[OSM-talk] tracklog credibility
stefan.baebler at gmail.com
Sat Jul 14 07:51:02 BST 2007
user jcomeau_ictx wrote:
Can anybody comment on the legality of using Google Maps to get
approximate lat/lon points, formatting those points into a GPX file, and
uploading to OSM? I just want to know if I can be open about it, or if I
have to be sneaky. It's inaccurate enough that nobody could tell, by
looking at the data, how it was sourced... but if this is really a Bad
Idea, I'll just have to come up with another method, or save up for a
As far as i understand the legalities this shouldn't be done.
This brings up an issue how a GPS tracklog could be trusted.
Basic GPX is simple to produce, requiring no more than coordinates,
which can be artificially "enriched" with timestamps to be technically
acceptable for OSM.
OSM track importer could check and warn about traces where
-points have same time
-points have non-continuous time
-speed is constant or varies too much
In theory, we'd need some signature from the source (satellites in this
case). Gps units could also add digital timestamps and digitally sign
the coordinate pair :) But then we'd need to trust satellite owners and
GPS unit manufacturers.
However, checking satellite signal strength, combining that with
coordinates and checking those against known satellite orbits (those are
used for AGPS) could be viable. Unfortunately same orbit data could be
used to make fake traces if someone would want that very badly.
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