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I have encountered a GeoTIFF raster files with EPSG:4326 (WGS84), i.e. no projection defined! Is this normal? I would expect raster to be in Projected Coordinate System. Raster is a grid of pixels so I expected this would be defined in the plane.

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The geotiff you describe does have a projection - it's called Plate Carre. As noted in the link this is neither equal area nor conformal, so it's usefulness is very limited. On the other hand, it is very easy to produce, since the lat/lon of a pixel is trivially derived from the pixel indices.

As to your question "is this normal?", I'm not sure how to answer that. It's certainly well-defined and conforms to the geotiff specification. I'm not sure I've personally ever seen a geotiff defined this way, but that's possibly because of the nature of the geotiffs I work with. If your question really is how common is this usage, perhaps someone else can provide an answer.

  • "The geotiff you describe does have a projection..." - how did you found out? Can you please post a link or resource? I think that EPSG:4326 doesn't contain any projection. In QGIS it is mentioned among Geographic Coordinate Systems, so it should have only datum, no projection. – Tomas Jul 20 '13 at 15:32
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    EPSG:4326 itself is not a projection, as you note. However, a geotiff, such as yours, in which the pixels correspond to equally spaced bands of latitude and longitude meets the definition of a Plate-Carre projection, at least as far as I understand it. You might want to run gdalinfo on your geotiff and post that with your question. That will insure you receive the most accurate possible answer with respect to your specific geotiff – Llaves Jul 20 '13 at 16:25
  • Here is a discussion about the projection of an apparently unprojected WGS84 layer: gis.stackexchange.com/questions/73576/… – multigoodverse Oct 23 '13 at 8:51

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