Hi Felix,
Am 03.06.2009 um 12:06 schrieb Felix Hartmann:
Is it possible to encode arbitrary maxspeed values or can we only
set in steps of 10km/h?
For example having road road_speed=7 associated with 35km/h, road
road_speed=6 with 27, road_speed=5 with 23, road_speed=4 with 20,
road_speed=3 with 17, road_speed=2 with 10 and road_speed=1 with 5km/
h. The difference this should make would be enough to only set
road_class=2, 1 and 0 and avoid the big time penalties for sharp
turns that happen in road_class 4 and 3.
This would be great for bicycle maps.
That would be great indeed.
In Mapsource one can change the speed oneself, I noticed that
dividing default speeds by a factor of 3.5 produces pretty good
estimation of arrival times for bicylces (when using the car/
motorcycle setting, as bicycle produces rubbish routes) but on the
GPS this is not possible.
@Thilo, do you understand the code good enough to write a patch for
this if possible.? I have problems understanding in which files the
maxspeed is handled.
I have not really looked into the Garmin encoding part of the code,
but I could invest some time if it helps. From what I know there are
only those few road_speeds available in the format. *But* maybe there
is some part in the header where one can set what actual speed each
road_speed corresponds to (this is pure speculation).
Somebody mentioned also that the GPS units will "learn" the speed you
are actually driving and use that for their calculation. If this is
speculation or based on facts I don't know. At least with my Oregon
300 I doubt it: As I use it all the time with my maps I'm cycling
always in the car mode. So far the ETAs are still very wrong. If the
GPS would learn the speed they should become more realistic over time.
Perhaps we can build a Wiki page somewhere where we can collect all
"hard evidence" about the routing? How about setting up an artificial
map that we can use to test the routing, ETAs and so on? Especially
keeping in mind that there might be a difference between different GPS
units, firmware revision and so on. If there are routing parameters
that the GPS units "learn" about their users that would really f*ck up
our tests.
@Marco Certelli: You've already started some tests. If you could write
down what you did on some Wiki page so that others can repeat your
tests that would be really helpful.
Regards
Thilo
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