[mkgmap-dev] [PATCH v1] - Sub-optimal fix to limit excessive inter-node arc length

Thu Apr 16 11:34:26 BST 2009

Folks,

The attached patch tries to limit the inter-node arc length to less
than 14 bits so that it doesn't get truncated in RouteArc. This appears
to fix the problems that have been reported by myself and others.

Specifically, if you have a road that has large distances between the
nodes, this patch should help if you are having problems routing.

The patch is a hack because the real fix would be to make
encodeLength() cope with lengths that require more than 14 bits but I
don't really have time to look into that. It may be trivial, perhaps
the original author could look at it again?

Also, there will be a performance penalty in using this patch because
it calculates the arc lengths again which is quite an expensive
operation (lots of sums).

So, if you are seeing routing issues, it may be worth applying this
patch until the arc length encoding is fixed. I have tried a few maps
with the patch and some do report arc length fixes.

The patch also adds a couple of assertions to catch a special case in
the polyline encoding which we don't currently explicitly handle.

Cheers,

Mark
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