Most geological knowledge is applied in a spatial context.
Thus, in order to consider the implications of geologic processes on humans or humans on their geologic environment, you must define that context. The tools which we use are aerial photographs, maps, and site-specific documents. Aerial photographs are the base source of information for all modern maps. Sophisticated plotters generate topography from the parallax, or apparent difference in spacing with differing elevation, of aerial photographs. Vegetation, streams, and human artifacts such as buildings and roads are interpreted from the photos.