The Skandi Neptune

People have been commenting on my posts that they don't believe the Skandi ROVs have accurate enough position-detecting capability for my theories to be true. Anonymous people have asked how the subs could possibly find precise underwater locations when GPS signals from satellites cannot possibly penetrate to that depth. I have no idea how far down GPS signals can reach, but the fact is that the ROVs do not attempt to use GPS themselves. Another user named "freethinker" sent in this comment to help explain:

You're right bankster
A quick search on Skandia Neptune reveals -

DYNAMIC POSITIONING
Equipped according to DNV AUTR (NMD Class II) DP requirements.
Type: Kongsberg SDP 21
References: 2 x DGPS, Tautwire, HiPAP 500, HPR

HiPAP and HPR are underwater acoustic nav systems that provide the position of the rov integrated with the GPS position of the support vessel.

And from this web site, that evidently of a photographer of all people, is more technical information on Skandi Neptune:

The Skandi Neptune was built in 2001 as a cable lay vessel and converted to a multi-purpose offshore support vessel in 2005. The vessel is currently on long term charter to Subsea 7. The vessel has been designed and constructed to a very high standard and has the ability to perform a variety of offshore and subsea operations. The following systems provide the vessel with the ability to perform multi-purpose roles, including ROV support, flexible pipelay installations and offshore construction projects. • Two stern mounted main azimuth thrusters combined with a retractable forward azimuth thruster and two bow tunnel thrusters provide excellent manoeuvring capabilities. • A Class 2 (DYNPOS AUTR) Kongsberg Simrad SDP 22 DP System with DGPS, tautwire, HiPAP and HPR reference systems provides a high degree of position keeping accuracy. • An active heave compensated 140 tonne SWL deck crane provides high capacity offshore construction capabilities with the ability to perform ship to ship transfers. • An ROV spread comprising of two permanent side launched 3000m rated workclass ROVs with a full suite of support facilities. • A 7.2 m x 7.2 m moonpool, 130 tonne traction winch and stern sheave arrangement is provided specifically for the installation of flexible pipe and cable from deck mounted portable lay spread systems. • High specification accommodation for 106 persons consisting of single and double berth cabins. A range of office suites and conference facilities are available for project purposes. • A worldwide communication system including KU Band, Inmarsat B and Inmarsat C. The KU Band system can be modified for C Band operations, dependent on area of operation. • An offshore helideck rated for Super Puma L2 operations complete with helideck monitoring system. • A 60 tonne SWL stern mounted A-Frame.

So it appears that the ship is quite modern, well-equipped and capable. The answer to the navigation debate is this: the Skandi system uses a combination of GPS from the ship's onboard receivers along with an acoustically-based navigational system in the ROVs. The mothership's and the subs' computers are in constant communication, combining the data from each to achieve very precise underwater coordinate readings.

There have been two Anonymouses who have mentioned a Youtube video showing the coordinates jumping around wildly onscreen while the ROVs remain still. First, I believe that video to have been doctored, but that doesn't matter. Because I have watched hours of ROV footage, mostly from the twin Skandi submersibles, and I have never seen such "jumping" coordinates. I believe that if that one Youtube video was accurate, it was a point error in the system due to some underwater interference. If anyone has additional evidence that the nav system is inaccurate or unreliable, post it in the comments section.

I'll leave the doubters with this to ponder -- the underwater portion of the overall navigation package keys off of acoustics. If the ROV's coordinates are untrustworthy as you claim, based on a lone Youtube video, why then are there thousands of clips online where the subs are sitting right next to the oil and methane gushers, which necessarily threw off large amounts of acoustic noise, and still show rock-solid coordinates on the screen? The answer is because the system was designed precisely for missions like these, and scientists and engineers are smarter than I am and probably you as well, the one that built these craft, anyway.

The system is accurate. If my detractors have no better argument to dispel my theory than their own speculation that the navigation systems that Skandi employ are unreliable, I think the debate will soon be over. But keep the comments coming. I love a challenge.



UPDATE:

I usually trust Wikipedia no farther than I could throw one of their giant server farms, but on issues of technology and mechanics I've found its information to be reliable. You can read about the enhanced GPS system onboard Skandi Neptune, called DGPS, Differential GPS, here. This appears to be how the rovers get their ultra-accurate undersea coordinates -- their onboard acoustic navigation talks to the ship's main nav computer, which is simultaneously receiving an accurized location signal from it DGPS receiver. I think I have dispelled the rumors by the Anonymouses that there is no way the ROVs know exactly where they are.