[Talk-GB] Separation of sources

Ed Avis eda at waniasset.com
Sat Apr 10 11:01:51 BST 2010

Simon Ward <simon at ...> writes:

>I’d just like to see something where ground surveyed data is the
>ultimate, and it’s not clear to me that it is the ultimate now.

I've done a fair bit of ground surveying, but all of it has been from the
starting point of an existing map - usually one traced from the aerial imagery.
If the street layout appears slightly wrong I won't usually correct it, because
the GPS precision is not good enough in heavily built-up areas.  (Only if there
is an obvious tracing mistake or a missing street will I use the GPS data to
make changes to geometry.)  So what we have at the moment, in the UK at least,
is already a mishmash of photographs, ground survey, and (in rural areas) tracing
from older OS maps.  A pure survey-only OSM has not existed except in the very
early days before Yahoo photos.

If what you mean is that in the event of a disagreement, the only way to check
map data is to look on the ground, then of course this has always been true.
I don't think importing from any other source changes that.

Do remember that the OS maps have also been produced largely by ground survey,
and their surveyors are no less skilled or dedicated than our OSM volunteers.

Ed Avis <eda at waniasset.com>

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