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When importing a JPG map using QGIS's georeferencer plugin, the resulting map layer is distorted and does not look anything like the map that I am trying to import. I can't work out what is causing this map distortion.

Screenshots of the steps

Step 1 Step 2 Step 3

2 Answers 2

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If you're using just two points for georeferencing try using "Helmert". Definitely not thin plate spline. The map looks to be for somewhere in England, so set the target CRS to EPSG:27700.

Nick.

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  • do you know an article somewhere explaining the differences between the methods ?
    – nickves
    Jun 16, 2013 at 20:54
  • Thanks, Helmert was the transformation type that worked. Using linear just plotted the points on the map. Jun 17, 2013 at 10:16
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    Sorry, I should have been more specific. Use "Helmert" as the transformation type and "Linear" as the resampling method.
    – nhopton
    Jun 17, 2013 at 13:40
  • @nickves This isn't covered in the manual in any depth, but there are some useful videos on YouTube, for example. For me, the two-point method outlined above works well provided that the map image is not distorted and that two accurate GCPs are available. N.
    – nhopton
    Jun 17, 2013 at 13:59
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The distortion is caused by your selection of target SRS, and the CRS you are using in your QGIS project.

As soon as you are using a different CRS in QGIS as the one used to create your the raster (jpg file), you will see this distortion.

This normal behaviour.

If you're setting the same CRS to the QGIS project, the image shown will resemble your original data (providing you have performed a correct georeferencing).

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