This unit considers digital elevation models (DEMs) as one way of representing surfaces. It describes how DEMs are created and used, particularly in hydrology. Approaches for estimating elevation, slope and aspect, and for determining drainage networks are presented, along with a discussion of issues that may arise when automatically determining drainage networks from DEMs.

This unit discusses fractals as a framework for understanding the way cartographic objects change with generalization or changes in scale. It presents a brief history and introduces introductory concepts related to fractals, including scale-dependence, self-similarity and scaling.