HPR 408S
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Catalog excerpts

Subsea Long Base Line hydroacoustic positioning reference system Increased accuracy requirements Since the shipboard Super Short Base Line (SSBL) system has its accuracy degree as a result of how accurate it is possible to measure the angles down to the transponder, the position error will increase with the range to the transponder. The Long Base Line (LBL) principle of underwater positioning, using range measurements only, will improve the position accuracy and stability of a subsea ROV / structure relative to a seabed transponder array. How accurately is dependant on some practical and physical factors, but, under normal condi- tions, the position stability of the ROV is within a System description The HPR 408S subsea LBL system uses a special beam-forming ROV transducer with a doughnut shaped beam. This beam design is used to concentrate the sensitivity towards the transponder array, and hence reduce the sensitivity towards ROV and surface vessel generated noise. The HPR 408S system has the 3000-m rated subsea transceiver installed on the ROV together with the transducer. The interface to the sur- face is via an optical or electrical serial line through the umbilical to the onboard HPR operator station. The onboard operator station may be the same as the HiPAP or HPR 410/418 system. This will secure full acoustic synchronisation. The LBL position update rate is typically around 2 seconds. The system is a result of demands in the world market when going into deeper waters, where an accurate ROV and subsea module positioning will be more important, as well as accurate subsea infrastructure ranging using LBL calibration routines. • Hundreds of transponder locations • Real time ray-bending error compensation • Global co-ordinate calibration and positioning (if used with a ship system) • Flexible redundant alternatives • 56 different Transponder Channels • Built-in simulation tool to optimise and adjust the transponder turn-around delays Perfect subsea survey tool With its high accuracy, good repeatability and high reliability, HPR 408S is seen as the multi-purpose hydroacoustic positioning system for ROVs, UUVs, AUVs and other subsea devices.

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"World record" The HPR SSBL and LBL systems can operate with up to 56 transponder channels. They also provide trans- ponder telemetry communication for use with trans- ponder release, sensor readings and Long Base Line The HPR 408S transducers have directive receiving beams. This minimises the influence of noise coming from the ROV's thrusters and propellers, as well as sea surface noise. bending and sound velocity errors The HPR 408S takes input of the local sound velocity profile, calculates, error compensates and displays the effect of the physical phenomenons of sound velocity...

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