[mkgmap-dev] [PATCH v1] - fix routing problems caused by way's bbox being too large

Tue Nov 3 09:52:48 GMT 2009


Mark Burton wrote:
> Ok, I think I know what's been going wrong with some people's maps
> where the routing goes zig-zaggy when the way is longish. However, it's
> not the number of points in the way or even the length of the way that's
> wrong.
>
> It's because the bounding box becomes sufficiently large that it causes
> the line to be split by the LineSizeSplitterFilter. This ancient
> bit of code splits the line so that it doesn't have a bigger bounding
> box than it thinks is acceptable. Well, that may be OK for plain lines
> but for routable stuff like roads, it's bad news because there's no node
> between the two parts of the split line. If, by chance, the point at
> where the way was split was actually a node anyway, it probably worked
> OK but for other points, anything could happen!
>
> So the attached patch checks the way's bounding box earlier on when
> it's doing all that boring way size/arc size/node count checking and if
> the BB gets too large it snips the way in the accustomed fashion.
>
> Anyway, please try the attached patch and see if it works OK - (no new
> bad routing, no assertions, etc.)
>
> Bloody hell, another long evening spent hacking mkgmap...
>   
thanks for your effort, with this patch applied I get identical routing 
to rev 1337 (while >1338 routing got worse)
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