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[mkgmap-dev] Testing routing

From Steve Ratcliffe steve at parabola.demon.co.uk on Sun Dec 7 14:11:33 GMT 2008


I've had lots of fun trying the routing out.

I've tried with a fairly large London extracts and it is very good at
making routes in most places when zoomed in, but I get a crash (program
exits) when zooming out in mapsource.

In general I can build up reasonably large routes, but sometimes I get a
failure dialog when it fails to find a route.  The failing to find a route
seemed to happen more often when I was at the edge of the map, although
that may be a coincidence.

When it fails to find a route I can usually help it by picking an
intermediate point first, and getting to the point I was aiming
in a series of steps.

Sometimes though it is just imposible to get past a particular point.
I've noticed that on the edge of such an area, there are sometimes routes
that go back and forward on the same road.

I guess we need to know where the problem is and distinguish between the

1. Problems with the tagging or topology of the OSM data itself.
2. Problems with extracting the routing network from the OSM data.
3. Problems with the incorrect .img format being generated.

I plan to start with a small area, chose a single starting point and plot
out all the places that can and can't be reached from there.  Then look
at the file in josm and see if there is anything funny about the data and
if fixing it makes the problem change.


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