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I am working on an OpenStreeetMap (OSM) building layer (I download the imposm GeoJSON in city Dar Es Salaam, Tanzania from https://mapzen.com/data/metro-extracts and used the building layer) and the Google satellite layer in Dar Es Salaam, Tanzania using QGIS. However, it seems to me that the Google map is misaligned.

overlaid image

I tried an imagery from OpenAerialMap and it aligns well with the OSM building layer.

enter image description here

Changing the current coordinate referenced system (CRS) in the bottom right of QGIS to match the CRS in the building layer does not fix the issue.

What are the possible reasons and is there any way to fix it so that they are aligned?

  • How did you "change the referenced coordinate system"? Did you actually reproject the data? Please be specific. – MappaGnosis Aug 3 '15 at 17:16
  • Edit your question and add a link to OSM map so we can have a look at the OSM source data as well. – user30184 Aug 3 '15 at 17:24
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    You should always keep in kind that either Google Maps, Openstreetmap or any other source might not be georeferenced perfectly. They may not have good sources for georeferencing, or did it in a quick-and-dirty way, or the photo is not taken orthogonal. – AndreJ Aug 3 '15 at 18:24
  • If you have a look with Potlatch or iD at openstreetmap.org/edit?editor=potlatch2#map=19/-6.79813/… and look at the Bing image background you can also see a few meters misalignment. It means that buildings have been digitized by using some other imagery as reference (or imported). This is an absolutely normal situation and there is nothing wrong in QGIS. Nor in Google/Bing images, there is no such thing as a perfect accuracy and the accuracy I see is normal for such satellite images. – user30184 Aug 3 '15 at 18:30
  • @user30184 Okay, i just want to make sure I did not do something wrong or miss anything. It is interesting to see it aligns with the drone imagery but not the satellite. I wonder how the OSM building layer is generated. – tsicwc Aug 3 '15 at 18:40
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I tried an imagery from OpenAerialMap and it aligns with the OSM building layer well.

Of course, buildings in OSM, most probably, were traced over this OpenAerialMap images, so they match them.

All satelite images could have alignment errors (as well as data traced among them). The quality of image referencing connected with:

  • Relief and Digital Elevation Model precision and quality.
  • Incline which under image was taken.
  • Visual references, with known coordinates availability.

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