טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentVainiger Adi
SubjectUnderwater Wide Field Tomography of Sediment Resuspension
DepartmentDepartment of Electrical Engineering
Supervisor Professor Yoav Schechner
Full Thesis textFull thesis text - English Version


Abstract

Sediment resuspension is the transport of previously settled particles from the seafloor back into the overlying water. Sediment resuspension affects processes in nature as nutrients recycling and water quality. There is a gap of knowledge of biological sediment resuspension events, stems from a lack in methods to quantify them and estimate their effects on the environment. Measuring these abrupt and spatially varying events is challenging. Existing in-situ approaches are very localized.


We present a novel wide-field imaging approach to optically sense underwater sediment resuspension events from a distance. It uses wide-field multi-directional views and diffuse backlight. Our approach algorithmically quantifies the amount of material resuspended and its spatiotemporal distribution in three-dimensions (3D).  The suspended particles affect the radiation that reaches the cameras, hence the captured images. By measuring the radiance during and prior to resuspension, we extract the optical depth on the line of sight (LOS) per pixel. Using computed tomography (CT) principles, the optical depths yield estimation of the extinction coefficient of the suspension, per voxel. The suspended density is then derived from the reconstructed extinction coefficient.


This thesis elaborates on the concept of the proposed approach, including a theoretical formulation, computer simulations, engineering of an optical CT system, algorithm and empirical validation results.