Chao YUE, This is probably not exactly what you want, but I wanted to mention that ogr2ogr in latest GDAL master has now received a -makevalid switch that relies on GEOSMakeValid() method of GEOS 3.8.0 or later (which itself is the port of PostGIS ST_MakeValid() to GEOS).
For people using the SQL SQLite dialect, ST_MakeValid() is also now available (still with GEOS >= 3.8), even against a Spatialite build that doesn't link against liblwgeom Even > Dear all, > > Does anyone have some experience or is aware of some algorithm that can > find and clip the inner loop formed in a polygon ? I attach one example > here. In this case I would only keep the outer points and drop the ones > that make an inner loop. I am developing some algorithm to simulate > wildland fire propagation. The algorithm is based on Richards 1990. > > In the paper he described an algorithm based on two steps: (1) find the > points where a concave curvature is made. (2) search for both sides of this > point to see where any two line segments cross over each other. > But I am wondering whether there is already some existing solutions or > other better ones. > > Thanks a lot for the kind help for any hints on this ! > Kind regards, > Chao > > Gwynfor Richards, 1990. An elliptical growth model of forest fire fronts > and its numerical solution. International journal for Numerical Methods in > Engineering, Vol. 30, 1163-1179. > > [image: InnerLoop.png] -- Spatialys - Geospatial professional services http://www.spatialys.com
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