R: [mkgmap-dev] (almost) duplicated node issue

Sun May 24 21:49:36 BST 2009

I know about IMG resolution, Mark. That is the reason I think there is a bug. If the Garmin cannot handle such short arcs, mkgmap shall compile the case in a way that does not violate the garmin specs.

But I'm not really sure that the problem is exactly this. It might be that mkgmap has a bug in the routing data base compiling. Well I'm not expert, but I guess something goes wrong when the 2 so close nodes collapses in a single node when the garmin encoding is applied. Then 2 nodes in OSM, 1 node in Garmin... and the routing DB gets corrupted. Something like that (but I'm really speculating).

Someone should check the code to track the situation. The osm file I've attached (that reproduce the error) is small enough to be tested carefully.

Ciao.

--- Dom 24/5/09, Mark Burton <markb at ordern.com> ha scritto:

> Da: Mark Burton <markb at ordern.com>
> Oggetto: Re: R: [mkgmap-dev] (almost) duplicated node issue
> A: mkgmap-dev at lists.mkgmap.org.uk
> Data: Domenica 24 maggio 2009, 19:04
> 
> Hi Marco,
> 
> I believe that the distance between nodes must not be less
> than some
> minimum value (can't remember what it is off the top of my
> head). So I
> guess what you have found is an arc whose length is too
> short to
> handled by the garmin software.
> 
> Cheers,
> 
> Mark
> 
> > Well, maybe I've found something strange.
> > 
> > I've attached to this mail a .zip file containing a
> small .osm DB (downloaded today) and a screenshot (.png)
> > 
> > If I try to compile the attached .osm file, I get a
> map with broken routing data that crashes MapSource (for
> example try to get a route from one side to the other of
> "Piazza Caprera" in the centre of the map, or try routes in
> the lower left corner). This problem is independent by
> mkgmap style and mkgmap version (if you download the Italian
> map from http://www.team-oid.de/cgi-bin/maps_download/showdir.cgi
> compiled about one month ago, you'll get the same routing
> problems in this area)
> > 
> > I've discovered an issue that maybe is the cause of
> the problem. If you open the attached picture you'll see a
> very short segment (less than 1 meter) that you can identify
> with the coordinates. It is at the cross between Via Zara
> and Corso Trieste (you must zoom a lot).
> > 
> > Well, if you delete this short piece of road, the
> routing Data Base is built correctly by mkgmap. Maybe
> somthing related to rounding makes this too short segment a
> problem during map compiling (the two ends collapses in one
> point...).
> > 
> > I don't think I'll be able to go further: I hope that
> what I found can help some mkgmap developers to individuate
> the issue and a possible solution.
> > 
> > I've not corrected the OSM DB, so you can still
> download this area by yourself.
> > 
> > Ciao, Marco.
> > 
> > 
> > 
> >       
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