Expanding the small AUV mission envelope; longer, deeper & more accurate

Small, man-portable AUVs now carry out engineering and geophysical survey tasks where previously boat-mount, towed or ROV-mounted sonars would have been required. The commercial use of low-logistics AUVs in the offshore survey industry is expanding rapidly, with several companies now operating small survey AUVs worldwide. This paper describes some of the advances in vehicle and payload technology which have enabled the uptake in commercial survey roles such as pipeline inspections, rig move surveys, harbor inspections and environmental work. Modular AUV design has enabled the continued expansion of the small-AUV envelope of operations: extending time on-site with field-swappable batteries; enhancing deliverables with multi-sensor configurations such as swath bathymetry and sub-bottom profiler; and enabling longer mission durations with multiple battery configurations. One limitation to AUV operations has been the accuracy of navigation during extended submerged missions. This has led to the development of subsea position aiding techniques such as inverted USBL to improve in the accuracy of longer missions and deeper water surveys (up to 1000m). Current AUV system performance and capabilities are illustrated using examples of side scan, swath bathymetry and sub-bottom data from a widely used low-logistics survey AUV, the Gavia Surveyor.