Digital elevation models (DEM) and their derivatives (e.g., slope and aspect)
can indicate surface processes like lateral water flow, solar irradiation or erosion.
The simplest derivatives of a DEM are the slope and the aspect. The slope (or gradient) describes the measurement of the steepness, the incline or the grade of a surface measured in percentages or degrees.
The aspect (or exposure) generally refers to the direction to which a mountain slope faces.