Date of Award

8-2025

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

School

Ocean Science and Engineering

Committee Chair

Dr. Gero Nootz

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Dr. Anand Hiroji

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Dr. Johnson Oguntuase

Committee Member 3 School

Ocean Science and Engineering

Committee Member 4

Dr. Leonardo Macelloni

Committee Member 4 School

Ocean Science and Engineering

Committee Member 5

Dr. Fraser Dalgleish

Abstract

This dissertation presents novel algorithms to improve the mapping capabilities of a 360-degree underwater Pulsed Laser Line Scanner LiDAR (PLLS-360°). Due to its 360° field-of-view (FOV), the PLLS-360° is a compact full-waveform omnidirectional imager suitable for seafloor mapping, underwater asset inspection, object detection, ice-sheet mapping, and construction progress monitoring. The proposed methodology includes an improved waveform fitting technique for saturated waveform recovery, detection array response correction, radiometric corrections, and fusion of LiDAR and sonar bathymetric datasets. The first part of this dissertation assesses the LiDAR’s performance and describes how the data for this unique 360° FOV architecture is processed. The processing entails correction of the LiDAR measurements for detector array characteristics, geometric spreading of returned signals, light attenuation in water, and AUV’s motion and position to improve the visualization of underwater 3D scenes. The second part presents a novel method for recovering saturated waveforms recorded by the PLLS-360°. Waveform saturation sometimes occurs from field measurements due to the receiver-target distance and wide intensity range exceeding the receiver dynamic range. This is more likely in the PLLS-360° compared to other underwater systems due to its unique architecture that allows it to record signal returns in all directions. This dissertation efficiently recovers the ideal peaks of the saturated PLLS-360° measurements through novel pre-processing steps such as saturated waveform sample removal and selection of waveform relevant part, which are further modeled using several mathematical models. The final part of the dissertation presents a suitable fusion technique for the PLLS-360° LiDAR and the sonar bathymetry, both acquired from the Iver3 AUV. The proposed weighted fusion of the bathymetric surfaces applies a slope constraint on structures in the boundary area of the LiDAR bathymetry to preserve the details of the features for a more accurate application of the fused bathymetry for navigation.

ORCID ID

https://orcid.org/0000-0001-5350-194X

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