[OSM-talk] When images are not calibrated

[Michael Collinson]

As there is no standard image reference, I personally don't adjust 
positions at all until at least one nearby road has GPS traces that I 
can view. Most of what we do with the data involves relative rather than 
absolute positions. For example, it is useful to know that the post box 
is on the south-east side of a cross-roads. It is not very important to 
know the exact location. I therefore believe that adjustment can be left 
until the map is quite mature. The one disadvantage of that is that you 
may have a lot of things to move!

At least 4 traces are good. If less, then some of them may be simply bad 
traces or you may be seeing a pedestrian or cyclist on just one side of 
the road. A road with a curve or junction in it is best so that 
adjustment can 2-dimensional. I then adjust the road first, and then 
move the imagery to align with the road.

Caveats: Image offset can be very local, so check often. Traces can 
sometimes "smooth out" a road, look at the image too. Can be problematic 
due to parallax in very hilly areas, not a problem in Arboga I think.

Happy mapping,
Mike
Vallentuna kommun

On 2021-08-17 13:56, Markku Siipola via talk wrote:
> I'm a newbie recently started to update OSM in my neighbourhood 
> (Arboga, Sweden) with JOSM.
>
> I have learned it's important to calibrate the Bing images. For 
> example on roundabouts. I quickly noticed that most of the buildings 
> in Arboga was somewhat misplaced (about 5-10 meters). Different errors 
> by different authors. So I adjusted the positions of all the buildings.
>
> But when I open the same location in ID or Potlatch, all buildings are 
> again little misplaced. Probably because the images in these editors 
> are not calibrated. But how many of users of these editors know the 
> images should be calibrate? Probably not many. And is it even possible 
> to calibrate the images in these?
>
> So now I'm waiting for someone adjust all the buildings in Arboga 
> again, because they are "misplaced"!
>
>
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