This thesis advances wearable outdoor augmented reality (WOAR) research by proposing novel visualisations, by consolidating previous work, and through several formal user studies. Wearable outdoor augmented reality combines augmented reality (AR) and wearable computing to enable novel applications. AR allows the user to perceive virtual objects as part of their real environment. Using wearable computers as a platform for AR allows users to see the real and the virtual world combined in a mobile environment. This combination enables new and exciting applications that bring with them new challenges for interface and usability research. The research described in this thesis advances the field of WOAR research by developing a WOAR version of a commercial road stakeout application. This case study makes possible the first formal direct comparison of the performance of a WOAR application and its conventional counterpart. Road stakeout is the process of locating points in the real world and marking them with stakes. This process is not only relevant for road construction, but also to construction and surveying in general. AWOAR stakeout application can visualise stakeout targets on their location in the real world, while conventional stakeout systems can only guide users to these locations using indirect displays. The formal comparison found significant differences in performance, and showed that the WOAR system performed twice as fast at the same accuracy level as the conventional system. The study also identified a number of usability issues and technical problems related to WOAR systems that still need to be overcome. The thesis examines usability problems of the WOAR road stakeout application in detail, proposes solutions, and compares their efficiency in formal user studies. The basic stakeout tasks are navigating to a target location and then placing a stakeout pole on that location. Original research in the fields of directional interfaces and depth cues determined solutions for efficient navigation and pole placement in the WOAR stakeout application. Further, the presented work includes explorative implementations of obscured information visualisations. The thesis proposes interaction with artificially transparent stakeout poles and hands, and examines their feasibility with respect to perceptual and technical issues. A visualisation of a road model investigated the preservation of context while automatically providing detail when needed. The thesis presents working WOAR implementations of navigation and depth cue support, a road model visualisation, and an artificially transparent stakeout pole. In conclusion, the thesis consolidated WOAR interface research and extended the field with empirical research. The presented research is the first that allows a WOAR application to compete directly with a commercial conventional system, demonstrating the strong potential that WOAR systems already have.