I have a DEM of a the bedrock surface beneath a glacier and what I want to do is subtract the mean angle of the valley walls on the left and right side of the glacier along this line. I have a line that divides the glacier into a left and right side (the brown dotted points). Any suggestions on how to do it efficiently?
b) Buffer that line (the distance you are interested in) using left and right. Here you'll end up with two separate polygons (say, lineLeft and lineRight).
c) Using Extract by Mask (you must have the SpatialAnalist license), extract the DEM raster with lineLeft and lineRight. You'll end up with two rasters (say, demLeft and demRight).
d) Apply the Slope tool to both rasters, and you'll have the slope angle on both sides (two new rasters will be created)
e) Then for each of the new rasters, check their properties and their stats will be under the 'Source' tab.