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Specific example: Motorway/trunck-road A-7 between Estepona and Marbella (and between Marbella and Fuengirola) has most of it's speed-limit at 80. There are, however, also parts (maybe 20 kms. of the 90 total) where 120 kms. is allowed. The road is not drawn as a complete line (f.e. part between Estepona and Marbella consists of maybe 20-30 different connected stretches in either direction). Is it enough to set the beginning point of the 80/120 km limit? Will the offline-routing-app (whichever) recognize there is no change in speed limit and advise the user to stay at the earlier specified speed until otherwise specified, or should it be set for every part of the road. |
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The general answer to this is: You have to ask the provider of your offline routing app. It is them who decide how to interpret OSM data. But usually, the maximum allowable speed is tagged onto the way to which it applies, and the assumption is then that you are allowed to go at this speed for the whole length of the way. So most mappers would apply the If someone works with an excerpt of the huge planet file the edge segments of the road may be missing since they are outside the border of the excerpt, so in my opinion the safe bet is to tag each and every segment as already suggested by Frederik.
(01 Aug '12, 18:19)
gnurk
Two ways to collect the speed limits would be (1) gpx trace while driving legally then with some mapping software clicking on the trace indicates your speed at that point. (2) Record it on a video using the limit signs and time to correlate to gpx position. both a lot of work.
(02 Aug '12, 11:02)
andy mackey
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@andy mackey: possibility would be to look in the archives of regional laws and governmental orders. In some countries, speed limits are ordered by the regional council in such a way: "on the A1 eastbound from km 25+321 until km 27+112 the maximum speed limit of 100 km/h will be valid from 1st of october, 2007". Sounds even more cumbersome...
(03 Aug '12, 10:22)
moszkva ter
I agree moszkva-ter best to go back to OSM basic idea of "crowd sourcing" so locals do their own "back yard"
(03 Aug '12, 16:56)
andy mackey
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