Clinton Gladstone <clinton.gladstone@googlemail.com> writes:
On Fri, Aug 14, 2009 at 2:44 PM, Greg Troxel<gdt@ir.bbn.com> wrote:
I most recently built with all 6 NE states (conn, ri, mass, vermont, new hampshire, maine) all together, invoking the script 'do-mkgmap' which follows as something like
$ do-mkgmap *.osm.bz2
In this case, routing will not work across state boundaries. You know that though, right?
No, I didn't know that. But now that I think about, I think I can see why. Is the issue that the extracts are split with polygons and osmosis, and there is no overlap and synthetic nodes at the boundary? I wonder if the polygons overlapped enough to make sure that there was a node in common, if that would make things work. But that's almost certainly not the big issue - if I can get to where intrastate routing works in each state that would be great.
I compiled Massachusetts and experimented with routing in Mapsource (I will try Roadtrip later). I found that routing only works for very short distances (even without crossing tile boundaries). For example, I tried the I95 around Boston. There, I could only route along segments which were less than 1 km long.
I'll take a look, and also try shorter routes not on the motorways. MassGIS data has the one-way property but not the direction. I've straightened out a lot of 495 and 2 but not I95 (=MA128). So motorways are particularly likely to be trouble, compared to normal state highways or regular roads.
It seemed, although I have not tested enough to confirm, that it was hardest routing along the more curved sections of highway. This would support the hypothesis that the node density is too high for proper routing. I have not had time to download the OSM data to take a look. I wonder if a way simplification patch could help here.
I suppose I could run --remove-short-arcs with 20m. Or a new option that drops nodes within 50m as long as they only have 2 arcs and the resulting position of the midpoint doesn't move by more than 2m, or something like that.
I'm surprised that you were able to create routable maps using --max-nodes=1600000. I had to lower max nodes to 800000 in order to compile.
I didn't realize that 1600000 was too big. My machine has 4G ram with a heapsize of 2G. Is it safe to assume that if it completes without error that things fit? In Mass I think the ratio of nodes to ways is much higher than in other places, so perhaps that explains it. Thanks very much for looking into this - now I'm pretty sure that I'm not doing something dumb, and that digging into it more is sensible.