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R: [mkgmap-dev] Maps not for Cars and sharp-turns, U-Turns

From Marco Certelli marco_certelli at yahoo.it on Fri May 29 00:03:19 BST 2009

Made some test.

during fastest route serching, garmin gives a time penalty to turns. time penalty seems propotional to road speed so I think it just calculates a speed reduction due to turn and then a linear increase of speed up to the road speed.

for a steep 15° turn I got 357 second penalty on a motorway (road_speed=6 i.e 108km/h) and 237 second penalty on a primary (road_speed=4 i.e. 72km/h)

as the angle widens, the penalty is reduced (at 45° is about 1/3 the above values, at 90° about 1/8)

Ciao, Marco.

--- Gio 28/5/09, Felix Hartmann <extremecarver at googlemail.com> ha scritto:

> Da: Felix Hartmann <extremecarver at googlemail.com>
> Oggetto: [mkgmap-dev] Maps not for Cars and sharp-turns, U-Turns
> A: "Development list for mkgmap" <mkgmap-dev at lists.mkgmap.org.uk>
> Data: Giovedì 28 maggio 2009, 23:17
> After playing around a bit with maps
> and getting really confused why on some ways I could not
> route along with car/motorcycle setting, even though all
> access restrictions were sorted out, I found out that in
> case of very low angle of roads meeting, in car/motorcycle
> setting huge detours maybe made just to turn around.
> This is quite impractical as the best routing performance
> can be achieved with the car/motorcycle setting when writing
> the maps in such a way that bicycle use is assumed to be
> used as car/motorcycle. Using a bicycle there is no need to
> prohibit any kind of u-turn, but I think we can't get this
> out of the garmin programming but by changing the data
> source. Has anyone any idea how we could sort out this
> problem with preprocessing?
> Actually this might be usefull for car/motorcycle uses as
> well. It would be better to rely on turn-restrictions than
> on the garmin GPS simply deciding that at some place turning
> is impossible and making a detour to turn! I don't know the
> angle but I think if the meeting angle is lower than
> somewhere around 20° this happens. So roads meeting would
> need to be changed to meet at bigger angles than 20°. To
> really find out the angle upon which Garmin GPS/Mapsource
> decide a car can't turn (note avoid U-turn is not activated
> of course) would need some test maps however.
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