[mkgmap-dev] merge-lines and routing

Tue Apr 30 15:03:14 BST 2013

On 30.04.2013 00:04, GerdP wrote:
> Felix Hartmann-2 wrote
>> I am pretty sure, that routing is only done at the lowest resolution.
>> This doesn't have to be 24 - (but using mkgmap it actually has to be 24
>> - Garmin City Navigator uses resolution 23).
> yes, I think mkgmap is fixed on 24, but many places in the source code
> don't check for res==24, but level==0, that makes it difficult to
> understand.
>
>
> Felix Hartmann-2 wrote
>> Maybe confusion is caused by routable basemaps?
> yes, maybe the informations that I found while working on the
> overview map confused me. I like to find out if and how this
> can be used for routing, that's why I got stuck in the
> overview2 branch.
>
> Gerd
I just checked the overview map of City Navigator. You're right it is 
routable (only at level 0 of course). So maybe Basecamp/Mapsource use it 
for long distance routing. However there is basically not much in them 
that is routable.

Highways are universally road_class=4, road_speed=6,
important primary rods are road_class=2, road_speed=4
and less important primary roads --> especially those that are 
"dead-end" on the overview map, are road_class=1, road_speed=3.
Some trunk roads --> (Schnellstraßen) especially in Germany are 
road_class=3, road_speed=5.

The speeds / classes on the primary roads, don't necessarily correspond 
with the speed/class in the actual map.
I don't really know though, if OSM material is of any use for creating 
such a routable basemap/overview map. The oveview map of City Navigator 
is very generalized. Highways are not entered for each direction as 
oneway, but as twoway streeets.

So we would need to get some non OSM generalized map data - in order to 
create a working routable basemap.

I would say that getting several map layers into the overview map, 
should be implemented first. Of course also for Overviewmaps, ONLY the 
level=0 is routable, just like for normal map images. Additional levels 
aren't routable. Then at some point we might need to move to static 
basemap content, based on either super simplified OSM, or based of some 
other databases...
>
>
>
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