[mkgmap-dev] LocationHook and tagging waysFrom Gerd Petermann gpetermann_muenchen at hotmail.com on Wed Jan 11 08:31:47 GMT 2012
Hi WanMil, > Date: Tue, 10 Jan 2012 22:25:29 +0100 > From: wmgcnfg at web.de > To: mkgmap-dev at lists.mkgmap.org.uk > Subject: Re: [mkgmap-dev] LocationHook and tagging ways > > > Hi list, > > > > as discussed before, the current implementation of LocationHook produces > > somehow unpredictable results when it locates ways that cross boundaries. > > A correct solution would be to split the way, but according to WanMil this > > would be very slow. > > I think so. But of course it would be good to try that. Maybe it's also > possible to differ between a quick mode (the one which is implemented) > and an exact mode (splitting ways and shapes at the boundaries). I did not look at this until now, but I agree that it would result in higher quality. We already seem to have a class for that stuff, see AreaClipper which is used in StyledConverter, and LineClipper which is used in ElementSaver. Maybe we just have to move some method calls? > > > So, with bad luck, we may find a way with 100 points in a boundary that > > contains only one of them. > > > > While thinking about a test for my optimized version I wondered why we put > > all points of a way into the quadtree, and not only one (e.g. the 1st, the > > last, or the one in the middle). > > Using only one point makes the quadtree much smaller and faster, and the > > result is (almost) as correct as before. > > I see only one problem: If the way crosses boundaries, one of the boundaries > > may contain better information (more complete) than the other(s). If we > > chose the "wrong" point for searching, we may find only the incomplete > > information. > > That's the problem. In areas where boundaries are not 100% complete a > lot of elements are not assigned. Oh oh! I did not notice that until now. I thought it is a rare case that Node or Way is not found, because I only looked at the final result of LocationHook. I thought I can ignore the few cases where the first point of a way is not found. In fact, for some admin_levels we only have a few boundaries which do not nearly cover the whole bounding box, means, many ways are not found. This means my current implementation is much slower than expected :-(( and I definetly have to change it so that I have all boundary info in my quadtree before starting to seach. The good news is that I now have an idea how that could be done in the BoundaryPreparer. Ciao, Gerd -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.mkgmap.org.uk/pipermail/mkgmap-dev/attachments/20120111/e7a652d6/attachment.html
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