Hi, I just updated the job <http://tasks.hotosm.org/project/591> instructions as proposed below. SUmmary: first Bing 2013, then WV2 to complete.
Sincerely, Severin On Tue, Nov 11, 2014 at 3:48 PM, Severin Menard <severin.men...@gmail.com> wrote: > 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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