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I'm trying to overlay a shapefile into a raster. The raster has no defined projection but it's a global raster with extent 0, -1800 : 3600, 0. I tried "on the fly CRS" transformation and followed the projection of my shapefile, and yeah they appeared together but with wrong position. My mistake here is that 3600 is read as 3600 degrees (I think), thus the length became 3600 (the resolution should be 0.1 degrees).

Can I change the extent and resolution when I reproject my raster? and how to change the extent and resolution?

The raster file is in .PNG by the way.

  • You could georeference it, the instructions are different depending on what software you're using. Please edit your question to indicate what software you have. Depending on what format the image is it might have a world file (or not, but you could create one) in this format: webhelp.esri.com/arcims/9.2/general/topics/…, what image format do you have? – Michael Stimson Mar 31 '15 at 4:39
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Apart from georeferencing, you could use gdal_translate to define the extent and CRS of the raster. In QGIS, you can access gdal-translate with Raster -> Conversion -> Translate.

Choose Input Layer from Canvas, Output file (using a different name), Target SRS should be set to EPSG:4326.

Then click on the pencil next to the last input form to complete the command:

-a_ullr ulx uly lrx lry:
    Assign/override the georeferenced bounds of the output file. This assigns georeferenced bounds to the output file, ignoring what would have been derived from the source fie.

-a_ullr -180 90 180 90 should be the right values.

  • Thanks man!!! It has a batch processing as well!!! Thanks a lot. I'll just play with the ulx uly because my raster got flipped. I was reading at the wrong command, i was looking at gdalwarp before posting the question here. Really, many thanks!!! – din Mar 31 '15 at 9:13
  • gdalwarp -te might work as well. – AndreJ Mar 31 '15 at 10:02
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Since your using QGIS you can use the Georeference tool on the raster file. The tool is found in menu Raster > Georeferencer. If you don't have have menu, search for it in the menu Plugins > Menage and Install Plugins ....

For help on the plugin check:

http://docs.qgis.org/1.8/en/docs/user_manual/plugins/plugins_georeferencer.html http://www.qgistutorials.com/en/docs/georeferencing_basics.html

BTW I can recommend the Helmert transformation type under transformation settings.

  • Thanks this one works. I actually wanted to see the process and will now try to work on automating it =D cheers! – din Mar 31 '15 at 9:06

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