Solving the Uncertainty Management Puzzle

Understanding the Limitations of Instrumentation
As shipping companies continue to make their operations more cost efficient and environmentally friendly, the demand for high density data has increased. Uncertainty management is a cornerstone to sound Geomatics practice and it’s the uncertainty values that will drive the next generation high density bathymetry surveys. The main goal of uncertainty management is to allow a survey organisation to accurately determine their adherence to international survey specifications (e.g. IHO S44 5th Edition) and/or to internal specifications. Having realistic estimates for uncertainty, hydrographic surveyors can use this information to adequately design, plan and execute survey methodology and special procedures to ensure... (read more)
2011-07-18 02:30:43

Rheology as a Survey Tool

“We Are Not There Yet”
To reduce the dredging cost many harbour authorities and governmental bodies are seeking for a more suitable and a rheology-related survey tool. The in situ instruments available on the market are based on mechanical, acoustical, optical or radioactive measuring principles. But before one will be able to map the real nautical bottom, we need to understand the influence of the mud properties (micro scale) on a vessel (macro scale). This article gives an overview of the general reaction forces of the mud which definitely play an important role in the vessel behaviour when sailing into it. Without naming any commercial... (read more)
2011-05-17 03:42:46

World's First Fully Autonomous Hydrographic Survey

No Line Plan, No Boat Crew, Just Sensors
During September 2017, the world’s first autonomous hydrographic survey was performed. 'Autonomous' means not by remote control, but rather that the autonomous surface vehicle (ASV) used guidance from survey software to run pre-planned survey lines or automatically generated lines based on sonar coverage, with human interaction possible but not required. The Channel Coastal Observatory (CCO) commissioned 4D Ocean to undertake a hydrographic survey of the seabed offshore of Hurst Spit, Western Solent, using a SeaRobotics ASV 2.5. The pilot survey was supported by the Maritime & Coastguard Agency (MCA) and UK Hydrographic Office (UKHO). By Duncan Mallace, contributing editor, Hydro... (read more)
2018-02-13 11:36:29

Shallow Inland Water Bathymetry Meets IHO S-44 Special Order

Application of the Kongsberg GeoSwath System
For many years, the GeoSwath system from Kongsberg GeoAcoustics has been providing an efficient simultaneous swath bathymetry and sidescan seabed mapping solution with accuracies that meet the IHO S-44 Special Order standard for hydrographic surveys. GeoSwath systems have been fitted to a number of small crafts and have been utilised to conduct bathymetric surveys of lakes, ponds, dams and rivers. This article describes two of the vessels that have been employed to undertake this area of work. The use of Unmanned Surface Vessel (USVs) allows surveying in locations and situations in which deployment of conventional platforms is not practical or... (read more)
2018-02-27 01:01:18

‘Killer’ AUV Sonar System

In January 2001, C&C Technologies (C&C), a company based in Lafayette (Louisiana, USA), introduced the first commercially successful autonomous underwater vehicle (AUV) to the offshore industry. The AUV’s survey sensor suite, which included an EdgeTech side-scan sonar and sub-bottom profiler, performed well in the Gulf of Mexico and Brazilian offshore environments. However, West Africa proved more challenging – particularly for the sub-bottom profiler. C&C soon began searching for alternative technologies to provide better sub-bottom profiler penetration and higher resolution side-scan sonar imaging.Jim Chance, C&C Technologies (USA) Art Kleiner, EdgeTech (USA)<P> Narrator: Fast forward to the early autumn of 2004… C&C... (read more)
2008-04-02 12:00:00

Satellite Positioning

Within the last twenty years Global Positioning System (GPS) receivers have revolutionised navigation. Integrated devices are capable of providing time, position, height, direction, heave and attitude to accuracies of a few nanoseconds time, 1cm position or 0.01 degree heading. All potentially displayed on a digital chart background with radar and auto-identification system overlays. In this first of two articles we look at current Satellite Positioning systems, how they work and how we can make them better. In a second article, to appear next month, we explore the future development of Satellite Positioning and the implications for navigation. How does Satellite... (read more)
2008-01-01 01:00:00

The New IHO S-102 Standard

Charting a New Frontier for Bathymetry
Soundings and contours are the only official way data producers can push bathymetric information to the wide hydrographic community. The introduction of the S-102 standard for bathymetry will enable many possibilities within the community of bathymetry users. Liaising with the International Hydrographic Organization’s (IHO) TSMAD working group, the Canadian Hydrographic Service (CHS) and the US Naval Oceanographic Office (NAVO) led the development and practical testing of this revolutionary standard, officially called the Bathymetric Surface Product Specification S 102. In partnership with IIC Technologies, GeoNet Technologies, and CARIS, CHS created one of the first prototypes of S 102 datasets, using the... (read more)
2012-05-02 04:49:07

Unravelling the Ridge and Rift

Missed Opportunities and Triumph
Following Maurice Ewing’s first cruise to the Mid-Atlantic Ridge, two more were made by the end of the 1940s. The first of these was led by Ewing while the second was led by Bruce Heezen. Although Gunter Dietrich’s paper was referred to in the 1949 paper by Ivan Tolstoy and Ewing (see part I in last issue), neither seems to have comprehended its significance as he reported in the November 1949 National Geographic magazine: “Crossing the ridge, we drew a detailed profile of its peaks with our fathometer. Flanking the central highlands, we found deep trenches separating the main Ridge... (read more)
2014-10-15 02:53:21

Assessing the Quality of Soundings

Ensuring that your hydrographic data complies with the latest standards can be difficult, particularly as standards continually change with new advances in technology. Simon Squibb discusses a ‘binning’ technique that may improve data confidence for surveyors and clients. The standards for hydrographic measurements are regularly reviewed to cope with advances in technology and the demand for higher accuracy data, which continually increases. For example, last year the 4th edition of the international standard, IHO S44 (1), was modified by various hydrographic authorities to meet wider application. To aid their surveyors in assessing the quality of data collected, Andrews Survey has... (read more)
2008-01-01 01:00:00

Synthetic Aperture Sonar Challenges

Synthetic aperture sonar (SAS) has been under active development for decades. The technique is particularly well suited for autonomous underwater vehicles, and it is expected that SAS will replace traditional side-scan sonars for many ‘high-end’ AUV applications in the years to come. Research systems have been used for more than 15 years and many R&D groups around the world have been able to present images that would not have been possible to produce using traditional sonars. However, in many cases, these impressive sonar images are the result of days of tuning and tweaking by experts. A lot of effort has... (read more)
2008-05-15 12:00:00
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