For those of you that have been doing cleanup after the redaction, are you
noticing anything in particular that could benefit from automated help?
For example, in an area I looked at yesterday, I saw a bunch of "sawtooth"
formations, where a way would depart drastically from the true path of the
road, then come back to a node on the road, then a node away again, etc.
These nodes that were off the road were presumably those that had been
moved to the correct alignment by a non-agreeing user, and were therefore
moved back to their wrong locations by the bot.
Example:
http://www.openstreetmap.org/?lat=33.744884&lon=-117.608049&zoom=18&layers=M
I think these could be identified programmatically in a similar way as a
smoothing algorithm: Calc the bearing b12 from p1 to p2, b23 from p2 to p3,
and b24 from p2 to p4. If b12 is closer to b24 than b23 by a specified
amount, the line is smoother without p3 in it, and is possibly corrupt. A
little mathematical creativity can avoid having to calc the actual bearings
with arctan on every point, since it's really the relative ratios that
matter and not the actual values of the angles themselves.
Another thing is that these sawtooth ways tend to cross other ways without
intersection, so this is a good indicator, too.
Lastly, I'm noticing orphan nodes in areas that need work.
These would make good layer(s) in the Geofabrik OSM Inspector.
Other ideas?
--
Alan Mintz <[email protected]>
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