[mkgmap-dev] Simplifying ways

Sat Nov 28 23:28:44 GMT 2009

>>>
>>> I noticed that some Garmin maps display 1:1 to openstreetmap data, 
>>> but on route calculation show up to 10% shorter distance. Maybe here 
>>> only routing nodes are simplifed (straighter line).
>>
>> Sorry, could you explain in more detail? I'm not sure what you mean 
>> here.
>> 'Simplifiing routing nodes' is the thing, which tries Mark with his 
>> bogus node patch.
> Well I noticed this on a serpentine way in the Swiss Alps.
>
> I routed over Topo Swiss v2 and distance was 2.3km, then on 
> Openstreetmap mkgmap created map 2.8km. Though when putting the maps 
> transparent above each other, there was nearly no difference to tell 
> in the shape of the ways. From plain eye openstreetmap seemed to be 
> shorter even. Therefore I assumed that the way it was showing was 
> longer than the way the routing happened on. Also my bicycle computer 
> showed 3.1km on the supposedly 2.3km part of the route.
> .
>
Thats interesting.
The distance for routing is contained in the routing tables and these 
are not touched from me in any patch.
I really don't know, as I have never looked into it, but here is an 
assumption:
I think the arcs conains the distnace from node to node. Maybe here is 
the direct line from node to node calculated and not the real length 
from the winding serpentine.