2

I am trying to georeference an old scanned map. I divided the scan in several parts. The original map uses an uncommon coordinate system (Equidistant Conic Projection according to De L'isle with Parallel lines at 50° and 53°), which I tried to manually create by using the following proj4 code:

Proj4: +proj=eqdc +lat_0=30 +lon_0=10 +lat_1=50 +lat_2=53 +x_0=0 +y_0=0 +ellps=intl +units:m +no_defs

To georeference the map, I used the qgis georeference plugin. However, something seems to go wrong in processing the coordinates. I entered the coordinates in degrees and used the following transformation settings (sorry in German, problem still occurs when changing to other coordinate systems): Dialogue Transformation Settings .

Below in the picture you can see the coordinate format (does this seem correctly specified?).

When I now run the georeferencing, and load the result into qgis, it does not display the coordinates correctly. In particular (compare mouse position/coordinate change), it seems that the picture is shrinked (no change in coordinates when mousing over the picture). Coordinates are displayed in Decimal Degrees. The pictures display two different mouse positions on the map.

Mouse Position 1

Mouse Position 2

What am I doing wrong?

I am a beginner in this field.

Improve this question
2
  • I think if you enter the coordinates in degrees (WGS84?), when you first load the raster and it prompts you for a CRS you should specify that it's EPSG:4326 ... or if that doesn't work, it should then be specified in the Target CRS option (third drop down box, first image of yours). Does fixing either of these work? As it is it's doing exactly as you instructed it to, you put in degree coordinates without telling it what CRS they're in.
    – she_weeds
    Commented Mar 30, 2018 at 14:48
  • Target coordinates should be in the CRS you added as target CRS in the dialogue box of the first image. So try EPSG:4258 there.
    – AndreJ
    Commented Mar 31, 2018 at 7:29

0

Reset to default

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.