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Proceedings Paper

Diver visibility measured with a compact scattering-attenuation meter (SAM) compatible with AUVs and other small deployment platforms
Author(s): Michael S. Twardowski; J. Ronald V. Zaneveld; Casey M. Moore; James Mueller; Charles Trees; Oscar Schofield; Scott Freeman; Tyler Helble; Gerry Hong
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Paper Abstract

An appropriate determination of water clarity is required by defense and security operations assessing subsurface threats compromising harbor and coastal security. For search and inspection operations involving divers, underwater imaging, and electro-optical identification (EOID) systems such as laser line-scanners, the key environmental parameter needed is the optical attenuation coefficient (directly related to diver visibility). To address this need, a scattering-attenuation meter (SAM) measuring attenuation and diver visibility was developed for integration on new compact surveying platforms such as ROVs and the REMUS and glider AUVs. The sensor is compact (18X8X6 cm3), low power, robust, and hydrodynamic with a flat sensing face. The SAM measures attenuation using a novel dual-scattering approach that solves the paradox of making high-resolution attenuation measurements over the long pathlengths required for natural waters with a compact sensor. Attenuation and visibility data is presented from San Diego harbor in coordination with video images of bottom topography collected with a REMUS vehicle, from around New York harbor with a SAM mounted in an autonomous Slocum glider, and from Narragansett Bay. Results show that 1) visibility and/or attenuation in harbor and coastal regions can change rapidly over small scales (meters), especially near the bottom, 2) turbid bottom nepheloid layers are common, 3) typical visibility and/or attenuation levels fall in a range where knowledge of visibility and/or attenuation can be essential in the decision making process for security operations, and 4) attenuation is a significantly more accurate proxy for diver visibility than backscattering.

Paper Details

Date Published: 19 May 2005
PDF: 10 pages
Proc. SPIE 5780, Photonics for Port and Harbor Security, (19 May 2005); doi: 10.1117/12.603974
Show Author Affiliations
Michael S. Twardowski, WET Labs, Inc. (United States)
J. Ronald V. Zaneveld, WET Labs, Inc. (United States)
Casey M. Moore, WET Labs, Inc. (United States)
James Mueller, San Diego State Univ. (United States)
Charles Trees, San Diego State Univ. (United States)
Oscar Schofield, Rutgers Univ. (United States)
Scott Freeman, WET Labs, Inc. (United States)
Tyler Helble, SPAWAR (United States)
Gerry Hong, SPAWAR (United States)

Published in SPIE Proceedings Vol. 5780:
Photonics for Port and Harbor Security
Michael J. DeWeert; Theodore T. Saito, Editor(s)

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