[Talk-gb-westmidlands] Birmingham City Centre & OS StreetView

[Andy Robinson (blackadder-lists)]

Brian Prangle wrote:
>Sent: 14 April 2010 8:13 AM
>To: Talk-gb-westmidlands at openstreetmap.org
>Subject: [Talk-gb-westmidlands] Birmingham City Centre & OS StreetView
>
>Things might look a little bit awry here over the next few days as I'm
>gradually re-aligning our edits (which were always only estimates given the
>crap GPS signals we got here) with OS StreetView. Although mostly it's just
>nudging the ways slightly, the time is taken up with realigning all the
>buildings, POIs and bus stops. Thos eof you regularly in the City Centre
>might like to check POI alignment. I'm concentrating inside the inner inner
>ring road and I started at the Northern end by the Children's Hospital and
>I'm just approaching the Council House. Outside the inner inner ring road
>the alignment doesn't look too bad but the building will be out.
>
>Generally the buildings do not have the fine level  of granularity that
>aerial imagery will give us.
>
>Regards
>
>Brian
>
>
Just a small word of warning, I've looked over several areas of data in the
west mids to compare the positioning of the OS StreetView rasters with our
own data. Generally the Streetview tiles tend to be shifted about 5m to the
south of our data. A one pixel possible shift was noted during the tiling
process but one pixel only accounts for a possible 1m error, the rest is
unexplained but may be differences in the complexity of the OS reference
frame when converting to WGS84. So although the OS work to 30mm horizontal
accuracy, that accuracy is of course in relation to their reference frame,
not ours, and so it's not surprising we wouldn't get an exact fit.

Cheers

Andy