For centuries, navigators have relied on paper charts - when they existed - to guide their vessels safely away from shoals and shore, through channels, and into ports. That is changing. While a relatively small number of boats are already using electronic charts, researchers in Nova Scotia and elsewhere are working on even more complex navigational systems using electronic charts.
In the future, ``There may be no paper charts on the bridge,'' says Stephen T. Grant, a project manager at the Bedford Institute of Oceanography here. Today, however, it would be illegal for a captain not to have paper charts available even if the boat has an electronic system.
A major test of several electronic chart systems that present charts on a video display, such as that used in computers, began last month in the North Sea region.
It could be five to 10 years before a ``full blown'' electronic chart system has been developed, Mr. Grant figures. It could take another five to 10 years for governments to have sufficient faith in electronic charts to give them the same legal status as paper charts have now. Should a ship meet disaster because its navigator relied on a mistaken chart, the owner of the vessel can sue the government for damages. The legal status of electronic charts is unclear.
At the moment, most mariners locate their vessel's position at sea by monitoring compass, Loran-C (long-range navigation using radar) numbers, navigation charts, depth sounder, radar pictures, and their view from the wheelhouse.
A full-fledged electronic chart system could dramatically improve the safety of navigation by giving the mariner a continuously updated bird's-eye view, on a video screen, of his own ship in relation to other ships, the shoals, and safe channels.
Combined with tide tables, the electronic chart could show the mariner whether a channel is safe at that specific moment for the depth his boat draws. The size of the channel on the screen would grow or shrink as the tide rose or fell. In a harbor, the screen could show the wakes of other vessels as they moved about.
The system could help large tankers berth safely in congested harbors and enable ferries to run on schedule despite fog or wind-driven snow. Ultimately, it could reduce shipping costs. Fewer grounded ships, fewer lives lost, and reduced oil spills and lost property could trim insurance premiums. It should also simplify navigation for the growing number of pleasure boaters, some of whom have limited navigational skills.
Mr. Grant sees the Electronic Chart Display and Information System (ECDIS), as it is called, playing a special role in the Arctic Ocean. This is because the mariner will be able to superimpose the radar image of the ice edge with the chart background on his screen. The navigator can then see where ice is blocking a navigation channel and figure out where the ice is grounded, something that can be difficult along low-lying coasts.
Three major developments are required before a supersophisticated ECDIS is commercially available, Grant says.
1.Traditional nautical charts must be converted to a digital data base - computerized, if you like. In Canada, only 10 percent of the Canadian Hydrographic Service charts have been produced in a full color digitized version. All the data necessary to make a chart, including water depths, geographic positions, sources of data, and shore positions, are entered into a computer.
At the present rate of conversion, it will be another 20 or 30 years before all of Canada's more than 1,000 nautical charts are digitized. But Grant figures this task could be accomplished faster as the need becomes more evident.
2.The new US satellite navigation setup, Global Positioning System (GPS), must be completed. The last of the necessary 18 satellites is supposed to be launched in the early 1990s. The success of last month's Discovery shuttle mission makes this more likely.
At the moment, GPS signals are available in parts of the world for about 12 hours a day.
GPS lets a mariner position his vessel accurately up to possibly 10 meters (11 yards) - unless the United States decides purposely to degrade the signal to 100 meters or more because of military considerations. In fact, GPS accuracy may well be much greater than chart accuracy in parts of the world like the Arctic.
3.The capability of computer and video hardware must be improved.
The Bedford Institute has an ``electronic chart test bed'' for checking the practicality of various electronic charts being developed. Grant has found that the electronic chart must not be too cluttered with information. The mariner could have the option of including in his chart just the information he needs at that moment for safe navigation.
One other advantage of the electronic chart is that it could be updated electronically rather than by printed mariners' bulletins when a light is out of order or a buoy moved by ice or storm.
About eight companies have already come up with commercial variations of electronic charts in the US, and several others in Europe or Japan.
In one such system, Laser Plot Inc., of Auburn, Mass., has electronically scanned paper charts and digitized that information on compact discs. The mariner has a laser reader similar to that used in compact disc players. Instead of getting sound, however, the machine produces an image on a screen. Laser Plot has sold about 100 of the $11,000-plus systems to fishermen and recreational boaters.
Another system, made by Fair Tide Technologies Inc., Burlington, Mass., employs standard personal computers made by International Business Machines or Apple. Fair Tide has redrawn the nautical charts, somewhat simplified, into a floppy disk program. For prices ranging from $395 to $895, it also uses information from the various navigational aids to portray a small boat on the screen. The boater can update the electronic chart himself.