The reason for this is because relative offsets are much harder to deal with than absolute offsets. When the relative positions are correct, you can still calculate how far things are from each other, how big they are, ... You don't need the absolute position for it. Even on the field, when using a GPS, the quality of the GPS position is often so low that you won't notice an absolute offset.
To minimise the number of relative differences, it's advised to base your data on a source that's more or less good in quality, and has a big coverage. As such, the Bing imagery was chosen as a base (without an offset applied, as any new mapper would get it in his freshly opened editor). When there are better sources available in the future (f.e. interpolated, high-precision positions), then everything in that region can be shifted by the then-known Bing offset. Regards, Sander 2014-11-06 11:55 GMT+01:00 althio forum <[email protected]>: > Hi HOT > > I am on task #591 - South Sudan Crisis, Cholera outbreak in Juba, mapping > with WorldView-2 imagery. > > Instructions includes: > Check in the vector data is correctly aligned on Bing imagery. Bing > imagery is the reference for the georeferencing. > > My question is about the first step i.e. What is the recommended offset > for Bing imagery: > (a) get from database > (b) set to offset: 0.00; 0.00 > (c) other > > Cheers, > > althio > > _______________________________________________ > HOT mailing list > [email protected] > https://lists.openstreetmap.org/listinfo/hot > >
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