Dudley Ibbett wrote:
I wonder if anyone that has had experience of using
OS_OpenData_Streetview in the UK could comment on its accuracy. I
have been doing some mapping through Earl Sterndale in Derbyshire and
note that most of the buildings are drawn with the source tag:
OS_OpenData_Streetview. Many of the buildings positions and shape are
way off compared to Bing. Should I consider adjusting them according
to Bing or leave them alone?
Generally speaking, in an area that's flat and not hilly, I'd expect
OS_OpenData_Streetview to be within 2-3m of an average of lots of GPS
traces. There's the occasional anomaly, where roads come out the wrong
shape or features are misinterpreted (presumably as a result of tracing
from aerial photos), but it's usually there or thereabouts.
My gut feeling for the Bing imagery in similar conditions is that
usually it'll be more accurate than OSSV - to the point where you can't
tell an offset from the centre line of lots of GPS traces. In some
cases there are odd unexplainable offsets though.
The problem with Earl Sterndale though, is that it's at a place where a
number of valleys meet - hills on all sides. It's exactly the sort of
place where there might be problems with any and all of OSSV and Bing
imagery. I've also seen (e.g. in Matlock) consistent GPS trace offsets
on the side of a hill, so care even needs to be taken with those too.
In Earl Sterndale though I'd probably trust the average of the GPS
traces, as they're consistent along the roads and there's no obvious
anomalies corresponding to hills or gaps in hills.
Looking here in Potlatch:
http://www.openstreetmap.org/edit?editor=potlatch2&lat=53.198777&lon=-1.863473&zoom=18
and looking the OSSV-drawn buildings against the Bing imagery and the
underlying GPS traces, it does look like roads and buildings are offset
maybe 5m to the south relative to traces. Bing's maybe 2m to the south
relative to GPS traces I guess?
Whether you'd worry about this or not is a different issue - knowing
that the Quiet Woman pub is 1st on the left after the T-junction is
useful; knowing whether that's 40m or 45m away isn't particularly more so.
Cheers,
Andy
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