The Ranger 2 Pro DP-INS system is being used to support touchdown monitoring surveys of submarine cables, umbilicals, and pipelines and as an independent position reference for the LV 108’s Kongsberg dynamic positioning (DP) system.
The equipment supplied included Sonardyne’s INS sensor co-located with the company’s sixth generation HPT acoustic transceiver. This hardware was installed on one of the vessel’s two Kongsberg through-hull deployment machines and interfaced directly with the vessel’s DP system.
McDermott’s LV 108 entered service in 2015 and is currently on contract in the Ichthys field offshore Western Australia. Designed as a fast-transit, DP-2 vessel for subsea construction support for various water depths, the LV 108 has 21,528 sq ft (2,000 sq m) of deck space and can accommodate a crew of 129.
DP construction and installation vessels such as the LV 108 conventionally rely on ultra-short baseline (USBL) acoustics and the global navigation satellite system (GNSS) as their primary sources of position reference data. However, a vessel’s station-keeping capability can be compromised in the event the USBL is affected by thruster aeration and noise and the GNSS signal is simultaneously interrupted. The latter is particularly common around equatorial regions and during periods of high solar radiation.
Sonardyne says its Ranger 2 Pro DP-INS system addresses this operational vulnerability. It aids vessel positioning by exploiting the long-term accuracy of the company’s Wideband 2 acoustic signal technology with high-integrity, high-update rate inertial measurements. The resulting navigation output has the ability to ride-through short-term acoustic disruptions and is completely independent from GNSS.
Ralph Gall, technical sales manager at Sonardyne, said: “DP-INS is a mature, field proven technology that addresses industry’s need for a third, independent DP reference.”