Date of Award

2019

Degree Type

Thesis

Degree Name

Master of Science in Ocean Engineering

Department

Ocean Engineering

First Advisor

Lora Van Uffelen

Abstract

The Kongsberg Seaglider M1 is a commercially available autonomous under- water vehicle (AUV) primarily used as a platform for oceanographic measurements of salinity, temperature, and oxygen. The Seaglider currently uses two different dead-reckoned solutions, the glide slope model (GSM) and the hydrodynamic model (HDM), to provide a localization solution for each dive. While the accuracy of these solutions was not previously known explicitly, for the purposes of oceanographic profiling they were generally deemed sufficient. As the platform matures, there has been a growing interest in expanding its application and measurement capabilities. With some of the desired new applications, such as using the Seaglider as a moving acoustic receiver in acoustic tomography, comes a need to quantify and improve the localization accuracy of the vehicle.

This project sought to quantify the accuracy of the two localization solutions currently in use, investigate the effects of additional inertial measurements on the accuracy of such solutions, and identify potential opportunities for improvement to vehicle localization. To accomplish these goals, a Seaglider was instrumented with an inertial measurement unit (IMU) and tracked on the Dabob Bay acoustic tracking range. The acoustic track from the range was considered a ground-truth and used to evaluate various localization solutions. Error metrics were developed to quantify and compare the accuracy of the different localization solutions.

Results indicated the Seaglider’s GSM solution is significantly more accurate than the HDM solution; while additional inertial measurements did not improve the accuracy of these solutions. From the collected data, sources of error in the two main localization solutions were identified, as well as their expected magnitude. Results were then used to make recommendations for development of an improved localization solution.

Available for download on Friday, July 31, 2020

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