[Talk-GB] OS OpenData StreetView Tiles now available
lists at mail.atownsend.org.uk
Wed Apr 7 12:36:16 BST 2010
Richard Fairhurst wrote:
> If you're tracing from _any_ source without first aligning it with a
> trustworthy ground reference (typically an average of existing GPS
> tracks), You're Doing It Wrong.
It seems that the sort of offset that there is with the new OS data is
different from what there was with NPE.
Here, for example:
There's a B road that is slightly S (5m maybe?) of where it should be in
the OS layer, but correctish for the surrounding unclassified roads
(based on underlying GPS traces). With NPE one whole area will tend to
be a few metres to one side, whereas a km to the east or west it'll be
offset differently - so (with Streetview) even after aligning the
general area there might be still bits that need alignments correcting
once traced. Obviously this requires multiple different good GPS traces
- the area above should have those as it's relatively open and not a
"natural canyon" as some of the surrounding areas are.
There's quite a lot of NPE-traced data that isn't aligned properly. In
the absence of any GPS traces if someone aligns it to OS Streetview
it'll be an improvement, but obviously not as much of an improvement as
actually going there and "saying what you see".
> FWIW, the 'resolution limit' in most of all our mapping is people's
> unwillingness to draw anything more than rudimentary join-the-dots.
Agreed, but even a straight line between two places where there's a road
is better than nothing at all, and can be improved later.
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