Horizontal mapping accuracy in hydrographic AUV surveys

Underwater vehicles are used in a wide range of tasks in various sectors. Cost-effective and accurate seabed surveying and mapping using autonomous underwater vehicles (AUVs) have been carried out for years in the offshore oil and gas sector. Much of the experience gained is now being benefited upon in new and challenging applications. One of the emerging AUV applications is hydrographic surveying (e.g. for creating nautical charts), particularly in waters shallower than 100 m. Key factors for mission-success include obtainable accuracy and resolution of the final digital terrain model (DTM), as well as the feature detection capability of the integrated system. This paper gives an in-depth discussion and analysis of the horizontal mapping accuracy achievable by integrated, state-of-the-art hydrographic AUV systems. The HUGIN 1000 AUV fitted with interferometric synthetic aperture sonar (SAS) is used as a case study, and the system accuracy as assessed in detail - starting from surface navigation, going all the way down to the acoustic seabed footprint. A discussion is given at the end on the feasibility of AUVs in terms of the minimum standards proposed by the International Hydrographic Organization (IHO).