v.clean(1)

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 $

Help Index