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Simrad HiPAP/ Sonardyne L/USBL systems Comparison - Sea Trials

HiPAP is provided by Kongsberg Simrad as primary and secondary L/USBL Reference of its DP systems.
As no Hipap track record was available for 2300M WD, it was necessary to evaluate the risk associated to the use of Hipap only
for Canyon Express operations.
Extensive sea trials performed in GOM  have shown that HiPAP system performances in deep waters have to be called in question:.

- During Canyon Express pre-survey, HOS INNOVATOR vessel was equipped with both HiPAP and Sonardyne "big head" systems. It was then decided  to carry out  a comparative  study in  deepwater section of the survey area.
-In addition, the impact of replacement of  one DP3's HiPAP by L/USBL Big Head system was studied.

Results of this trials are as follows:

- Quality of positioning using HiPAP in responder (212db) mode and Sonardyne in transponder mode (203 db)  are very similar with fair sea and low noise conditions.
- HiPAP was proven not operational in some occasions (WD 1260m, 1600m, 2200m), when Sonardyne remains fully operational:

• . Presence of higher thruster noise/wash,
• . Occurance of seastate 5
• . presence of acoustic noise from a drilling rig in LBL mode

Conclusion
Most of the time, in fair sea conditions, HiPAP was found operational in the range of waterdepth of the 1500/2300 MSW .
In degraded situations, in noisy environmental conditions and when sea state is high, it was not the case.
Advanced Subsea's advise to project was that with regard to serious doubts about the fact  HiPAP to be able to monitor properly TDP  ROV position in USBL mode, It was mandatory to consider alternate solution as contingency solution.

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