I started with the Japan project https://tasks.hotosm.org/projects/9023 today and saw there is a big misalignment of the Maxar Premium and the Bing imagery. Maxar seems to be newer, because it contains some buildings that are not on Bing, but when you get an area with buildings mapped using Bing, and then switch to Maxar for mapping the rest of the buildings, the old mapped buildings do not fit to the imagery. Can anyone who know this application better than me please take a look and check if the imageries can be aligned for the whole project?

asked 10 Jul '20, 16:55

Tobias%20Barth's gravatar image

Tobias Barth
accept rate: 0%

In Japan, use GSI standard map as a guide.

(11 Jul '20, 12:54) Kovoschiz

There are attempts to save imagery offsets, but as each imagery layer is actually a composite of multiple captures with unknown post-processing and extents and sometimes offsets even differ between zoom levels, this is quite difficult to accomplish.

In iD editor the offset for a particular area can be adjusted by scrolling to the bottom of the pane showing the list of available images and attempting to drag the grey area surrounding the text describing the offset.

If the region is hilly then the distortions required to flatten the imagery can result in significant disagreement between the appearance from various providers. GPS traces are generally considered the most reliable positioning provided there are enough traces to allow for scatter and they aren't in the midst of highrise building which can reflect signals.

Imagery-wise I would normally expect a local agencies orthophotos to be more accurately positioned than any of the global providers. iD and JOSM list some Japan specific layers, but I have no knowledge of their accuracy myself.

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answered 10 Jul '20, 19:02

InsertUser's gravatar image

accept rate: 20%

Thanks for your fast answer. Seems to be a complex problem because of the 2d projection of a 3d world etc.. Follow-up question: Is there a way to move an entire building, other than moving point by point?

(10 Jul '20, 21:44) Tobias Barth

Yes, either right click and use the dot with four arrows radiating in the cardinal directions or the shortcut M. For most buildings the sQuare command is heavily used too. Although for the previous editor, this page still contains some useful tips for buildings. (PS this should technically be a new question)

(11 Jul '20, 00:01) InsertUser

@InsertUser GSI photos aren't necessarily aligned with GSI standard map, but the latter is a possible "standard" reference.

(11 Jul '20, 12:55) Kovoschiz
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question asked: 10 Jul '20, 16:55

question was seen: 435 times

last updated: 11 Jul '20, 12:55

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