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

[Pieren]

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