What’s Down Below??

Why ROTVs are Useful Tools in Answering This Question

Early in the first quarter of 2007, Noordhoek Survey took delivery of two MacArtney Focus-2 Remotely Operated Towed Vehicles (ROTVs). The expectation was that the new ROTVs would be a valuable addition to the existing fleet of underwater vehicles. Now, half a year and hundreds of survey kilometres later, these expectations have proven to be correct.<P> Over the past 15 years, Noordhoek has gained valuable experience in ROV and towfish surveys. The new Focus-2 ROTVs fill the gap that used to exist between the specific competences of these two survey platforms. The ROTV body (1.25x1.25x1.85m) consists of four carbon-fibre hulls,... (read more)

2007-11-27 12:00:00

Quality Control of Survey Data

A Continuous Process?

Quality control of survey data is an integral part of any hydrographic survey or inspection operation, but the focus is too often concentrated on the wrong sensors, the carrying out of unnecessary comparisons and ultimately burying real issues in a flood of confusing and contradictory error messages, print-outs and alarms. So what is meant by quality control of survey data, why do we need it, how should we measure it and when is the best time to carry it out? ‘Quality’ is a phrase often used and is expected to be highly visible in the literature and mission statements of... (read more)

2013-09-06 04:37:34

Hydrographic Use of Satellite Imagery in South Pacific

The French Hydrographic Office (SHOM) uses remotely sensed visible imagery for the cartography of atolls and reefs. It is considered as an efficient and relatively inexpensive method to collect information where data is sparse. Remotely sensed visible imagery is used in Pacific French Overseas territories for the cartography of atolls, reefs et cetera. All shallow-water areas may be involved, in particular when the cost of usual hydrography would be out of proportion with maritime traffic. Remotely sensed imagery is mixed with all field information available (bathymetry, buoys, seamarks) and a ‘spatiocarte’ (spatio-chart) is produced, which provides information on: Land: coastline,... (read more)

2008-01-01 01:00:00

Successful Delivery of Coastal Survey Data to the Royal Australian Navy

IHO Order 1b Bathymetric Lidar Data

Amongst the largest contracted coastal hydrographic Lidar survey projects awarded in recent years is the Australian Hydrographic Service (AHS) survey of the Torres Strait in Northern Queensland. The intent of this very large survey was to update nautical charting in the region, facilitate safer navigation and enhance the capacity of maritime enforcement vessels to protect and secure Australian waters from incursions by illegal foreign fishing vessels. As it was to be used for international chart products, the survey data had to be of an accordingly high standard. Approximately 850km north from Cairns, the Torres Strait forms the confluence between the... (read more)

2010-05-31 10:44:08

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

Magnetometry in Wreck Removal Western Scheldt

The Western Scheldt is being deepened to give larger ships better access to the port of Antwerp. Over fifty wrecks and other obstacles have been removed from the main channel. Magnetometry was one of several surveying techniques deployed to determine the exact position and depth of the wrecks to be removed and as a final check after the wreck removal operation. In order to get the best positioning results an algorithm was developed to invert the magnetometry measurements. The Western Scheldt is the gateway to Antwerp and one of the busiest shipping estuaries in the world. It is essential that... (read more)

2008-01-01 01:00:00

Relationship between Gas-bearing Sediments and Biogenic Mounds

Student Research Project in Hydrography

Here we present the winning project of an industry-supported student research campaign, initiated in 2013 by Innomar Technologie GmbH, Germany. More than 25 European scientific institutions participated with research proposals from Master and PhD students in order to perform a hydrographic and geophysical survey with a combined parametric sub-bottom profiler and side-scan sonar system. Complete survey equipment and on-site training was granted to the University of Wien, Austria, the University of Oxford, UK and the University of the Aegean, Greece. The Kalloni Gulf is a large (20km long) and shallow (<20m deep) semi-enclosed embayment, on the western side of Lesvos... (read more)

2014-12-15 01:51:21

Amplified Sediment Waves in the Irish Sea (AmSedIS)

Understanding Big Sand Wave Behaviour

Large sediment waves are striking yet poorly understood seabed features in many shelf seas. Very large sediment waves (3–18m in height) have been documented to migrate up to 70m per year in the Irish Sea and some sand waves reach heights of up to 36m (Figure 1). Such transport of enormous sediment volumes can endanger the stability of submarine pylons, cables and pipes and they cause a highly mobile benthic habitat. To understand the dynamics of these sediment waves, we identified that we need to focus our investigation on the effects of sediment grain size variability, the availability of mobile... (read more)

2014-04-07 01:31:38

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

Improving the Accuracy of ADCP Discharge Measurements

Automating Edge Discharge Calculation in ADCP Software

There is a key new feature in the discharge measurement software ViSea DAS that allows the user to add a bottom profile. By doing so, side extrapolation from the start and end points of the survey track to the shore is calculated automatically using dGPS positioning. This removes the error inherent in estimating the track to shore distance for each individual track, which is the current method used in comparable software packages. This paper describes research that validates this new approach. Discharge measurements are important for the characterisation of rivers and are the basis of many models. There are many... (read more)

2014-05-19 02:19:44