man v.clean () - Toolset to clean vector topology.


v.clean - Toolset to clean vector topology.



v.clean help

v.clean [-b] input=string output=string [type=string[,string,...]] [err=string] tool=string[,string,...] [thresh=float[,float,...]]


Do not rebuild and store the topology at the end.


Name of input vector
Name of output vector
Type Options: point,line,boundary,centroid,area Default: point,line,boundary,centroid,area
Name of output map where errors are written.
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
Threshold Threshold in map units, one value for each tool (default: 0.0[,0.0,...])


v.clean allows the user to automatically change (repair) vector files. The user does not have to run afterwards.


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 |

| | | | | | . |

+------+------+ +-------------+ +-------------+


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 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.


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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