Terrain referencing for autonomous navigation of underwater vehicles

A terrain aided navigation correction system has been developed for use with the autonomous underwater vehicle (AUV) Autosub 6000. This system allows drift in dead-reckoning navigation to be estimated by matching bathymetry observed in multibeam echosounder (MBE) data to a reference map. The reference map consists of a single line of bathymetric data, one swath width across, spanning the operational area of a survey mission. This map is collected by Autosub prior to undertaking the survey. This paper presents a discussion of the biases in typical AUV navigational sensors and their influence on navigation on a map that is created in-mission by a submersible. Based on this discussion a filter has been implemented and has been used to analyse the navigational errors accumulated during an Autosub 6000 survey mission and computational limitations for realtime application are assessed.