[mkgmap-dev] problem with splitter and bounding polygon

Sun Mar 6 06:37:16 GMT 2016

Hi Andrzej,

sure, if you change the poly you can avoid the situation. The problem
appears most likely when a highly populated area is close to, but outside of the poly 
and a lowly populated area inside and the polygon line is a long diagonal line at this place.

I'll see if I can improve the algo. 
I think as long as mkgmap doesn't support poly files we have to solve the problem in splitter.

On the other hand, a simple filter in mkgmap should also be possible. We already have 
UnusedElementsRemoverHook.java which magically detects elements in the input file
which will not appear in the output file. If we change this filter to check against a poly 
instead of a bbox it might be good enough. 
I only hesitate to implement that because one might expect that this woud also 
allow splitting maps at country borders, which requires much more work
when routing across these borders should work.

Gerd

________________________________________
Von: mkgmap-dev-bounces at lists.mkgmap.org.uk <mkgmap-dev-bounces at lists.mkgmap.org.uk> im Auftrag von Andrzej Popowski <popej at poczta.onet.pl>
Gesendet: Sonntag, 6. März 2016 02:00
An: mkgmap-dev at lists.mkgmap.org.uk
Betreff: Re: [mkgmap-dev] problem with splitter and bounding polygon

Hi Gerd,

> I don't yet have a solution, I just know that the current approach
> is not okay.

No easy solution. I think maybe the best would be to trim border tiles
according to bounding polygon. This could be suitable for irregular
tiles too.

Other idea could be to estimate full content of a tile on border, adding
a number of nodes proportional to area outside bounding polygon. This
won't be precise but I guess quite easy to implement.

In my case simplification of bounding polygon was sufficient to get
usable split.

--
Best regards,
Andrzej
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