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I am trying to learn my colleagues to display measured data (ASCII) in maps relatively easily. I can prepare project, color and symbology style for the point layer and background map.

I also found good way to get background map (PNG + world file) for offline use via MOBAC and OSM. MOBAC uses EPSG:3395 WGS 84 / World Mercator and I have the appropriate PRJ file. However, I found out, that QGIS does not use the PRJ for rasters and load them always using default CRS (in my case EPSG:4326).

Is it possible to make QGIS load the CRS settings from the PRJ (or other file) without need to set the CRS manually for every raster?

thanks

  • Hi, after QGIS upgrade I found out, that it reads the projection from the *.aux.xml file which MOBAC generates along with the *.pgw world file and the PNG image. Works out of the box for me (QGIS 1.7.4) - example file: dl.dropbox.com/u/6066212/Test_Prague.zip (600 kb). Really useful. :-) – Juhele May 3 '12 at 9:44
  • I am facing the same problem. I can't find way how to save information about CRS with JPG/PNG files. Well except of converting it to Geotif which is very inconvenient. Just wondering if there is some bettter option now in newer versions of QGIS? – Miro Oct 8 '14 at 1:24
  • Mmm, so it is only at stage "nice to have" after last 2 years... hub.qgis.org/issues/4236 Well, once I will get better with writing plugins for QGIS I could try to make plugin for this :) – Miro Oct 8 '14 at 1:32
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Try:

(menu) Raster > Projections > Assign projection

This procedure writes CRS to file. Next time you load it QGIS will not ask you for a CRS.

  • Hi, but this requires converting all the maps to Geotiff - it increases the time I would have to spend with the map preparation... – Juhele May 3 '12 at 9:40
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Hopefully it will be implemented one day (http://hub.qgis.org/issues/4236).

Meanwhile it is possible to use gdal_translate from within QGIS which creates *.aux.xml holding information about CRS (projection). Opened in text editor it looks like this:

<PAMDataset>
  <SRS>PROJCS["WGS 84 / Pseudo-Mercator",...]</SRS>
  <GeoTransform> ... </GeoTransform>
  ...
</PAMDataset>

This can be done only once for desired CRS (projection) - if in text editor you remove: <GeoTransform> ... </GeoTransform> which specifies location which must be loaded from specific world files for every image.

So what is needed (except existing *.wld file) is to create at least one *.aux.xml file with same file name as image and proper CRS definition (content as shortened example above). Then the file can be simply copied and renamed for all JPG/PNG files so for every file you have something like this:

image_01.jpg, image_01.jpg.aux.xml, image_01.wld

image_02.png, image_02.png.aux.xml, image_02.wld

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