[mkgmap-dev] merge-lines and routing

Mon Apr 29 21:13:17 BST 2013

> > yes, but not the only one. I created a version that made sure to split
> > roads so that they start and end with coordNode, but that (alone) did not
> > help.
> 
> Do you mean the LineMergeFilter or the LineSplitterFilter?

While testing I changed the code so that merge-lines was applied to roads 
also on res 24. As a result you get e.g. one MapRoad containing all points of
the original OSM way. This is passed through the filters and
LineSplitterFilter will cut it into peaces of < 250 points without looking
at coordNodes.
So I changed LineSplitterFilter to split only at coordNodes.

> Let's have a look on the processing in mkgmap:
> 
> 1. The StyledConverter applies the style to the Way object. This creates 
> a MapRoad object.
> 2. The MapRoad object is added to the RoadNetwork
> 3. The MapRoad object is passed through the filters. Some of these 
> filters may not care about routing nodes (CoordNode). But filters 
> usually copy the MapRoad object before modifying it.
> 4. After all filters have been applied the RoadNetwork is generated.
> 
> Do you think my short algo desription is correct?
Yes, I think that's what happens.

> I think it's not bad to try to understand the different processing steps 
> to see the big picture...
The next interesting part is that a RoadDef instance should collect parts of 
a road on different resolutions. In r2584 the program flow never allows
that more than one segment is collected at one resolution, but RoadDef 
is implemented to do that. With my changes these dead code parts were
reached (again), but routing did no longer work (not at all).
So, I assume that the routines which build the network are wrong.
I'll try to trace that down tomorrow.

Gerd

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