[OSM-talk] Google Maps comparison

[Andy Robinson]

Dair Grant wrote:
>Sent: 10 October 2007 8:02 PM
>To: talk at openstreetmap.org
>Subject: [OSM-talk] Google Maps comparison
>
>Hi,
>
>I recently finished mapping the town I live in, and thought it
>would be interesting to do a detailed comparison with Google
>Maps (or really, the TeleAtlas data it is based on).
>
>Once the OSM version was finished, I reviewed each street to
>check it against the equivalent in GM. You can see the results at:
>
>     <http://www.refnum.com/osm/gmaps.html>
>
>Although the missing road figures are inflated by a "new" (2004)
>housing estate, the overall error rate is surprisingly high.
>
>
>This should also be confirmation (if anyone was in any doubt)
>that entering data into OSM by tracing a commercial source is a
>really really bad idea.
>
>Many of these errors will probably go uncorrected for years, and
>it would be extremely easy to insert deliberate errors without
>affecting the usability of the map.
>
>It would also be trivial to re-survey an area to detect these
>kind of errors, then use that list of corrections to check for
>identical mistakes in a suspect map.
>
>

That's really, really nice work. I was quite struck by the sheer number of
differences. I've seen plenty in my area but as yet haven't looked closely
enough to see just how many. Your results suggesting 9 per square kilometre
of urban area would make an astounding number for the whole country if it
ramps linearly.

As Cory has suggested, we need to make more of these findings..... I feel a
blog coming on.

Cheers

Andy