[mkgmap-dev] trouble routing across extracts

Sat Jan 14 01:08:16 GMT 2012

I am not saying it can't work. But fact is that the extracts don't align always and there are different cut algorithms. Some keep the whole way, others drop nodes outside the cut polygon and the last even drops the reference to the node in the way. so yes merging can work if all data is kept and merged correct. But how can you ever be sure all connections are kept?

If you know what you are doing and understand the possible failures then it's fine. But if someone claims there is a bug or a broken tool chain then this is just wasted time. and again this has been discussed to dead already.

On Jan 13, 2012, at 3:25 PM, Greg Troxel wrote:

> 
> This combinining-extracts approach used to work for me.  I used
> cloudmade state extracts (back when they were updated regularly).  My
> understanding was that the extracts had enough data beyond the
> boundaries so that when neighboring extracts were fed to splitter one
> ended up with connected ways.  Then, after a lull in map building, I
> used geofabrik state extracts and found that I couldn't route across
> state lines.
> 
> Certainly I can see that this won't work in general if there isn't a
> node across the line in one or the other extracts so that the resulting
> union of datasets isn't connected.  But if the union is connected, it
> seems that routing should work.
> 
> (And, I believe that people have added near-state-line nodes in some
> cases to make the state-union routing work.  My point is that even if
> it's theoretically impossible for the scheme to be correct, it can work
> well enough to be highly useful.)
> 
> My desire to use state extracts stems from wanting to update
> massachusetts much more frequently than others -- or whatever states I'm
> about to be in, but still build new england maps.   While I could use
> us-northeast, that puts more load on Frederik's server, and there is no
> solution for the region boundaries.
> 
> 
> So are you saying  that the geofabrik extracts don't contain any nodes
> across the borders?  Do the ways (that in fact cross the borders) then
> stop short of the border?   How did this used to work with cloudmade
> extracts?