Human beings live and work in large and complex environments. It is often difficult for individuals to perceive and understand the structure of these environments. However, the formation of an accurate and reliable cognitive map, a mental model of the environment, is vital for optimal navigation and coordination. The need to develop a reliable cognitive map is common to the average individual as well as workers with more specialized tasks, for example, law enforcement or military personnel who must quickly learn to operate in a new area. In this dissertation, I propose the use of a wearable computer as a platform for a spatial cognition aid. This spatial cognition aid uses terrain visualization software, GPS positioning, orientation sensors, and an eyeglass mounted display to provide an overview of the surrounding environment. While there are a number of similar mobile or wearable computer systems that function as tourist guides, navigation aids, and surveying tools, there are few examples of spatial cognition aids. I present an architecture for the wearable computer based spatial cognition aid using a relationship mediation model for wearable computer applications. The relationship mediation model identifies and describes the user relationships in which a wearable computer can participate and mediate. The dissertation focuses on how the wearable computer mediates the users perception of the environment. Other components such as interaction techniques and a scalable system of servers for distributing spatial information are also discussed. Several user studies were performed to determine an effective presentation for the spatial cognition aid. Participants were led through an outdoor environment while using different presentations on a wearable computer. The spatial learning of the participants was compared. These studies demonstrated that a wearable computer can be an effective spatial cognition aid. However, factors such as such as mental rotation, cognitive load, distraction, and divided attention must be taken into account when presenting spatial information to a wearable computer user.