On Wed, 3 Dec 2008, John Rowland wrote:

Tom Anderson wrote:
"Tom Anderson" wrote in message
h.li...

While pondering the nature of southwest London, i turned to
OpenStreetMap:
http://openstreetmap.org/

The fact that it's a straight line makes me suspect it's based on a
simple error or glitch: someone meant to enter a road linking (eg)
points 100 and 734327, but typed 734372 for the end, which happens to
be rather far way. Possibly the sort of thing some simple validation
steps would catch.

If data was hand-entered in this way there would be such errors all over
the shop.

Unless the data is mostly entered automatically, but there are occasional
hand-edits.

I imagine it's actually caused by a GPS error, where a GPS unit suddenly
thought it was in Portugal for a few seconds, and the user didn't check
before submitting the data.

Also possible.

tom

--
A complex system that works is invariably found to have evolved from a
simple system that worked. -- Gall's Law