Hi, Yes the adjustments for the latest WV2 imagery, put in the offset db, were based on the Bing imagery, supposedly (almost no GPS traces over Juba, unfortunately). BUT Bing updated its imagery over Juba; it is now dated June 23, 2013 and the georeferencing is slightly different, making the previous offset_db points obsolete. Tried to deprecate or delete them, did not get it, if someone knows the tip, I would be interested.
Considering the two imagery are now quite close, I would suggest to: - draw first on Bing and consider its georeferecing is good - then display the WV2 imagery, correcting the offset manually (was more complicated with the previous Bing imagery that was quite dark and quite old, what made the offset correction not easy considering the city is growing/evolving fast), and add the missing parts (from the test I made, new buildings here and there and more new buildings in the city limits, as expected). It this makes sense for everyone, I edit the job's instructions accordingly. Sincerely, Severin On Thu, Nov 6, 2014 at 9:51 AM, Sander Deryckere <sander...@gmail.com> wrote: > 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 <althio.fo...@gmail.com>: > >> 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 >> HOT@openstreetmap.org >> https://lists.openstreetmap.org/listinfo/hot >> >> > > _______________________________________________ > HOT mailing list > HOT@openstreetmap.org > https://lists.openstreetmap.org/listinfo/hot > >
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