Hull Inspections of USNS Mercy

On April 23 2004, LinkQuest, worked with Deep Ocean Engineering of San Leandro, California, to demonstrate LinkQuest's PinPoint 1500 acoustic positioning system to US Navy at the US Naval Station, San Diego, California. A Phantom HD2 ROV, installed with the PinPoint transceiver, was used to inspect the USNS Mercy hospital ship docked in the Naval Station. Two PinPoint transponders hanging from concrete docks at the pier were used as positioning base stations. 

USNS Mercy is a 69,000 ton oil tanker converted US Navy hospital ship. The length of the ship is 894 feet. This ship was docked at naval pier 1. The port of the ship was about 2.5 meters from the dock. The bow of the ship was about 15 to 20 meters from the dock. The starboard of the port was about 150 meters from the dock. The water depth was about 5 to 8 meters in the harbor during the demonstration.

The PinPoint positioning system was used to guide the ROV to inspect the port of the ship at fixed depth. A Naval EOD support boat circled around 30 to 50 meters from the bow and starboard of the ship to test the performance of the PinPoint under severe ship noise condition. The PinPoint system provided highly robust and accurate positioning of the ROV under these conditions. The repeatability of the positioning system was also validated by piloting the ROV and revisiting points marked by X, Y, Z values on the plot in the positioning software. The ROV returned to the same physical location repeatedly without error.

The ROV was also used to inspect the bottom of the USNS Mercy where the ship bottom was about 2 meters above the sea bed. The PinPoint system provided excellent position fix.

As a final test of the extraordinary robustness of the PinPoint system, the PinPoint system is used to track the Phantom ROV 2 meters underwater at the ship's port where the gap between the ship's hull and the concrete dock is merely 2.5 meters. There were also a few large floats in the gap. The PinPoint system tracked the ROV reliably during the inspection demo at the port.