[OSM-newbies] OS_OpenData

[Andrew Errington]

On Fri, 15 Jun 2012 04:56:16 Dudley Ibbett wrote:
> Hi
>
> 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?

Have you tried realigning the Bing imagery?  Often it is not accurately 
georeferenced.  Find a cluster of GPS traces that indicate some very visible 
feature (a road with some bends, or a roundabout is great for this) then 
slide the Bing layer to match.  In Potlatch hold down the spacebar while 
dragging.  In JOSM right-click on the Bing layer in the layer panel.

Also, don't forget to account for parallax error.  If you draw the shape of 
the buildings from their roofs you have to drag the rectangle (or whatever) 
to the corner of the building on the ground.  Similarly, if you are looking 
at the outlines but they don't line up with the roofs, look closer, maybe 
they line up with the ground footprint.

Finally, Bing alignment changes with each new set of photos they release.  
Every time it's wrong in another direction.

Best wishes,

Andrew