Robust Methods of Magnetic Navigation of Marine Robotic Vehicles * *Funding: This Research Was Supported in Part by the European Project Wimust (Ga No. 645141) and the Portuguese Fct Program [Pest-Oe/Eei/La0009/2011]. The Authors Gratefully Acknowledge the Sponsorhip of the South Korean Agency for Defense Development Under a Collaborative Research Agreement Between Kaist and Ist.