NAME

v.clean - Break lines at intersections.

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
Select type: point, line, boundary, centroid or area
Options: point,line,boundary,centroid,area
Default: point,line,boundary,centroid,area
err=string
Name of output map where errors are written.
tool=string
Action to be done:
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 (topologicaly 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
Options: break,rmdupl,rmdangle,chdangle,rmbridge,chbridge,snap,rmdac,bpol
thresh=float
Threshold in map units for each tool (default: 0.0).

DESCRIPTION

v.clean allows the user to automatically change (repair) vector files. Possible tools are:

break
breaks lines and sets a node at each intersection

rmdupl
removes duplicate lines (pay attention to categories!)

snap
snaps vertex to a line and create new vertex at that line

rmdac
removes duplicate area centroids ('type' option ignored)

You do not have to run v.build 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    |
    |      |      |             |             |   |      .      |
    +------+------+             +-------------+   +-------------+

EXAMPLE

v.clean input=testmap output=cleanmap tool=svtlx breakthresh=1

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

AUTHOR

David Gerdes, U.S. Army Construction Engineering Research Laboratory
Radim Blazek, ITC-Irst, Trento, Italy

Last changed: $Date: 2004/03/10 13:26:14 $


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