I am a beginner usign ArcGis, i downloaded two geotiff with the same cellsize and with the same GCS ( GCS_WGS_1984) but it seems that the two images don't perfectly overlay. Looking at the extent of these images i noticed that:


extent left: -180,008333334 extent right: 180,008333275

While the other one:


extent left: -180 extent right: 180,000033063

So for both the right extent is greater than +180 while for the first one the left extent is lower than -180. I know that the problem is related to the coordinate system but i can't understand where i make the mistake


ArcGIS defines the coordinate system of the Dataframe (the canvas) using the CRS of the first dataset you import into it. In your case the first raster.

If any additional dataset is in a different CRS it will try to reproject it on the fly (if it needs additional information to do that it will tell you) or if there is no CRS embended in the dataset it warn you again.

My guess is that you haven't done anything wrong; whoever made these datasets, it wasn't part of his specs.

For a possible 'workaround' there was a similar question here some time ago: Aligning two non-coincident equi-resolution raster grids in ArcGIS Desktop?

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