[mkgmap-dev] [PATCH v1] Merge similar lines and ways

Sat Aug 15 12:31:06 BST 2009

Am 15.08.2009 um 13:04 schrieb Mark Burton:

> Will this cause a problem with ways that have been split on purpose
> because they are longer than the maximum allowed arc length?

No, not at all. The reason is that the merging of the ways is done  
before they are split again if necessary. The net effect is still a  
size reduction of the map (with the style I'm using). I hope that I  
also got everything else right: relations, turn-restrictions, etc.  
Please test and complain ;). Note that the argument "--merge-lines" is  
needed for the merging to take place.

The more detailed the OSM data becomes, the more the merging will be  
helpful. The main reason are the route relations. Here in my hometown  
all the bus routes are mapped and of course they go all over the  
place. Each time a bus route enters or leaves a street, the street has  
to be chopped up. Add to that a lot of cycle routes, hiking routes  
etc. and you see that the street gets chopped up into tiny bits.  
Depending on the map you try to create, you will ignore most of those  
relations and they will make no difference, so all those tiny bits  
have the same attributes. Merging them again will reduce the number of  
ways. This at least reduces the size of the map slightly and probably  
also helps routing and improves the drawing speed somewhat.

Regards
Thilo