[mkgmap-dev] merge-lines and routing

Mon Apr 29 20:54:52 BST 2013

>  >
>  > > Routing is completely broken if you change the source so that
> merging is
>  > > also
>  > > done for roads in res 24, so it must be handled with care,
>  >
>  > The LineMergeFilter does not care about routing nodes. That should be
>  > the reason why routing fails when using it at res 24.
>
> 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?

>
>  > Anyhow I did not yet fully understand about the relation of the routing
>  > network (NOD) to the map data at resolution 24. Are there any ids that
>  > are shared? When selecting a street how does the Garmin find the correct
>  > entry into the routing network?
>
> I wish I could say that I understand it :-O

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?
I think it's not bad to try to understand the different processing steps 
to see the big picture...