I am looking for a method from Grass, GEOS, or similar that will delete those points in a geometry which do not affect its shape.

Example 1

p0   p1   p2

p1 can be deleted without affecting the shape of the line

Example 2

   p0   p1
   |     \
p4 +      \
   |       \
p3 +--------+ p2   

p4 can be deleted without affecting the shape of the polygon

I am sure this has been asked/answered and there is probably a name for the output point set (akin to convex hull) but I am not sure what to search for.

It would be relatively straightforward (no pun intended) to write my own function but obviously silly if there is something out there already.

  • 4
    A simple Ramer-Douglas-Peucker with a very small tolerance will eliminate redundant vertices – Vince Dec 10 '15 at 14:29
  • The "generalize" or "simplify" tools of most GIS packages use RDP (previously known as Douglas-Peucker or Douglas-Poiker) see also gis.stackexchange.com/questions/25914/… – Vince Dec 10 '15 at 16:44

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