Center for Spatial Information Science and Systems (CSISS)
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This service could be used to clean the topology of GRASS vector data.


clean_topology - Allows the user to automatically fix vector topology.

Request Parameters:

URL of input vector map
Default format: GML
Cleaning tool
Parameter format: string[,string,...]
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

Response Parameters:

URL of output vector map
Format of output vector map
Default : GML

For further informations


See also GRASS command


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