[mkgmap-dev] rendering nested relations

Fri Dec 7 14:58:08 GMT 2012

> 
> It's a question of parsing the data.
> 
> You (means mkgmap) have to rebuild superroutes, till there are only 
> way-member in it.
> 
> Eg:
> parse tile and read all relation (maybe store in RAM)
> if relation_A contains relations_B, replace all relations_B in this 
> relation_A  with the objects the relation_B1...Bn  contain.
> end, if no relation contains any relation.
> 
> This shouldn't be very complex and not very expensive, because there are 
> typical not so many relation in one tile.
> 

Yes, but mkgmap must make sure that it handles the case when relations are building loops:
Examples:
rel_a contains rel_b, rel_b contains rel_a
or, a bit more complex:
rel_a -> rel_b -> rel_c -> rel_d->rel_b

some time ago I found a relation (probably a joke) like this:
rel_a -> rel_a

splitter handles this for the problem relations and it is not very time consuming.

Gerd

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