Coastal Oceanography Using a Small AUV

Abstract

Bathymetry, current and CTD measurements in shallow waters on the continental shelf off the coast of Florida, using a small, mobile, autonomous underwater vehicle (AUV) platform equipped with a 1200kHz broad band ADCP, are described. Florida Atlantic University's AUV, the Ocean Explorer, which was used in the mission, is a 7ft long versatile, Gertler body which can perform pre-programmed underwater missions to a depth of 1000ft. At a speed of 1-2 m/s, it can perform missions over a period of several hours, collecting in-situ oceanographic data and storing it on an on-board data-logger. The vehicle may also carry a side-scan sonar or a small-scale custom turbulence measurement package or other instruments for subsidiary measurements. The versatility of the AUV allows measurement of oceanographic data over a substantial region, the motion of the platform being largely decoupled from that of the sea surface.In the missions of Dec. 5 and 11, 1997, 'lawn-mower pattern' AUV surveys were conducted over 1 km 2 regions on the east coast of Florida, north of Fort Lauderdale, at depths of 7m and 3m respectively in a water column where depth ranged from 10 -32m. During Dec. 5, the region was subjected to a cold front from the northwest. Local wind measurements show presence of up to 10m/s winds at temperatures of up to 10-15 0 C below normal for the time of the year. The fixed ADCP indicates occurrence of significant internal wave activity in the region. The data collected using the mobile AUV is utilized to develop a map of the bottom topography and examine current, temperature and density variations in the context of the background information from the fixed systems. The work described here is a significant step in the development of an autonomous oceanographic sampling network, illustrating the versatility of an AUV platform. The data collected during the missions described will form part of a bank for information on the impact of a cold front on shallow sub-tropical waters. We expect to repeat the missions during other such fronts.

Enhancement of the inertial navigation system for the Morpheus autonomous underwater vehicles

“…The heading is then evaluated as (2) where and represent pitch, roll, and heading in radians and and correspond to the two orthogonal field components expressed in the local-level frame.…”

“…Because of the viscosity of the sensors' liquid, the pitch and roll errors are characterized by their time lag and attenuation, and they can be significant if the instrument is subject to considerable vehicle motion, as implied from (1) and (2). In addition, the TCM2 is sensitive to local magnetic sources which can originate from the vehicle (e.g., batteries, motors and cables), or any external objects encountered in the vicinity (e.g., mines and cables).…”

Hybrid Motion Planning Task Allocation Model for AUV’s Safe Maneuvering in a Realistic Ocean Environment

“…Autonomous Underwater Vehicles (AUVs) have been discovered as the most cost-effective and expedient technology in carrying out the underwater missions over the past and coming years. They are largely employed for various purposes such as scientific underwater explorations [1], inspection and surveys [2], sampling and monitoring coastal areas [3], offshore installations and mining industries [4], etc. However, most of the available AUVs operate with a preprogrammed mission scenario while all parameters for entire mission should be defined in advance and operator's interaction is necessary issue.…”

Modular autonomous biosampler (MAB) — A prototype system for distinct biological size-class sampling and preservation

“…The last 10-15 years have seen a tremendous growth in the development and application of new sensor platforms, specifically autonomous and Lagrangian platforms [17] such as Autonomous Underwater Vehicles (AUVs) [3], [2], [7], [12], drifters, and ocean gliders and especially in the realm of integrated Ocean Observing Systems (OOSs) [9] [6], [15], [13]. Each platform enables advanced sampling further into unique subsets of these uncharted regions.…”