dynamic positioning
Vessels working in the vicinity of a platform could be vulnerable to unintentional – and intentional – disruption of GNSS, it is claimed
Seminar highlights GNSS concerns
A
s made plain in a report published last year by the Royal Academy of Engineering in the UK, all types of
global navigation satellite systems (GNSS) are vulnerable to failure, disruption and interference, and much work has been (and is being) done to assess the possible failure modes and their effects on services, and to develop strategies to detect failures and correct them.
Many of the potential problems with GNSS relate to the fact that the signals are very weak – typically less than 100 watts transmitted from a distance of 20,000km to 25,000km. When received at the surface of the earth, the signal strength is low, with a spectrum spread out effectively below the noise floor in receivers. Deliberate or unintentional interference with this signal can thus easily defeat the signal recovery or
A seminar held in the UK highlighted the fact that the GPS signals on which the offshore and other industries increasingly rely, remain vulnerable to intentional and unintentional interference
overload the receiver circuitry. GNSS signals are also vulnerable to disruption in the atmospheric medium through which they pass, and receivers can also unintentionally lock onto reflections of the signals, known as multipath, giving unexpectedly large errors. These causes can have quite different effects on users, such as partial or complete loss of the positioning and timing service, poorer accuracy, very large jumps in position, velocity or time, and
‘hazardously misleading information’ (that is, believable data that is dangerously wrong in safety-critical applications). At the one-day event held at the National Laboratory
Physical outside London a
number of threats to GNSS and to GPS were discussed. Todd Humphreys, director of the radio-navigation laboratory at the University of Texas-Austin delivered the keynote; other speakers included David Last, a consultant to the General Lighthouse Authorities of the UK and Ireland, and Pieter Toor, research and innovation manager at Veripos in the UK. The event was organised by the Position, Navigation and Timing Network, part of the UK’s Knowledge Transfer Networks (KTN), which are designed to stimulate innovation in the economy through higher levels of research and development and knowledge transfer. The event was co-sponsored by the Royal
SeeByte collaboration with SMD bearing fruit
SeeByte and Soil Machine Dynamics Ltd (SMD) say their technology partnership is bearing fruit.
SeeByte and SMD plan to integrate a smart software tool for dynamic positioning and real-time monitoring
www.osjonline.com
of ROVs, based on SeeByte’s CoPilot technology, into SMD’s DVECSII control platform. This will be available on SMD’s latest generation ROV systems, the first of which is the Atom. SeeTrack CoPilot offers an extensive
range of operation modes such as stationkeeping, cruise control, survey control, multibeam imaging, sonar track and mid-water DP. SeeTrack CoPilot for SMD ROVs was due to be available as of May 2012.
Offshore Support Journal I June 2012 I 49
Statoil
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