[mkgmap-dev] Subdivision split problem (was: How to solve/debug weird problem)

Sun Jan 23 13:11:43 GMT 2011

>>
>> Now I can reproduce your problem!
>> Using your tile and your parameters I get the same exception. I'll have
>> to do some debugging session to see where the origin of the problem is.
>>
>> WanMil
>
> I have opened the tile with JOSM and there seem to be tons of bad
> polygons in it. The selected rel polygon is the way 92916925 and should
> look like http://www.openstreetmap.org/browse/way/92916925.
> So no matter if mkgmap behaves correct the maps generated from such
> tiles will not be the ones you like to have. Please have a look how you
> split the tiles.
>
> I will continue to check why mkgmap throws the exception.
>
> WanMil
>

Hi,

I think this is an old problem which has been discussed in Nov 2009. In 
commit r1392 
(http://www.mkgmap.org.uk/pipermail/mkgmap-dev/2009q4/005446.html) Mark 
Burton disabled some checks if lines and shapes are within the 
subdivision bounds. He noted "Sorry, I just don't have the capacity at 
the moment to work on a real solution to this thorny problem.". Ok, I 
think no one else did it so far...

The thread to this commit is 
http://www.mkgmap.org.uk/pipermail/mkgmap-dev/2009q4/005425.html.

As far as I understand the problem is that the Subdivisions are split to 
an appropriate size. If a line is located within the subdivision (which 
means its center point is in the subdivision) it is not ensured that all 
points are within the maximum coverable area size. If one point is far 
away from its center the maximum coverable range (which depends on zoom 
level) may exhausted.

Steve: Did you know about this?

WanMil