[mkgmap-dev] Questions regarding routing

Fri Jun 7 22:30:07 BST 2013

The idea behind it was that one could priotize or depriotize roads close 
to Point X.

However it is seriously flawed in so far, that mkgmap:road-min-speed / 
max-speed doesn't work.
If you tag road-min-speed=1, the road previously was road-speed=0 and 
the command is road-speed=-1, it will actually increase the speed to the 
min-speed.
However the intention is only that road-speed>0 are not decreased to 0 
if that command is given. It should never increase...

Else the problem is, that the distance it works, is very short anyhow, 
now that roads are split up into very short distances everywhere.

To improve routing, a much better approach would be to check the 
finished routing graph for heavy road-class changes on intersections. 
Garmin doesn't like to route from a road-class=4 onto a 0-1. Only 2 or 3 
are liked. The max difference should be 2. However that will be 
difficult to achieve.
Also high angles on intersections could have an automatic road-speed 
decrease by 1 or 2 (depending on the current state) - or even more 
smoothing out - that is still something going crazy. A turn of 160° is 
like minimum 1 minute time penalty...
On 07.06.2013 22:59, GerdP wrote:
> 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.
>
> Gerd
> Gerd
>
>
>
> --
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-- 
keep on biking and discovering new trails

Felix
openmtbmap.org & www.velomap.org