I am trying to georeference a building using 4 coordinates, which produces the following result: enter image description here

After georeferencing, shouldn't the image be distorted to match the red lines? The loaded result is as follows: enter image description here

I am not sure what I might be missing. Both layer and project's CRS are set to WGS 84.

Here is the report tableenter image description here:

Any ideas?

Answer: Just changed the transformation type to Polynomial 1, which produced the following result: enter image description here

  • 2
    Which transformation type did you choose? Were the residual acceptable? WGS 84 is very strange for a floor plan.
    – Zoltan
    Commented Nov 4, 2016 at 20:44
  • The transformation type was set to Linear. I have chosen WGS 84 since it's what google uses. Not sure about the residual values... going to upload a picture in my question above.
    – Apidcloud
    Commented Nov 4, 2016 at 21:35
  • TPS is the only one to convert each ground control point en.m.wikipedia.org/wiki/Thin_plate_spline and distort as you described.
    – user30184
    Commented Nov 4, 2016 at 21:46
  • Helmert and Polynomial 1 worked too, though
    – Apidcloud
    Commented Nov 4, 2016 at 21:51
  • Linear transformation type doesn't allow rotation use Polynomial 1 (affine) transformation.
    – Zoltan
    Commented Nov 5, 2016 at 18:11

2 Answers 2


Please read the documentation of the different transformation types:

The Linear algorithm is used to create a world file and is different from the other algorithms, as it does not actually transform the raster. This algorithm likely won’t be sufficient if you are dealing with scanned material.

... Therefore, no surprise that the image was not rotated.

  • oh well... My bad about that. I tried with Helmert and it rotated. Thanks for the help!
    – Apidcloud
    Commented Nov 4, 2016 at 21:47

Not really. If you watch closely, the coordinates you input just make the building spin a little bit anti-clockwise; the proportion is maintained. Place both your index fingers and thumbs at the red dot indicating the coordinate, then simultaneously follow the red line with your fingers. You'll see that the blueprint just slightly spins. Since you don't have a referential (the environment behind the image is blank) it looks the same.

  • So you mean that since the proportion is more or less maintained, it shouldn't spin the image as well? That's what is confusing me.
    – Apidcloud
    Commented Nov 4, 2016 at 21:36

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