[mkgmap-dev] Questions regarding routing

Sat Jun 8 06:37:50 BST 2013

Hi Carlos,

thanks for the explanation and the example, I think I understand the idea
now.

Gerd

Carlos Dávila-2 wrote
> 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' }
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