Solving Wakulla Springs Underwater Mysteries

Using GPS to map FloridaÕs underground caverns
Located in the Woodville Karst Plain stretching south from Tallahassee to the Gulf of Mexico, Florida’s Wakulla Springs is one of the largest and deepest freshwater springs in the world. It is also a gateway into one of the longest underwater cave system in the United States, a system that remained largely unexplored until recently. Soon, however, thanks to one of the world’s most extreme scientific and exploration-related diving projects ever undertaken, visitors to Wakulla Springs State Park will be able to take a virtual tour through the Spring’s huge underwater labyrinth. Using such cutting-edge technology as a 3D Digital... (read more)
2008-01-01 01:00:00

AUV-based 3D Chirp Sub-bottom Profiling

Offshore Diamond Mining Applications
During the 1990s De Beers Marine identified a major business opportunity in radically improving its geological modelling capability. It set up a project to deliver the necessary geophysical systems and the team soon saw potential in integrating the company’s future development ideas for Chirp sub-bottom profiling sonar and sediment characterisation with the stability and accuracy of AUVs. The result was an ultra-high-resolution, 3D-volume imaging sub-bottom profiling system capable of low-cost, large-scale, deep-water (600m) mapping from a low-specification survey support vessel. Since 2001 De Beers Marine (DBM) has been routinely operating an Autonomous Underwater Vehicle (AUV) as its principle, ultra-high-resolution geosurvey... (read more)
2008-01-01 01:00:00

Slocum Gliders Make Historic Voyages

Autonomous vehicles from the company founded by AUV pioneer Doug Webb have recently made a historic 2600km voyage from New Jersey to Halifax and successfully drawn power from ocean thermal gradients for 3000km worth of data collection between St Thomas and St Croix.<P> Ocean engineers’ dreams docome true, as demonstrated by Doug Webb of Teledyne Webb Research, Falmouth, Massachusetts, USA. When he left the Woods Hole Oceanographic Institution in 1982 after 20 years there, it was to form his own company Webb Research Corporation, recently acquired by Teledyne, to develop and manufacture floats and sound sources. However, he was dreaming... (read more)
2008-08-27 12:00:00

Data Comparison of the SeaBat7125 and 8125 Multi-beam

Survey specifications such as the Land Information New Zealand (LINZ) require a specified number of hits on a given target size and a specified overlap in Special Order areas. In practice, the surveyor has two options to increase the number of hits: reduce the range to increase number of hits or slow down the vessel to increase sounding density. A multi-beam echosounder (MBES) with an equi-distance possibility increases the number of hits at the sides of the swath. This article describes a comparison survey with two SeaBat MBESs: one with equi-angle mode and one operated in equi-distant mode.<P> With beams... (read more)
2008-05-30 12:00:00

Technology in Focus: Multi-beam Echosounders

New Technology, New Capabilities and New Markets
The evolution of multi-beam echo sounders (MBES) is leading to systems with enhanced capabilities in their traditional markets, but also provides features to allow the expansion of their use into new areas and applications. This short review highlights some of the features of the latest generation of systems. The attributes of an MBES system are traditionally described by technical specifications, such as operating frequency, pulse length, beamwidth, number of beams and coverage. These technical parameters define the nature of the system, but the fundamental characteristics of greatest interest. By Dave Mann, Gardline Geosurvey, UK. Just as technological advances mean there... (read more)
2013-03-26 02:25:34

A Flooded Landscape Revealed

3D Hydrodynamic Model Developed for Sustainable Water Abstraction
During the last week of a hydrographic survey of Lough Derg, Ireland’s third largest lake, the remnants of a preserved flooded landscape were unveiled beneath the surface with each passing swath. In early 2015, Geomara was commissioned by the utility company, Irish Water, to undertake a bathymetry and side-scan sonar survey of Lough Derg as part of the planning and design process for the Water Supply Project, Eastern and Midlands Region. This project aims to find a new water source to supply the future needs of the Midlands and Greater Dublin Area.  Over the course of a typically wet and... (read more)
2016-04-04 10:00:41

Qualifying Heave Performance at Sea

Comparison of ORE MEMS-based MRU Heave Measurement with RTK-GPS
When accelerometer-based heave units were developed, there were limited options for verifying their performance at sea with a recognised standard. With real-time kinematic (RTK) global positioning system (GPS) devices, surveyors today can achieve accuracies of 2cm in altitude measurement. With the advent of small, low-cost, low-power, micro-electrical mechanical systems being employed for motion-sensing, a compact and cheaper alternative is available to measure heave. We have verified the heave of our motion reference units at sea with RTK-GPS. View Larger Map ORE Offshoreadded heavemeasurement to their pitch-and-roll motion reference units (MRU) in April 2009, which use micro-electrical mechanical system (MEMS) sensors.... (read more)
2009-06-26 12:00:00

Data Integration for Coastal Surveying

Combining Laser Scanner and Bathymetric Sensor
When surveying the coastline, the integration of bathymetric (below sea level) and laser scanning (above sea level) data causes problems due to the different imaging properties. However, by ensuring that the different data sets have been accurately georeferenced and oriented, a complete and accurate model of the terrain above and below sea level can be obtained. This technique was employed to survey the area of Portovenere in Italy, including the San Pietro church located on a steeply sloping rocky promontory, with positional accuracies in the order of 5cm.<P> View Larger Map One of the biggest issues incoastline survey is the... (read more)
2009-06-04 12:00:00

USGS Tethered ACP Platforms

New design means more safety and accuracy
The US Geological Survey has developed an innovative tethered platform that supports an Acoustic Current Profiler (ACP) in making stream-flow measurements (use of the term ACP in this article refers to a class of instruments and not a specific brand name or model). The tethered platform reduces the hazards involved in conventional methods of stream-flow measurement. The use of the platform reduces or eliminates time spent by personnel in streams and boats or on bridges and cable-way and stream-flow measurement accuracy is increased. One vital mission of the US Geological Survey (USGS) is to provide flow data for streams across... (read more)
2008-01-01 01:00:00

Valeport Sensors Selected for New Micro AUV

Valeport has recently collaborated with ecoSUB who produce a micro AUV that is both advanced and cost-effective. The small and robust sensors are assisting Autonomous Underwater Vehicle (AUV) manufacturers and users to not only get the data they require, but to make AUVs more accessible in the marine environment. ecoSUB is a micro AUV (0.5 metres long) that uses Valeport’s sensors to autonomously acquire sound velocity profiles and has been jointly developed by Planet Ocean and Marine Autonomous Robotics Systems (MARS) group at the National Oceanography Centre (NOC) in Southampton. Part funded by Innovate UK and the UK Defence Science... (read more)
2018-12-17 09:16:40
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