Diver visibility measured with a compact scattering-attenuation meter (SAM) compatible with AUVs and other small deployment platforms

Michael S. Twardowski; J. Ronald V. Zaneveld; Casey M. Moore; James Mueller; Charles Trees; Oscar Schofield; Scott Freeman; Tyler Helble; Gerry Hong

doi:10.1117/12.603974

19 May 2005 Diver visibility measured with a compact scattering-attenuation meter (SAM) compatible with AUVs and other small deployment platforms

Michael S. Twardowski, J. Ronald V. Zaneveld, Casey M. Moore, James Mueller, Charles Trees, Oscar Schofield, Scott Freeman, Tyler Helble, Gerry Hong

Author Affiliations +

Proceedings Volume 5780, Photonics for Port and Harbor Security; (2005) https://doi.org/10.1117/12.603974
Event: Defense and Security, 2005, Orlando, Florida, United States

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.

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Michael S. Twardowski, J. Ronald V. Zaneveld, Casey M. Moore, James Mueller, Charles Trees, Oscar Schofield, Scott Freeman, Tyler Helble, and Gerry Hong "Diver visibility measured with a compact scattering-attenuation meter (SAM) compatible with AUVs and other small deployment platforms", Proc. SPIE 5780, Photonics for Port and Harbor Security, (19 May 2005); https://doi.org/10.1117/12.603974

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