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I have to georeference a few hundred JPEG maps in QGIS. Each of these maps has an average size of 20 MB. After georeferencing, these maps must be loaded into ArcGIS on another computer, of course correctly georeferenced. I just have access to QGIS, while my colleague, who has to work with these maps later, has only access to ArcGIS.

Up to now, I tried several attempts in QGIS. Georeferencing itself isn't problematic, but the outcoming filesizes are too big for each single map (mostly greater than 100 MB, sometimes up to 300 MB). While georeferencing I tried the compression options "deflate", "lzw" and "packbits", but all resulting files are still too big for handling them on my colleque's machine.The output files are all in GeoTIFF format.

I tried to georeference the maps without producing a GeoTIFF but only a wld file. After doing so, the map could not be loaded into ArcGIS without showing the warning "file has no spatial reference" even if the original JPEG map and the world-file are stored in the same location on my colleague's PC.

A quick search on this site did not lead to satisfactory results.

Is there a way in which I can georeference JPEG files (20 Mb) in QGIS in a way, that the resulting file shows similar sizes as the original file and can be correctly displayed in ArcGIS on another computer afterwards?

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    JPEG is a lossy format, while TIFF is not. Georeferencing usually increases the image dimensions (and therefore storage requirements) due to rotation. So your task can only result in larger files. ArcGIS will accept standard .jpw world files, but you'd have to dial down image quality to keep the storage size the same.
    – Vince
    Commented Oct 1, 2019 at 23:51
  • I tried that. I had to use GIMP to cut off the edges of the map and saved it as .tif-file. Afterwards I used QGIS georeferencing tool referencing it. How can I choose between GeoTiff and .jpw world file? When finishing the georeferencing, no .jpw-file is created. I only got a .tif-file and a .wld-file if I chosse the option "only create world file" in the options for the transformation. But this file can not be correctly loaded into ArcGIS. We also tried georeferencing using ArcGIS itself and here it works perfectly.
    – MAT
    Commented Oct 2, 2019 at 0:21
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    You can use JPEG compression in the GeoTIFF or you can output a .wld file (the file has no spatial reference" warning just means you need to tell ArcGIS what the CRS is, or ignore it if the ArcGIS map CRS is the same as the JPEG georeferencing CRS or you can create a .prj file with the CRS text in it).
    – user2856
    Commented Oct 2, 2019 at 0:48
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    The difference in size comes from different compression methods. QGIS does not give on option to select JPEG compression with the GUI, but can let Georeferencer to create you a GDAL script. Option is in the File menu. Find the gdalwarp command. Edit the compression method option to contain -co COMPRESS=JPEG and run the command manually from the command window.
    – user30184
    Commented Oct 2, 2019 at 13:40
  • @Vince, TIFF does not prevent compressing the image data with some lossy method. GDAL GeoTIFF driver supports JPEG and LERC compressions which are lossy gdal.org/drivers/raster/gtiff.html.
    – user30184
    Commented Oct 2, 2019 at 13:46

1 Answer 1

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You can try the following

  • Convert the GeoTiff file to another format. Use the Translate (Convert Format) processing algorithm and save the output as a file of type JPEG2000. Make sure the extension of the file is set as .jp2. It should result in a lower file size.

  • If you can live with 8-bit data types, you can apply JPEG compression on the GeoTiff using the same Translate algorithm. Select the profile JPEG Compression enter image description here

  • Another way to reduce the size is to set the target resolution in Georeferencer. Lowering the resolution will result in smaller file size.

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