Why the default value of the azimuth in the hillshade is 315?
As I understand, the hillshade map represent the shade that the sun makes form specific location
1. Why the default azimuth is 315? It should be 90 to represent the East
2. What does of the values in the hillshade represent?
Please, see the attached image
As I understand, the hillshade map represent the shade that the sun makes form specific location
1. Why the default azimuth is 315? It should be 90 to represent the East
2. What does of the values in the hillshade represent?
Please, see the attached image
It's been 15 or more years since I learned this in basic GIS/Geography courses in college, though, so not sure but it is documented in academic science materials or possibly Cartography educational resources.
It has to do with how the human eye perceives shadows and depths and putting the light source from the North/NorthWest has the effect to put shadows at the base of hills/ridges/mountains and thus, they are not depressions, but appear as extrusions.
If your goal is to iterate and change the sun's position to simulate real effects of shadows for a modeling exercise, then the default value should be changed to simulate the sun's position in the sky.
If it's to make a "pretty shaded relief map" keeping it at the default generally produces the best looking Hillshade output.