Autonomous mapping with AUVs using relative terrain navigation

In autonomous mapping surveys the autonomous underwater vehicle (AUV) cannot rely on receiving position aiding from a surface vehicle or any other external infrastructure. The AUV can however use any payload sensor to restrict the position error drift in the navigation system. In this paper we consider how to use the terrain in a pre-surveyed baseline to bound the drift in the estimated AUV position when the baseline is revisited later in the mission. This is done through terrain navigation updates relative to the baseline terrain model. Using off-line real data from a HUGIN AUV equipped with a HISAS 1030 interferometric synthetic aperture sonar, the concept is shown to work, and adequate mapping quality is obtained without the need for external aiding, except possibly during the initial surveying of the baseline.