[OSM-talk] When images are not calibrated

john whelan jwhelan0112 at gmail.com
Tue Aug 17 12:51:51 UTC 2021


I suspect it is difficult to do.  A GPS point is usually plus or minus 5 to
10 meters, trees and tall buildings can affect the measurements.   I made a
GPS track down a street with buildings once in Ottawa, the GPS track was
curved in a zig zag but standing at one end of the street I could see it
ran in a straight line.  That was using a Garmin GPS which is usually
considered fairly accurate.

Big satellites, the most accurate ones, have a raw accuracy of around 60
meters before the images are corrected.  I think most mappers use Bing but
that is only by convention.

There are more accurate GPS location tools but they are more expensive than
the average mapper can afford.

I suspect 5 to 10 meters is about as good as we can reasonably expect.

Cheerio John

On Tue, Aug 17, 2021, 08:04 Markku Siipola via talk <talk at openstreetmap.org>
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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