[mkgmap-dev] Questions regarding routing

Fri Jun 7 22:25:45 BST 2013

El 07/06/13 22:59, GerdP escribió:
> Hi Carlos,
>
>
> Carlos Dávila-2 wrote
>> El 07/06/13 21:45, GerdP escribió:
>>> Questions:
>>> 1) If a road with road_speed=4 has e.g. 10 points (= OSM nodes) , and the
>>> 3rd point has tag
>>> mkgmap:road-speed=-1 and the 8th point has tag mkgmap:road-speed=+1,
>>> what is the expected result?
>>> I would assume that the road is split into 3 parts, one containining
>>> points
>>> 1-3,
>>> one the points 3-8, and the last one the points 8-10.
>>> The 1st part would use the unchanged road_speed value 4, the 2nd part the
>>> the value 3 and the last part the value 5.
>>> (if this doesn't introduce any short arcs, else splitting makes no sense
>>> for
>>> these tags)
>>> Correct?
>> If I recall correctly, if a node is tagged with mkgmap:road-speed it
>> affects the portion of the way from the node before to the tagged one to
>> the node after it, so the above example will result in section 1-2:
>> road-speed=4, section 2-4 r-s=3, section 4-7 r-s=4, section 7-9 r-s=5
>> and section 9-10 r-s=4
> yes, I think that is what happens. I just don't understand why it is coded
> like that.
> The default style doesn't use this feature, so I don't know how it is used.
> My thought was that a OSM node has some kind of speed limit tag and that is
> translated
> into a mkgmap:road-speed tag. If that is correct, I would assume that the
> speed limit
> is true as long as no new node with another one is found. Of course this
> assumes that
> all different speed limit signs are points with the corresponding tags.
mkgmap:road-speed is not used for speed tags in the OSM data but for 
elements (nodes) that may affect the surrounding section of a way. For 
example, if a residential way has a node tagged traffic_calming=* you 
may drive at say 50 km/h most of the way, but you'll have to slow down 
at that point. It can be implemented in the points style file as:
traffic_calming=table { add mkgmap:road-speed = '-2'; add 
mkgmap:road-speed-min = '1' }
traffic_calming=* { add mkgmap:road-speed = '-1'; add 
mkgmap:road-speed-min = '1' }