Enabling AUV mapping of free-drifting icebergs without external navigation aids

This paper documents improvements in the method for offline estimation of iceberg geometry as presented by Kimball and Rock [1]. The method removes the AUV´s inertial position from the equations, allowing the mission to be completed without ship-based navigation aids. This is a substantial operational advantage. Additionally, it differs from [1] in that it treats each sonar return individually, instead of abstracting multiple readings to a single point, removing a potential source of bias. Finally it reformulates the problem to simplify greatly the estimation optimization by reducing the number of needed estimation parameters. Together, these changes yield speed increases of roughly three orders of magnitude, with no loss in accuracy. The method is demonstrated via full simulation of an AUV operating around a free drifting iceberg. Additionally, an underwater sea cliff in Monterey Canyon is used as an iceberg surrogate to test the method on field data.