[mkgmap-dev] problem routing across tiles again

Sun Sep 6 14:45:00 BST 2009

Hi Maning,

> I encountered routing across tiles again.
> Using mkgmap ver 1163 and splitter r83.
> 
> This photo shows routing detours to the cemetery when I used a split file:
> http://farm3.static.flickr.com/2593/3892530364_d80a7546b4_o.png
> 
> But no problems when no split file was used:
> http://farm3.static.flickr.com/2499/3891743809_21048450de_o.png

Hmm, yes, really tricky this one. The tile has been split at a point
that is close enough to a node that the resulting arc is of zero length
but the coordinates of the two nodes are not so close as to be
considered the same. If the split had actually been slightly closer to
the node on the left, I believe the routing would work as expected as
the split point and the left hand node would have had the same map
coordinates.

The issue here is that short arc removal is done before the tile's
bounding box is applied so it is possible for short arcs to be created
when the tile is clipped. A little while back I attempted to do the
clipping before the short arc removal but that had bad issues as well
so, at this time, I don't have a plan to solve this issue. Sorry.

What might work is if we can somehow tweak the arc to make it usable.

Can you please save the tile files so that if I (or anyone else, of
course) come up with a fix in the future, you could test it.

Cheers,

Mark