[mkgmap-dev] short arcs demystified, please try value 0From GerdP gpetermann_muenchen at hotmail.com on Sat Oct 5 10:56:06 BST 2013
Hi all, I think I understand now most of the miracles related to short arcs and I am pretty sure that we can solve the known problems without adding source complexity. 1) In 2009 Mark Burton added the remove-short-arcs option with r1049. 2) With r1060 he added the option to pass a parameter giving the minimum arc length to fix problems like "disappearing ways". Unfortunately, he missed the real reason for the error, which IMHO was the buggy implementation of --link-pois-to-ways and --remove-short-arcs regarding the highway count causing more or less unpredictable results. 3) For four years people wondered what value to use as a change of the value was likely to "fix" a known routing error while also adding other "not yet known" errors. Today I've committed r2736. I my eyes (presuming all coding errors are fixed now) the only usable value is --remove-short-arcs=0, everything else is likely to create problems like distorted lines, wrong routing (cars routed through footways) and wrong exit hints in roundabouts. The only advantage that I see is a slightly smaller number of nodes, but this will soon be fixed when the mergeroads branch is merged to trunk, but I might have missed something. So, in short: All those that are using mkgmap to create routable maps, please try r2736 with --remove-short-arcs=0 (binary is here http://files.mkgmap.org.uk/download/152/mkgmap.jar) or use the mergeroads branch (requires style changes) If you find any problem regarding routing, please let us know and try to provide details. If I hear no complains until Oct 15, I like to change the default back to 0 and print a warning if a different value is used. If --remove-short-arcs=0 works fine for everybody, we should remove the option. Gerd -- View this message in context: http://gis.19327.n5.nabble.com/short-arcs-demystified-please-try-value-0-tp5780224.html Sent from the Mkgmap Development mailing list archive at Nabble.com.
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