+-------------+ +-------------+ +-------------+
| P| P: polygon | P| | P|
| +---+ | I: island | +---+ | | +---+ |
| | I | | B: bridge | | I | | | | I | |
| | | | : line | | | | | | | |
| +-+-+ | | +---+ | | +-.-+ |
| | | | | | . |
| | B | | | | . L |
| | | | | | . |
+------+------+ +-------------+ +-------------+
EXAMPLES
Snap lines to vertex in threshold
v.clean input=testmap output=cleanmap tool=snap thresh=1
Cleaning OGR imported data (Simple Feature data)
The import of areas with v.in.ogr requires a subsequent run of
v.clean to update the map to a topologically
valid structure (removal of duplicate collinear lines etc). The tools
used for that are 'rmdupl' and 'bpol':
v.clean input=areamap output=areamap_clean tool=rmdupl,bpol
Extracting intersection points of vector lines
v.clean input=lines1 output=lines2 err=points tool=break
Intersection points are written to 'points' map.
AUTHOR
David Gerdes, U.S. Army Construction Engineering
Research Laboratory
Radim Blazek, ITC-Irst, Trento, Italy
Last changed: $Date: 2004/08/07 15:56:22 $
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