Creating a shade layer (not shaded relief)

Discussion created by Akutan on Mar 25, 2013
Latest reply on Apr 1, 2013 by Akutan
Ok, I've tied searching for several days and not come up with a solution.  I am trying to create a raster that depicts the area upon the ground on which shade is being produced the tree canopy.  Ultimately a series of these layers could be added together to determine how much a point on the ground is shaded during the day.  Unfortunatly the standard hillshade model doesn't project the shade onto the surface of the ground but rather onto the surface of the input file.  For example, consider a tall tree surrounded by shorter trees.  The shorter trees and the tall tree itself would naturally shade the area directly under the tall tree.  However, using the standard hillshade model every canopy-shade layer would show the top of the tall tree being illuminated.  When all of the canopy-shade layers are summed to produce the final shade layer, the location under the tall tree would show little, if any shadowing because the shadowing is being applied to the tree canopy surface and not onto the ground. This is illustrated in the attached JPG.  The area where the star is located is not being modeled as being shaded because it is directly underneath the tall tree.

Any suggestions would be helpful.

Thank you