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I have a very large high resolution raster map that is a tiff file that I usually work with in Photoshop. I would like to be able to use it with ArcGIS/QGIS but am not sure how I can define the projection or if that is possible.

PolyGeo
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user1209945
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  • the first question is about if your image is already georeferenced or not. Have a look to this question: https://gis.stackexchange.com/questions/18672/how-to-determine-if-a-tiff-is-georeferenced-or-not/18673. If it is not, then you need to georeference it. The procedure is very similar to georefence old scanned maps, here a tutorial: http://www.qgistutorials.com/en/docs/georeferencing_basics.html – Marco Mar 09 '18 at 22:34
  • The selection of a projection is a more complex question because involves assessing the use you want to give to the image, the extension of the map and the nature of the information you are working with. BTW, what is a "very large high resolution" today? In photoshop the size of the whole image matters, but in GIS it could be more important the size of the pixel in reallity and the nature of the information you can use to georefence the raster, a city? a road? a house? a colored square 25x25 cm? Tell us more and it would be easier to help you – Marco Mar 09 '18 at 22:45
  • Thanks! I think the georeferencing tutorial might be what I need. The image is a world map and I generally work with countries/admin regions. – user1209945 Mar 09 '18 at 23:01
  • A world map is a bit challenging regarding the choise of the right projection, out of my daily work. Probably, it was produce using a projection and it is better to know which one. This is a quite common question here. Here a nice reading about it: http://www.viewsoftheworld.net/?p=752 – Marco Mar 09 '18 at 23:12

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Yes it is possible. you can georeference it with any GIS software. But is the file is very large, georeferencing may take very long so it will be better to generate a tiff world file. (.tfw)

neogeomat
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If you want to edit it im photoshop and keep the georreference, you must configure photoshop to open with Piramid structure your image or you will loose the image georreference. the safer way is to georreference again the image after photoshop edit.

Luis Felipe Fragoso
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