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Hello everyone! When I'm editing the map I tend to use ESRI imagery as it is much clearer than Bing and Mapbox. I traced a parking garage with ESRI imagery before, out of interest, switching to Bing to see what it would look like. I noticed that the imagery was completely offset to the right and that everything I had traced was in the wrong place. I then compared Mapbox and Bing and noticed that they both had the same positioning, but Esri didn't. I am going to record some GPS points later but I would like some opinions. Which imagery is correct? |
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Most aerial imagery we use in OSM is "consumer grade" and hence not super precise. Which of the available imagery layers fits reality best is very dependent on the area you're looking at; you'd have to tell us where you are editing for us to make a guess. Recording some GPS traces (or switching on the GPS trace view in your editor) is a good way of checking the aerial imagery alignment. Most editors will also offer a way to correct the position of the aerial image so that it matches the GPS traces, and to save that correction for future use. Sadly, attempts at creating a global database of imagery correction offsets like https://wiki.openstreetmap.org/wiki/True_Offset_Process or https://wiki.openstreetmap.org/wiki/Imagery_Offset_Database have yet to gain traction. 1
The offset is not only dependent on the area but might also change between zoom levels. Esri used to be super precise in my area but around half a year ago they changed the imagery on lower zoom levels which is off by several 10s of meters. Higher zoom levels retained the previous accurate images.
(12 Feb '20, 08:55)
TZorn
Hey Frederik, thanks. I'm editing north London and have found out that Esri is off by about 10 metres. I've adjusted the offset, but thanks for the answer
(12 Feb '20, 09:59)
inquisitive
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