Steven Lerner

High-resolution seafloor mapping using the DSL-120 sonar system: Quantitative assessment of sidescan and phase-bathymetry data from the Lucky Strike segment of the Mid-Atlantic Ridge

High-resolution, side-looking sonar data collected near the seafloor (∼100xa0m altitude) provide important structural and topographic information for defining the geological history and current tectonic framework of seafloor terrains. DSL-120xa0kHz sonar data collected in the rift valley of the Lucky Strike segment of the Mid-Atlantic Ridge near 37°xa0N provide the ability to quantitatively assess the effective resolution limits of both the sidescan imagery and the computed phase-bathymetry of this sonar system. While the theoretical, vertical and horizontal pixel resolutions of the DSL-120 system are <1xa0m, statistical analysis of DSL-120 sonar data collected from the Lucky Strike segment indicates that the effective spatial resolution of features is 1–2xa0m for sidescan imagery and 4xa0m for phase-bathymetry in the seafloor terrain of the Mid-Atlantic Ridge rift valley. Comparison of multibeam bathymetry data collected at the sea-surface with deep-tow DSL-120 bathymetry indicates that depth differences are on the order of the resolution of the multibeam system (10–30xa0m). Much of this residual can be accounted for by navigational mismatches and the higher resolving ability of the DSL-120 data, which has a bathymetric footprint on the seafloor that is ∼20 times smaller than that of hull-mounted multibeam at these seafloor depths (∼2000xa0m). Comparison of DSL-120 bathymetry with itself on crossing lines indicates that residual depth values are ±20xa0m, with much of that variation being accounted for by navigational errors. A DSL-120 survey conducted in 1998 on the Juan de Fuca Ridge with better navigation and less complex seafloor terrain had residual depth values half those of the Lucky Strike survey. The quality of the bathymetry data varies as a function of position within the swath, with poorer data directly beneath the tow vehicle and also towards the swath edges.Variations in sidescan amplitude observed across the rift valley and on Lucky Strike Seamount correlate well with changes in seafloor roughness caused by transitions from sedimented seafloor to bare rock outcrops. Distinct changes in sonar backscatter amplitude were also observed between areas covered with hydrothermal pavement that grade into lava flows and the collapsed surface of the lava lake in the summit depression of Lucky Strike Seamount. Small features on the seafloor, including volcanic constructional features (e.g., small cones, haystacks, fissures and collapse features) and hydrothermal vent chimneys or mounds taller than ∼2xa0m and greater than ∼9xa0m2 in surface area, can easily be resolved and mapped using this system. These features at Lucky Strike have been confirmed visually using the submersible Alvin, the remotely operated vehicle Jason, and the towed optical/acoustic mapping system Argoxa0II.

Quantitative seafloor characterization using a bathymetric sidescan sonar

Bathymetry and backscatter measurements from a 120-kHz phase-difference sonar are analysed in terms of statistical and spectral characteristics. Data from a multisensor, multiscale survey of the Juan de Fuca Ridge are compared across three distinct geological provinces: sediment pond, ridge flank, and axial valley. The detrended bathymetry follows a Gaussian distribution; the power spectral density can be approximately described by a power law. The composite multiscale power spectrum demonstrates a similar slope spanning a spatial frequency range from about 0.005 to 50 cycles/m, corresponding to a range of geological features from a few hundred meters down to several centimeters. The backscattering strength and grazing-angle dependencies agree with previous empirical studies; data from a sediment-pond region are shown to match theoretical predictions of the composite-roughness model. Histograms of the echo amplitude are characterized by a multimodal Rayleigh probability density function. For all analyses, the data show distinct differences among the three provinces. >

Acoustic and oceanographic observations and configuration information for the WHOI moorings from the SW06 experiment

Abstract : This document describes data, sensors, and other useful information pertaining to the moorings that were deployed from the R/V Knorr from July 24th to August 4th, 2006 in support of the SWO6 experiment. The SWO6 experiment was a large, multi-disciplinary effort performed 100 miles east of the New Jersey coast. A total of 62 acoustic and oceanographic moorings were deployed and recovered. The moorings were deployed in a T geometry to create an along-shelf path along the 80 meter isobath and an across shelf path starting at 600 meters depth and going shoreward to a depth of 60 meters. A cluster of moorings was placed at the intersection of the two paths to create a dense sensor-populated area to measure a 3-dimensional physical oceanography. Environmental moorings were deployed along both along-shelf and across-shelf paths to measure the physical oceanography along those paths. Moorings with acoustic sources were placed at the outer ends of the T to propagate various signals along these paths. Five single hydrophone receivers were positioned on the across shelf path and a vertical and horizontal hydrophone array was positioned at the intersection of the T to get receptions from all the acoustics assets that were used during SW06.

Towards image-based characterization of acoustic navigation

This paper examines the role of image-based navigation in the context of characterizing the standard long baseline navigation used by underwater vehicles for survey applications. Our work is based on looking at the displacement estimate that can be derived from registering overlapping imagery of the seafloor. Our approach is realistic in that it does not require large overlap and in that it can handle translational and rotational motions between image pairs in an unstructured terrain. We demonstrate our approach on a photographic survey conducted by the Argo towed vehicle covering several square kilometers off of Guam in the Pacific Ocean over a period of almost two months.

ExView: A Real-time Collaboration Environment for Multi-ship Experiments

New challenges in the area of experimental logistics, data visualization and data fusion are encountered in oceanographic research when the need to keep track of the location of multiple ships, moorings, gliders, drifters, and other platforms is combined with assimilating supporting data gathered off the Internet and inserted into the experimental framework. Showing that this can be done well is a start towards our being able to think of scientific expeditions on research vessels as deployable ocean observatories. Researchers at the Woods Hole Oceanographic Institution recently collaborated with the Rutgers University Coastal Ocean Observing Lab (COOL) and other members of the Shallow Water 06 experiment (sponsored by the US Office of Naval Research) in the creation of a new software tool called ExView. This experiment viewer software is a Web-based application that runs on ships and on shore. It enables coordinated, real-time collaboration between researchers employing a number of different research platforms involved in a large-scale experiment. During the SW06 experiment, logistics information and scientific reports associated with twenty-five principal investigators, six ships, eight gliders, three REMUS class AUVs, sixty-two moorings, two aircraft, and four drifting moorings were all made available to researchers in near-real-time over a three month time-period during the summer of 2006. A primarily wireless communications network comprising of HiSeasNet (satellite), SWAP (shipboard WiFi), SeaNet (INMARSAT-B), and the Global Internet was used to synchronize Websites (5 on ships, 1 on shore) so that all participants of the experiment could contribute and monitor platform locations, ship tracks, glider tracks, aircraft tracks, daily reports, weather information, CODAR imagery, satellite imagery, and ocean model results. A dynamic website was mirrored between all of the ships involved in the SW06 experiment. A map at the center of the web display showed location and tracks of all platforms (ships, moorings, planes, gliders, etc.) and the logistics-related information available from each of them. As ships wandered in and out of wireless range of each other, they updated each others Websites (even though Internet access might not have been available to the ship at that time). A shore-based website was also updated regularly by ships that had satellite connections back to the Internet. Participants on shore (and on each ship) were able to use the website to browse back in time to see the location and status of mobile platforms, science reports that were submitted each day, and data from a number of standard data sensors collected by each of the ships throughout the experiment. A shore-based team at the Rutgers University Cool Lab provided daily reports with graphics such as water temperature profiles, hurricane reports, satellite imagery, weather reports, wind speed profiles, etc. They also provided an analytic analysis of these elements and how they related to the current experiment plans. In addition, Rutgers staff used the ExView application to monitor the locations of their fleet of gliders and steer them to avoid moorings and other fixed and mobile assets in the area. An emerging technology called delay-tolerant networking (DTN) is being examined for inclusion in the ExView software suite. The current DTN design promises tighter integration of wireless technologies and the development of new algorithms capable of routing data via mobile platforms based on available bandwidth, remaining battery power, platform location, data priority, etc. These characteristics will be incorporated into new optional routing algorithms that will be developed in the future as part of DTN. The successful 3-month use of ExView shows how a novel, near-real-time, Web-based application can be used to improve access to logistics information about a collection of ships, other research platforms, investigators, data sensors, and related data sources. It also demonstrates how these assets can be joined together for a relatively short period of time to form something that might be considered a deployable ocean observatory.

A modular Gigabit Ethernet backbone for NEPTUNE and other ocean observatories

Ethernet is the most popular technology used for local area networks (LANs). Recently, Gigabit Ethernet (GbE) technology has successfully competed with SONET and other legacy alternatives such as ATM and frame relay for metropolitan area network (WAN) implementations. This paper describes a modular ocean observatory node design resulting from design activities of the NEPTUNE observatory data communications team. Internal node modules based on Gigabit Ethernet, point-to-point wave division multiplexing (WDM) and TCP/IP (Internet) protocol technologies are employed to define communications building blocks used in the design of the NEPTUNE regional scale ocean observatory communications system and are also applicable to coastal, buoyed and autonomous observatory nodes.

4DGeoBrowser : a web-based data browser and server for accessing and analyzing multi-disciplinary data

Abstract : This report describes the 4DGeoBrowser software system. The GeoBrowser is a web-based application developed at the Woods Hole Oceanographic Institution by Steven Lemer and Andrew Maffei. It has been designed with the goal of creating, accessing, and analyzing repositories of oceanographic datasets that have been generated by investigators in differing scientific disciplines. Once the information is loaded onto a Geobrowser server the investigator-user is able to login to the website and use a set of data access and analysis tools to search, plot, and display this information. GeoBrowser servers are also capable of processing commands that are submitted remotely via HTTP URLs or email. Scientists are able to use this capability to make calls to the GeoBrowser server and generate click-able maps, tables of URLs, and customized HTML pages. These can then be used to enhance websites associated with scientific projects. Examples of supporting scientific website functionality that includes time series plotting, data delivery by email, geo-spatial plotting of interdisciplinary data, map-based search capabilities and other functionality are presented in this report. The report includes examples of GeoBrowser application websites, a user manual, and a reference guide. In addition, the concept of Electronic Index Cards (EICs) is presented.

At Sea Test 2 deployment cruise : cruise 475 on board R/V Oceanus September 22 – 26, 2011 Woods Hole –Woods Hole, MA

Funding was provided by the National Science Foundation nthrough the Consortium for Ocean Leadership

Design and Construction of a Polar Remote Interactive Marine Observatory (PRIMO)

A seafloor marine observatory is under development for deployment in Antarctic coastal waters to study and monitor the physical, biological, and biogeochemical processes as a function of global climate change. This observatory will consist of an instrument package on the seafloor 3.5 km from shore in 130 m of water connected the U.S. base Palmer Station by electro-optical cable, providing the capability for internet-based teleoperation by educators, students, and scientists from anywhere in the world