Introduction
Around the world we are seeing dramatic increases in demands on shipping. Ships are getting bigger, and although new ports are being built to cope with them, many existing ports have little scope to expand. This means:
• Tighter manoeuvring margins;
• Increased stress and demand on the bridge-team;
• Increased stress on pilots; and
• Greater scope for error.
Although historically pilots have relied almost exclusively on their own knowledge, experience and intuition, advances in technology are now available to assist them. Adoption of technology is generally very slow, often because ports have difficulty seeing the benefits that technology can bring. The benefits can vary from port to port, but one example is of a port in Australia which, in one use of their equipment, saved its purchase price several times over – simply by being able to sail a ship which would otherwise have blocked berth until the next tide. This article will explain some of the technological options, and show the level to which each can assist pilots and ports in improving safety and profitability.
Simple (position only) systems
The simplest electronic aid is one that uses a single GPS receiver. The system typically comprises a PDA or laptop and a single antenna, either integrated into the display (typically a PDA), or separate from it with a cable or wireless connection to a laptop display. The latter allows operation inside the wheelhouse and enables more sophisticated software to be used. Navicom Dynamics’ ‘FairwayPilot’ system is an example of this type of system using a wireless data link to a laptop display.
Simple systems are inexpensive and very portable – and may be all that is required in relatively straight and wide channels. For example they show the position of the vessel (or normally its bridge wing, where the antenna is sited) in relation to its surroundings, which can help prevent confusion as to which buoy the ship is passing.
As ships move into more restricted waters, these systems become less effective. The size of the ship in relation to the navigable water becomes significant, and it is critical that the ship’s outline is accurately displayed on the chart. While this can be achieved in some software by entering the ship’s dimensions, together with the offsets of the GPS antenna, the displayed picture is only meaningful if heading is accurate. Simple systems can only assume that ship’s head is the same as the course over ground (COG); while this is a valid assumption when the ship is moving in a straight line with no wind or tidal stream, heading will be gravely in error once the ship starts to turn. At slow speeds, and particularly when using tugs or moving astern, ship’s head and COG may be up to 180º apart.
Advanced (position and heading) systems
For precise navigation in confined waters it is vital to know heading, as this allows every part of the ship to be shown in its correct position on the chart. There are two main ways of obtaining heading and ROT for use on a portable system: AIS, and Portable Pilot Units with their own heading sensors.
Automatic Information Systems (AIS)
In 2004, the IMO made it a mandatory requirement for vessels to have AIS fitted. AIS was primarily developed to provide reliable information about other ships in the vicinity for collision avoidance purposes, but many people have advocated using it as a low-cost solution for supplying ‘own-ship’ navigation information via the Pilot Plug.
Unfortunately, reality falls short of theory, largely because of poor quality source data for the AIS (including gyro errors, lack of ROT data, and imprecise GPS positions), and inadequate physical installation of the systems aboard many ships. Problems with the ‘mandatory’ pilot plug include vessels which are not fitted, difficulty in locating it, and inability to get a data stream due to incorrect wiring. All too often, even when a connection is successful, the high quality data required for close-in pilotage work is simply not available. Distractions while finding and making the connection, combined with unreliable data, do not contribute greatly to vessel safety in pilotage waters.
The result is that in its current state of development, although AIS is very useful for providing information on other ships in the vicinity – particularly if it is displayed on the radar or ENC – the pilot is unlikely to be able to rely on the navigation data provided from the AIS plug for safe, accurate own-ship pilotage. The Nautical Institute has a forum on AIS which provides some interesting insights into these sorts of problems.
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