Artefacts in Multi-beam Echosounder Data

This article is about my thesis project, which I did in collaboration with Auke van der Werf at the Dutch Nautical Academy at Terschelling (the Netherlands). The research for the thesis was done at the Dutch Directorate General for Public Works and Water Management (Rijkswaterstaat). This article presents a subset of the thesis. I would like to share the knowledge I gained and the lessons I learnt about lever-arm errors, motion time delays and yaw misalignment, which can result in dynamic motion residuals, also called artefacts or wobbles.<P>   Over the last decade, Rijkswaterstaat (part of the Dutch Ministry of... (read more)
2008-05-30 12:00:00

CUBE: Extended Applications

Many hydrographers consider the Combined Uncertainty and Bathymetry Estimator (CUBE) algorithm a useful aid in processing bathymetric data and ‘measuring’ survey quality. This paper discusses extending the use of CUBE to include determining multi-beam echo sounder (MBES) offset parameters and navigation offsets between overlapping survey lines. One critical process in MBES surveying is determining system offset parameters by conducting a patch-test. Roll offset is typically recognised by unrealistic bottom slopes. Pitch, time and yaw offsets are recognised by seafloor features appearing dis- placed when surveyed on different lines where survey speed and/or direction vary. Detecting displacements is difficult in shallow... (read more)
2008-01-01 01:00:00

The MRU and SRF Aligned (I)

With increasing accuracies of positioning and multi-beam systems, alignment of the motion reference unit (MRU) is becoming increasingly important. Although most (if not all) multi-beam surveyors use the patch-test to resolve the angular offsets between the multi-beam head and the MRU, this test does not give us the angular offsets between the MRU and the ship’s reference frame (SRF). In addition to this, any misalignment between the vertical rotation axis of the MRU and the SRF (yaw-angle) will introduce cross-talk between pitch and roll.<P> The alignment of the threeaxes is also becoming increasingly important at shallower depths as we should... (read more)
2009-01-05 12:00:00

Kongsberg EM2040 Dual Head on Stril Explorer

A new Kongsberg EM2040D has been installed on MMT’s long-term charted multipurpose support vessel Stril Explorer. The device has a 0.4 x 0.7 degree dual-head multibeam system and it combines all of the features of deepwater echosounders for the shallow-water or ROV/AUV environment. Such features include: Dual swath per ping to maintain a high survey speed at maintained resolution. FM chirp to achieve a much longer range capability Complete roll, pitch and yaw stabilisation Near-field focusing both when transmitting and receiving By owning and operating an EM2040 dual head on Stril Explorer, MMT is further prepared to perform surveys that... (read more)
2014-03-25 12:26:50

GL Certification for Tidal Energy Converter Prototype

Germanischer Lloyd (GL) Renewables Certification (GL RC, Germany) is to certify Kawasaki Heavy Industries' (KHI) tidal energy converter prototype. The certification will be carried out according to GL RC's Guideline for the Certification of Ocean Energy Converters and other relevant GL RC rules and guidelines for marine and offshore structures. KHI's tidal energy converter is currently under development at KHI's Akashi facility and will soon be installed at the European Marine Energy Test Centre (EMEC) in Orkney, Scotland/UK. The prototype certification by GL Renewables Certification will include assessment of the prototype design which demonstrates the fulfilment of the requirements in... (read more)
2012-04-23 10:13:18

Jasco Amar Mission to Venus Ocean Observatory

JASCO Applied Sciences has commenced an AMAR product demonstration and data gathering mission on the Venus Ocean Observatory. Two of JASCO’s AMARs have been deployed at two different locations on the Venus Ocean Observatory in the Strait of Georgia, Canada. The primary purpose is to demonstrate the multi-sensor, real-time data collection and streaming capability of JASCO’s AMAR product. Of specific interest to JASCO are the real-time detection, identification and localisation of individual southern resident killer whales. The AMAR is JASCO’s product offering for the real-time collection and delivery of data and information for ocean observing. AMAR enables scientists to collect... (read more)
2014-03-17 02:29:01

The MRU and SRF Aligned (II and III)

The alignment of the motion reference unit (MRU) is important for the accuracy of a multi-beam survey. The patch test is mostly used to solve angular offsets between the multi-beam head and the MRU; however, this does not solve all the aspects that must be taken into account. This article in two parts describes the method used by the Survey Department of the Directorate-General for Public Works and Water Management (Rijkswaterstaat; The Netherlands), which for reference purposes in this article we shall call the ‘Dutch method’.<P> As explained in Part I in theprevious issue of Hydrointer­national, the alignment of the... (read more)
2009-01-05 12:00:00

Applanix Releases the Latest Version of its DSS Digital Sensor System

Applanix introduced the latest version of its DSS Digital Sensor System. The new system incorporates a next-generation CCD, and single-axis azimuth mount, both designed to maximise the DSS system's capabilities in generating high-quality digital imagery for the aerial survey and remote sensing industry. The DSS is a medium format, digital airborne remote sensing system, using Integrated Inertial technology to produce georeferenced colour and Colour Infrared (CIR) imagery. The system's new super-fast digital chip delivers a 2.5 second cycle time for rapid data capture, together with enhanced pixel dynamics. Additionally, DSS systems now include an azimuth mount designed to remove the... (read more)
2004-06-07 12:00:00

Dual Head Echo Sounder Installation

MMT Group has purchased and installed a Kongsberg EM2040D dual head multi-beam echo sounder on its survey and ROV vessel IceBeam. By operating an EM 2040 dual head, MMT is even-better prepared to perform surveys that meet the IHO-S44 special order.   According to Kongsberg, this is the first multi-beam echo sounder to combine all of the advanced features of deepwater echo sounders to the near-bottom sounding environment. Such features include dual swath per ping to maintain a high survey speed; FM chirp to achieve a much longer range capability; complete roll, pitch and yaw stabilisation and near-field focusing both... (read more)
2011-10-31 11:24:26

Vessel Motion Monitoring Systems for Wind Farms

OSIL, UK, has announced the launch of a Vessel Motion Monitoring System (VMMS), a system designed to monitor motion of a vessel in order to increase safety of transfers during offshore wind farm operations. With a second generation 6 DoF (Degrees of Freedom) motion sensor, the Vessel Motion Monitoring System monitors safety thresholds for heading, heave, pitch, roll, sway and yaw. This portable, battery powered monitoring system has a removable hard disk for data retrieval, and is programmed to display a red signal to indicate when it is unsafe to transfer because safety thresholds have been exceeded. The Vessel Motion... (read more)
2012-11-02 09:25:36
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