v4 I have gone back to the original ordering of doing short arc removal before clipping as the previous version of this patch badly broke polygons As for arcs whose length is less 5m, I am not convinced they are actually a problem as far as routing is concerned as my tests show that mapsource can happily route through zero length arcs that occur at tile boundaries. It would be good if people who have been obliged to use a minimum arc length of > 0 would provide examples of where the routing is broken. i.e. without using this patch, find an example which doesn't route when --remove-short-arcs is specified but will route when --remove-short-arcs=5 is specified. What is still an issue and was discussed a while ago is the problem where routing will fail (or produce a big diversion) when routing out of one tile into another and then back to a destination in the first tile. That never seems to work, short arcs or not. -------------------- v3 This patch is getting serious! To reduce the number of short arcs that are being generated at tile boundaries, this now clips the ways before the short arc removal is done. However, it isn't a perfect solution because some map data is very hard to deal with: a - If a way crosses a tile boundary right in the corner such that both ends are clipped and the resulting sub-way is less than 5m long, it will fail to fix that. A possible workaround could be to introduce extra points to elongate the arc. b - a much more common problem is where a way forks very close to a tile boundary and more than one of the connected ways cross the boundary so you end up with several boundary nodes that should be merged to remove the short arc(s) but they can't be moved as they are boundary nodes! I believe that this could be fixed by not merging the forking node but, instead, moving it away from the boundary such that the ways connected to it that do cross the boundary are not less than 5m long! Alternatively, adding extra points to elongate the forking arcs could be done. With this patch, I processed a 14 tile map of the Netherlands and it produced 21 of these short arc errors (all due to forks close to the tile boundaries). I then tested the routing at 5 of these positions (using mapsource) and only 1 of the 5 showed any sign of breakage, the other 4 all routed happily in all directions. The one that was broken was a junction of three ways and one pair of the ways had no connectivity but the others were ok. On the upside, the patch removed 147 short arcs introduced by the clipping. So more work is required here to fix the corner cases (ha ha) but please test this patch anyway as I expect it to have problems due to the big change it has introduced. As usual, all feedback is appreciated. ---------------- v2 of this patch not only enables remove-short-arcs by default when routing is in use (as previously discussed on ML) but it also fixes some problems in the way splitting code. I would be grateful if people could test this patch because it could possibly cure some routing failures. Cheers, Mark