New answers tagged topology
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 ...
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 ...
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.
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 ...
Refer to my answer at http://gis.stackexchange.com/a/59566/17606 it might help. Fully agree with gm70560's points!
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 ...
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 ...
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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