Underwater Glider Terrain Relative Navigation for use in Surface Denied Regions
Brian Claus, Woods Hole Oceanographic Institution, Woods Hole, MA, United States and Ralf Bachmayer, Memorial University of Newfoundland, St John's, Canada
Abstract:
Autonomous underwater gliders have proven their utility to gather a wide range of measurements in a challenging environment. Their increasing adoption rates by scientific institutions and government organizations globally are a testament to this fact. However, operational gaps still exist in regions where surface access is denied due the inability of the vehicle to surface and acquire GPS updates to reduce the error of the localization estimates.Prior work by the authors has derived a terrain aided navigation algorithm developed for a Slocum Electric underwater glider. The algorithm makes use of the vehicle's dead-reckoned navigation solution, onboard altimeter and a local digital elevation model (DEM) to compute bounded location estimates independent of surface access. An evaluation of the method was performed through post-processing location estimates from 12 km of field trials in 2010 and 91 km of trials in 2012 which took place in the glacial fjord of Holyrood Arm, Newfoundland, overlapping a previously collected DEM. These results suggested the ability of the algorithm to maintain bounded error location estimates with a RMS error of 33 meters in the 2010 trials and 50 meters in the 2012 trials. These errors are contrasted with a dead-reckoned error of 900 meters in the 2010 trials and 5.5 km in the 2012 trials. These trials were followed by online open loop location estimates in 2014 for which RMS errors of 76 and 32 meters were obtained during two, hour long trials. The dead-reckoned error for these same trials was 190 meters and 90 meters respectively.The preliminary results of this method are promising but have been limited to a single region. To extend the methodology this work examines the suitability of other applicable ice covered regions such as the Antarctic as well as high ship traffic areas such as the Gulf of Mexico through archived glider data. Additional future areas of application include the Chukchi and Beaufort Seas and Davis strait.
