>
>>> I have found some glitches with multipolygons however, but I dont
>>> know if it is related to the patch or an existing problem.
>>
>> Right, my fix doesn't target multipolygons at all. I tried lakes in
>> Finland, and I saw multipolygon breakage as expected, although some
>> improvements too.
>
>
> Ah ok,
>
> Here is another smaller example:
>
> This drain http://www.openstreetmap.org/browse/way/69701523
> is part of a landuse=residential mp 
> http://www.openstreetmap.org/browse/relation/1100932
>
> If I render only waterways, not residential areas, it puts a drain around the 
> whole mp.

Good catch! This has nothing to do with Steves patch.
To save memory mkgmap loads only those tags that are referenced in the 
style file.

You have:
mp 1100932: landuse = residential
  way 69701523: waterway = drain
  way 69701491: waterway = drain
  way 68635609: <no tags>
  way 69701470: <no tags>

If you have no rule with landuse but a rule with waterway mkgmap loads 
the following:
mp 1100932: <no tag>
  way 69701523: waterway = drain
  way 69701491: waterway = drain
  way 68635609: <no tags>
  way 69701470: <no tags>

The mp algorithm thinks that the mp is not tagged. So it collects the 
tags from the outer ways => waterway=drain (outer ways without tags are 
ignored here. I don't remember why - maybe this should be corrected).

So you get a line around your residentail area tagged with waterway=drain.


What can we do to avoid such a problem?
For multipolygons the loader should not throw away any tag - no matter 
if it is used or not. Otherwise it is not possible for the mp algorithm 
to avoid such a problem for sure. The memory penalty should not be so 
bad because the number of multipolygons is not so big in each tile.


> Even if I don't put waterways in my polygon style at all. So this might be a 
> glitch in the mp processing too?

I assume you have rules in your lines file for waterways?

WanMil




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