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I have a elevation raster (1 arc second) downloaded from USGS site. Before adding it to ArcMap I changed the display units to meters.The projection system for this raster is GCS_1983. When I use the slope tool under the spatial analyst tool , it is unable to create the slope layer.The data type for the image is floatng.What could be possibly be wrong here.

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Even after reprojecting it I get the same error. enter image description here

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The cell size is 9.25925925930002e-005 –  Senthil Apr 28 '13 at 21:22
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You need to do more than change the display units. You need to reproject the raster to a projection that uses metres and rerun the slope analysis. –  Fezter Apr 28 '13 at 23:11
    
The title says "Error" but no error seems to be mentioned in the question. –  PolyGeo Apr 29 '13 at 8:38
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marked as duplicate by Fezter, Aaron, Aragon, whuber Apr 29 '13 at 14:33

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

1 Answer

Despite changing the display units, your raster still is still using a Geographic Coordinate System. Trying to run a slope analysis on such data is invalid. Slope (rise/run) doesn't make sense with degrees as the unit because the distance of 1 degree at the equator is greater than 1 degree near the poles.

You will need to reproject your raster to a coordinate system that uses metres as the units.

Re-run your slope analysis on the new data and you should be fine.

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How could I find which UTM zone for the raster to be reprojected. –  Senthil Apr 28 '13 at 23:53
    
Even after reprojection it doesnt help it... –  Senthil Apr 29 '13 at 1:19
    
What error message are you getting? –  Fezter Apr 29 '13 at 1:22
    
What projection did you use? –  Fezter Apr 29 '13 at 1:23
    
NAD 1983 UTM Zone 14N.The error is same as above in the original question here. Display units are in meters. Anything else I am missing here. –  Senthil Apr 29 '13 at 1:25
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