[OSM-newbies] aerial imagery vs OSM data - which is correct?

[John F. Eldredge]

Pieren <pieren3 at gmail.com> wrote:

> On Tue, Feb 21, 2012 at 4:25 PM, Johann H. Addicks <addicks at gmx.net>
> wrote:
> >> Is it possible to *know* which of the two is right?
> 
> Probably none of them.
> The aerial imagery alignment accuracy depends on the concerned area
> (Bing is using many providers), the topology (mountains are more
> difficult to rectify than flat land) and may change on the zoom level.
> A single GPS trace is also not a good reference (can be +- 5 to 10
> meters, even more in urban zones). Best is an average of several
> traces done at different time intervals (with different satellites
> positions).
> Even better are survey/benchmarks maintained by governmental or
> private geographical agencies (if you are allowed to use them).
> 
> Pieren
> 
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One oddity I have noticed with both car and cell-phone GPS is that it seems to be more accurate when I am moving than when I am standing still.  
-- 
John F. Eldredge --  john at jfeldredge.com
"Reserve your right to think, for even to think wrongly is better than not to think at all." -- Hypatia of Alexandria