New answers tagged topology
1
I've managed to solve this, without using the mentioned GRASS tools or topological functions.
Basically I take all start- and endnodes, put them in a new, temporary table, put a buffer around them, union the buffer objects, and move all found nodes in each buffer to the centroid of the buffer.
When that's done I move the original begin and end points to ...
1
Here are three options. Hopefully one will help.
v.clean
Using the GRASS tools in QGIS you can clean up the topology of a spatial object. User @R.K. gives a good set of instructions on how to do this in an answer to a different question. The advantage that GRASS gives is that it will infer the shapefile's topology. The disadvantage for your situation is ...
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PostGIS has snapping functions.. maybe they will help?
ST_Snap: Snap segments and vertices of input geometry to vertices of a reference geometry.
ST_SnapToGrid: Snap all points of the input geometry to a regular grid.
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Some GIS rather hide than show topological errors. In terms of GRASS GIS, you may want to check the related Wiki pages at http://grasswiki.osgeo.org/wiki/Topology . Note that the current GRASS GIS 7 development versions now makes suggestions for snap thresholds in order to assist the user to clean topological errors. Upon import it is also possible to write ...
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Refer to my answer at http://gis.stackexchange.com/a/59566/17606 it might help. Fully agree with gm70560's points!
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What do you use to extract contours from LiDAR data? Every how many meters are your contours?
If you start from a raster derived from the LiDAR data you could try to run a smoothing filter over the raster and then extract the contours: dangles and islands derive from sudden changes in heights (e.g.. sometimes outliers).
PS I know that running a smoothing ...
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My favorite saying from one of my professors is, "Garbage in, Garbage Out." No matter the algorithm or method used, there will be no "magic button" that will fix a crummy dataset. Sometimes, the tools will make the data less accurate. No errors, but incorrect.
Each project you will work on will have different requirements. I don't feel a quick map made ...
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To do this you need to perform a topological sort, where the triangles are
the nodes of the graph and the edge-adjacency provides the graph edges.
Since you know the graph is a single line, the sort actually devolves into
finding a node with only one other adjacent triangle, and then traversing
the graph visiting all the other triangles in turn.
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