Calculating slope from a DEM

[EmmaDeary]

Hi

I have downloaded a tile of Alaska from GOTOP30 (1km resolution) and I need to calculate slope. However when I do calculate percent slope the values are in millions when the elevation for that point is only say 1200m. I have tried all the projected equal area/distance projections that I can find listed in Arcmap but that does not seem to change the values when I calculate slope. Someone has suggested that I need to make sure the projection has the horizontal distance in meters but I do not know how to find this information and then change it.

i would be very grateful for any help.

Emma

[BrianDudek]

While I am not familiar at all with GOTOP30.  I would presume you need to make sure to use a projection that goes along with the inherent elevation measurement values in GOTOP30.  I would imagine they are in feet or meters.  So try to project the image into stateplane (feet) and run the slope function.  If that doesn't work try a UTM projection (meters) and run slope again.