News»View all»More Harbour Pilots using PPUs
Posted on 10 April 2010

Weighing in at around 11 to 15 pounds, their portability means they can be carried to various locations on or between vessels, making them ideal for the pilot “lifestyle.” Because pilots often work in adverse weather conditions — and often board vessels in those conditions via precarious ladders — most PPUs are housed in weatherproof cases that can be easily carried, with room for GPS antennas, chargers, connectors and cords. They can be set up within minutes.

They integrate with onboard Automatic Identification Systems (AIS) via a “pilot plug,” WiFi network or even Bluetooth for access to ships’ systems and real-time ID information for other vessels in the area. Often, they also have independent GPS receivers so they don’t have to rely on the ship’s systems.

“The big thing is that each (pilot) group has to develop their set of needs, what is it that they want out of a PPU,” said Capt. Jorge Viso, with the Tampa Bay Pilots. “That drives what it’s going to look like. If your primary function is to develop precise navigation information based on your own position on the vessel, you want something that’s heavy on GPS. If you’re more concerned about the traffic picture, you can be more reliant on AIS.”

Each pilot’s territory poses unique challenges. For example, according to a Canadian study assessing PPU use, Fraser River Pilots in British Columbia face regular, unpredictable river shifts. They need accurate — and frequently updated — sounding data. In Halifax Harbour, Nova Scotia, pilots use precise three-dimensional positioning of two suspension bridges linked to tide- and water-level gauges to predict air drafts under the bridges.

To meet such diverse needs, PPUs can be configured to different degrees of accuracy using Differential GPS (DGPS) and Real-Time Kinematic (RTK) systems, which also affect cost.

DGPS applies a secondary source of correction data to raw GPS signals. Accurate to about 24 inches, it can determine speed within two inches per second, and rate of turn within about one degree per minute. The most flexible option, they’re fairly accurate even where secondary correction isn’t available, and can cost around $30,000.

Berthing pilots need the more accurate location and motion data RTK offers. It relies on a base station with known, surveyed coordinates, which it compares against GPS signals for a location accurate to less than an inch under ideal conditions, and speed accurate to within less than a half-inch per second. These PPUs are more expensive than DGPS, ranging from $60,000 (including one RTK base station) to more than $80,000.

Because of their limited range, RTK stations aren’t practical in some areas, including Chesapeake Bay, said Capt. Beth Christman, a pilot who’s on the board of supervisors for the Association of Maryland Pilots. “It’s 200 nautical miles or so,” she said. “To have a system set up there would really take something. RTK is not as critical if you’re not using them for docking. We just need a basic display that tells us our cross-track — we need to know how many feet off centerline we are when we’re transiting our channels, especially in bad visibility.”

Her association has been using PPUs since 1994, and is currently evaluating replacement systems. “We’re going to sit down and decide what we want to do,” she said. “Pilots always like the lightest, but we want accurate, too. You’re always trying to find that compromise.”

Viso said Tampa’s pilots have been using PPUs since 1998, and switched to their current units in 2004. “We use a DGPS antenna, a WiFi connection from an antenna unit to the laptop, and a WiFi to the AIS pilot plug on the ship. Our primary goal was precise positioning in the channel, and secondary was vessel traffic,” he said.

Several manufacturers offer PPUs, including Raven, Arinc, Navicom and Marimatech. The piloting software is proprietary, and most systems can record navigation data for playback, either for training purposes or, in some cases, for liability issues. Higher-end units can predict a vessel’s path based on a pilot-specified heading and intervals. For example, it can forecast where the vessel will be in one, two and three minutes — something Viso said pilots traditionally have done “with fingers and toes.”

Both Christman and Viso said the systems enhance their abilities, but don’t replace their training or experience. “The number one thing a pilot does is look out the window,” Christman said.

Viso agreed. “A PPU is just something else the pilot has at his disposal to do his job,” he said. “They’re highly customized to specific ports, and they’re not appropriate to all places. It’s just a tool. Nobody’s driving with a laptop.”