[mkgmap-dev] Putting the DP code under the microscope

Sat Jul 25 13:15:36 BST 2009

Hi Felix,

Am 25.07.2009 um 13:05 schrieb Felix Hartmann:

> Yeah, merging roads if possible would be great. Even more important
> would however be smoothing of curves. i.e. make serpentine corners on
> mountain streets more smooth, because otherwise if there is a say 160°
> corner, it will add a big time penalty, which in a car is more or less
> correct, but on a bicycle overrated.

This is actually not that difficult, because you can do it with an  
additional filter for the ways. It is a local modification for each way.

> However, how do you want to do the merging without loosing attributes
> (i.e. roadname changes, bridge, etc..), I think this could only work
> by running after the main processing, and merging everything identical
> if possible.
>
> Otherwise before merging there needs to be a check whether there is
> not a rule in the style-file that would change either the name of the
> road OR the type (0x??) of a road. If both not changed then merge it.

The trick would be to do the merging on the data just before it is  
converted into the Garmin format, after the style files are applied.  
Then you have the final settings of all attributes and the name and  
can merge only those ways that are identical in that respect. This is  
also the point when the filters get applied to the ways. The problem  
here is that the filters see only each way in turn, so they can only  
perform modifications on a single way. Unfortunately it is not that  
easy to find a place in the source code where you could apply the  
merging of ways, which is the reason why I haven't had a go at it yet.

Regards
Thilo