Apr 20, 2017
Jolley Hall, Room 309
"Underwater Celestial Navigation Using the Polarization of Light Fields"
Adviser: Roger Chamberlain
Global-scale underwater navigation presents challenges that modern technology has not solved. Current technologies drift and accumulate errors over time (inertial measurement), are accurate but short-distance (acoustic), or do not sufficiently penetrate the air-water interface (radio and GPS). To address these issues, I have developed a new mode of underwater navigation based on the passive observation of patterns in the polarization of in-water light. These patterns can be used to infer the sun's relative position, which enables the use of celestial navigation in the underwater environment. I have developed an underwater polarization video camera based on a bio-inspired polarization image sensor and the image processing and inference algorithms for estimating the sun's position. My system estimates heading with RMS error of 6.02° and global position with RMS error of 442 km. Averaging experimental results from a single site yielded a 0.38° heading error and a 61 km error in global position. The instrument can detect changes in polarization due to a 0.45° movement of the sun, which corresponds to 50 km of ground movement, with 99% confidence. This technique could be used by underwater vehicles for long-distance navigation and suggests additional ways that marine animals with polarization-sensitive vision could use to perform both local and long-distance navigation.