LASER LINE SCAN - A Microbathymetric Laser Imaging System

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Contents
Functional Description	Specifications
Development Pictures/Movies/Data	People
Sponsors	Publications

Functional Description
The submersible laser bathymetric (LBath) optical system is capable of simultaneously providing visual images and generating bathymetric maps of the sea floor with centimeter spatial and depth resolution. The system operates at roughly 10 m above the sea floor and builds a bathymetric image by taking successive swaths of the sea floor as the system moves through the water aseither a towed or an autonomous underwater vehicle (AUV). The system has been designed with the specific purpose of remotely identifying semi-submerged mines in turbid coastal waters.

General Specifications
The pulsed laser beam scans the sea floor in one dimension while being synchronously imaged by a high speed linear CCD camera. For every laser pulse generated, a linescan image of the sea floor is captured by the CCD camera providing a complete one-dimensional image of the spatial energy distribution spectrum surrounding the laser target spot. The energy distribution profile of the laser beam on the sea floor facilitates identification of the target spot position against a high backscatter contribution from in-water scattering. Bathymetric data is obtained by triangulation between the target spot, laser scanner and camera which are separated by a small distance (~0.8 m). Depth is calculated by measuring the laser beam angle and its corresponding target position imaged on the CCD. The in-line geometry of the scanner sweep and the camera field-of-view provides extended range capability.

People

Principal Investigators	Jules Jaffe
Chief Engineer	Karl Moore
Electrical Engineer	Ben Ochoa
Mechanical Engineer	Fred Ulhman - Hydrodynamic aspects, mechanical design/fabrication.
Software Development	Ben Ochoa - Data acquisition, instrument control, GUI
Graduate Students	Dave Zawada
Lab Assistants	Mathew Diebolt

Development Pictures/Movies/Data
To view the movies through the web browser, Quicktime plugin is required. To save the movies to your local machine right-click (Shift-click) the .mov or .avi links.

Pictures
Deployment	Tow1
LBath on Deck	Tow2

Data

A mine-like object imaged on the SIO pier Movie Download: .avi

A sandwave imaged in May 1999 off of Lee Stocking Island, The Bahamas Movie Download: .avi

Turtle grass imaged in May 1999 off of Lee Stocking Island, The Bahamas Movie Download: .avi

Demo of how the LBath scans. Movie Download: .avi

Fields of stromatolites (pillars of CaCO3 secreted by cyanobacteria)

A map of sea surface height obtained by suspending the system above the sea surface, looking down

PDF of the Laser Line scan poster

Publications

Moore, K.D., J. S. Jaffe and B. L. Ochoa, “Development of a new underwater bathymetric laser imaging system: L-Bath,” Journal of Atmospheric and Oceanic Tech. Vol. 17, No. 8, pg. 1106-1117 (2000).

Moore, K.D. and J.S. Jaffe, "Time-evolution of high-resolution topographic measurements of the sea floor using a 3D laser line scan mapping system," IEEE Journal of Oceanic Engineering

Sponsors

Office of Naval Research