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Am having an issue with the QGIS Georeferencer - I start with a fresh canvas but for some reason, the points always end up shifting a great amount (see screenshot).

I've double checked my points, and they are all correct - but you can see in the background, the referenced map image is upside down, and mirrored. Is there something I'm doing wrong? I'm converting a project from ArcMap and never experienced an issue like this there so I'm not sure as to where to go to with this problem.

Screenshot

It seems my error starts with 4 or more points, 3 or less and technically the points work but QGIS georeferencer gives out an error stating that it is "not solvable". BUT the points are exactly where they need to be (see below) enter image description here

Whereas, when I click to include the fourth point, which is in no means drastically different or wrong (as I've tried three different locations just to test the 4+ error theory), the georeferencer calculates that the points need to shift thousands of points away (see below) enter image description here

Below is my transformation settings window. One thing to note, after picking the same exact points, with the same exact transformation settings... it all of a sudden works. Not sure why, or how, but I'll take what I can get. Maybe it is something in my settings? (But again, I didn't change anything).

enter image description here

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2 Answers 2

Reset to default
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Something is way off with your dY values.

If I understand correctly, your image is just a scan from a paper map, but it is for some reason defined with EPSG: 3857. I would suggest resetting the georeferencer, define the image CRS to be the same as you project (4326 in this case) and the proceed to georeference it again.

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    You can change the CRS inside the georeferencer window under Settings -> Transformation settings, Target SRS. It should always be the same as the project CRS, if you pick your points from the canvas. The residuals should be small, otherwise the result is useless.
    – AndreJ
    Apr 26, 2016 at 6:24
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    I've done what you both have suggested, but it appears to be something else, as you'll see in my edited question... unless something like this is normal for this situation that is.
    – Matthew
    Apr 26, 2016 at 21:11
  • Have you tried opening a new .qgs file and georeferencing it anew? I have to admit that I don't know exactly why this happens. Also. what method are you using to georeference? 1st order? 2nd order?
    – HDunn
    Apr 26, 2016 at 21:17
  • I just tried to go through a new file and it does the exact same thing. I also made sure to reset the image file by just starting from the beginning with a new file - still nothing. And I know, quite the pain. To be honest though, I'm not sure what you mean by the method, just give me a hint and I should be able to answer it, still getting used to QGIS. Out of curiosity, would it be at all helpful to somehow share the files?
    – Matthew
    Apr 27, 2016 at 3:44
  • It surely helps if you can share the files. And a picture of your transformation settings window might be helpful too.
    – AndreJ
    Apr 27, 2016 at 11:58
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I had the same issue. Choose a different transformation type (e.g., Helmert instead of Linear) and resampling methods (e.g., cubic instead of Nearest Neighbor) - experiment a bit with different combinations. That solved the problem for me. Check out this link for explanations what the different options do: http://glaikit.org/2011/03/27/image-georeferencing-with-qgis/

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