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[mkgmap-dev] mkgmap creates polygons that break Mapsource panning and also routing in some zoomlevels as well as crashing the GPS

From Felix Hartmann extremecarver at googlemail.com on Sat Sep 5 20:36:48 BST 2009

Mark Burton wrote:
> Felix,
> Wild guess here: I wondered if the POI index was overflowing and
> trashing some other stuff because in the bad map example you sent, it
> contained just over 32K entries. So commit 1170 disables POI index
> generation. It wasn't useful anyway, so that's no loss. Please see if
> that makes any difference.
> Mark
> _______________________________________________
> mkgmap-dev mailing list
> mkgmap-dev at lists.mkgmap.org.uk
> http://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev
thanks for your work,

by now I am sure (100%) which polygon was fucking up (as so far as being 
the main cause). It's the forest here: 
I have attached a screenshot of it' rendering in Mapsource.
If you set detail level to lowest, decrease the mapsource window size 
(e.g. to 240x240 pixels only), and then pan to it, you will notice that 
you can still display it partly, but near to the center will crash.

It was (I corrected it) connected at around 30 places to streets. On top 
of it sometimes lines were parallel in order to draw holes into the 
forest, so the intent here must have been to not show it at certain places.

Even though this is bad tagging practice, mkgmap should not create maps 
that send gps into rebot/crash, and also send mapsource 6.13.7 and 
before into big problems.
I am sure it was not the POI index overflowing, but has to do with nodes 
shared between streets and polygon.

I have no clue why Mapsource suffocates on that forest if streets are 
attached to it in osm database. Excluding rendering of the streets that 
shared nodes with the forest would have the same effect as not rendering 
the forest at all or skipping rendering another forest that was partly 
overlaying at the same place.

Well maybe you can still find out, Find in the new download:
1. Again the osm tile (I do hope my edits mean that tomorrow it will 
render without problems (disconnected all streets and administrative 
boarders, and corrected some of the nearly parallel lines).
2. not working with areas-pois
3. not working without without areas-pois
4. working excluding any rendering of wood=mixed & fixme=* and excluding 
landuse=forest & fixme=*, with areas-pois
2-4 consisting of tile plus log.

Get files for analysis (35MB) here: 

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