January 2008 Issue
Have GPS, Digital Charts, and Radar Replaced the True Art of Navigation?
Navigating aboard a boat has never been easier, but many GPS-reliant skippers today lack the necessary skills to make it back to port if the GPS signal fails.
Over the last 30 years, nothing in recreational boating has changed as much as the navigatorís routine. In 1975, the practice of fixing oneís position offshore wasnít much different from that used by navigators of 1875. However, by the start of the 21st century, the modern navigator has more in common with Captain Kirk than Captain Cook.
At the heart of the change is the U.S. Defense Departmentís development of the Global Positioning System (GPS), an aid to navigation that has revolutionized missile capability and spun off to become the commercial and recreational sailorís best friend. In all too many cases, however, the GPS receiver is the sole source of navigation information aboard a boat. This satellite-based pied piper steers many contemporary boaters out of sight and into harbors bordered by coral reefs and rocky ledges. Blind allegiance to the system has numbed the navigatorís sense of self-doubt and has sidelined active double-checking procedures such as plotting dead-reckoning (DR) positions, maintaining a deck log, or even the simple act of noting the numbers on the buoys passed.
The system was intended to be used as an aid to navigation, not as a sole source of navigation. The military employs inertial guidance systems and other electronic means of position location to augment and double-check the fixes derived from GPS. Meanwhile, the recreational boating community continues to put all its faith in the reliability of GPS. The question of what happens when the GPS satellites go down was answered a couple of years ago when, for some unknown reason, the GPS signal shut down for boaters in the mid-Atlantic region. Sport fishermen who charge out from New Jersey harbors to deep-water canyons 100 miles or so offshore had satellite guidance on the way out, but the return trip required the use of something other than data displayed on the GPS screen. Having handheld GPS units as navigation backup proved useless. As the boats steered toward home, they wound up scattered along the coast. Many boats ended up closer to Cape Cod (Mass.) and Cape Hatteras (N.C.) than they did to their home ports in New Jersey. Over recent years, traditional DR and piloting skills seem to have suffered. This near-complete reliance upon a single source of navigation information has many experts concerned.
Nothing has exaggerated this concern more than the current emphasis on powerful displays and piling on added graphic features. Digital charts with aerial photos and 3D bottom perspectives are great as long as the blip that represents your boat is accurate. But that is not always the case, as the Queen Elizabeth 2 crew discovered. A few years ago, the ship ran aground after a GPS receiver lost its signal but continued to function in DR mode. Part of the problem is that GPS signals are very weak and require high sensitivity and selectivity in a receiver, which means that impedance changes in a cable or antenna due to moisture and corrosion canít be tolerated. GPS are also vulnerable to other intrusions like weather-related precipitation-static or intentional jamming.
Another step in the wrong direction for navigation is the trend to develop hybrid navigation/entertainment networks that allow satellite TV or videos to be fed onto a chartplotter/radar screen. This kind of dual usage may have wide market appeal, but its impact upon watchkeeping can be catastrophic. One magazine article mentioned how during long, boring night watches, a crew member liked being able to watch reruns of "Sex in the City." A quick look at annual U.S. Coast Guard statistics shows that despite the effectiveness of new electronics, failures in watchkeeping continue to be a big problem. Last fall, the 90-foot sailing yacht Essence was headed down Long Island Sound. It was a clear, calm night, and the vessel was equipped with a top-of-the-line navigation suite. Even though conditions were optimal, the vessel had a head-on collision with a 600-foot ship, sinking the yacht and killing one of the crew. This tragic incident underscores the importance of proactive visual watchkeeping and collision avoidance.
Aboard recreational craft, the watch stander, helmsperson, and the navigator may be one-in-the-same, so having a digital charting system and radar that is easy to operate can prove extremely helpful when navigating. This powerful combination of radar and chartplotter (not necessarily an overlay) enables the watch stander to quickly discern the vesselís position, the coastline profile, and radar contact information. The greatest benefit of such an arrangement is that it allows the watch stander to spend more time with his "eyes out of the boat," visually scanning the waters ahead as well as abaft the beam. The ultimate means of target identification remains visual sighting, and it trumps any of the electronic facsimiles. All too often crews get wrapped up in whatís on a screen, and they fail to keep the cockpit or pilot house dark enough to enhance their night vision. Itís no surprise that some crews have hit the nav markers they had used as a waypoint while developing the route.
Radar, for good reason, is every commercial sailorís best electronic friend, and over the years, yacht-size 2- and 4-kilowatt units have gotten more compact, energy efficient, and easy to operate. However, these units typically have small antennas that donít work as well on an angle of heel. Placing these units on a tilting pedestal platform or other means of keeping them level with the horizon pays off in performance. Also, although automatic tune and gain let you easily switch from one range to the next, careful manual tuning and gain control can improve the picture. Radar can have a hard time discerning a small fishing skiff or sea kayaker, especially in rain. In these cases, the human eye and a quality 7x50 binocular may be the navigatorís best friend.
Aids to human visual acuity have improved, thanks to the need for better battlefield night vision. The current generation of light-gathering night-vision scopes can help a crew avoid crab or lobster pots or find a crew member who has gone over the side. It can also be used to spot lights and unlit marks. Image-stabilizing binoculars that take away the blur induced by the boatís rolling motion offer a distinct advantage in daylight. Meanwhile, forward-looking infrared radiation (FLIR) scanning technology is changing the seascape at night. The technologyís ability to discern small temperature variations is proving quite useful in distinguishing obstacles once the sun goes down. It has also revolutionized search and rescue. A victim who has fallen into cold water presents a stark contrast and is easily seen on a FLIR display.
The Face of Interface
The head-long charge to lash up sensors to everything from the speed, wind, and depth indicators to sensors that measure the engineís coolant temperature or the volume of liquid in a holding tank, is in full swing. With a National Electronic Manufacturerís Association (NEMA) 2000 networkóan offshoot of the Controller Area Network (CAN) used in the automotive industryónavigation data can be shared among an array of integrated circuit-friendly devices. In a nut shell, a vessel can be monitored like a car on a lift or patient in a hospital bed. Huge amounts of data can be handled and displayed on screens connected to the network, but hereís the rub. All too often a boat owner starts to overload the screen(s) in front of them. The paper chart was bigger than the nav-table, now in many cases, the 10-inch LCD screen (measured diagonally) is split in two with radar on one side and a digital chart on the other. Across the lower portion of the full screen are boxes of networked data further informing or distracting the watchkeeper. Whatís worse, the already too-small viewable chart area may be missing an important marker or obstacle, as the userís effort to "declutter" the chart has hidden this vital piece of information.
In Practical Sailorís opinion, radar should be a stand-alone screen, unencumbered by strings of peripheral data stacked across the bottom. In addition to relying on a digital chartplotter, the navigator should keep a chart kit book or large scale paper chart of the area handy for reference, even if he has laid out a track on the plotter and uses the plotter as a primary source of position information.
While the current network system put even more faith in the GPS-based navigation systems, the offshore navigator should not forget that the U.S. Department of Defense has stated emphatically that GPS is not meant to be a stand-alone system.
Fortunately, GPS is not the only show in town in the coastal U.S. This year, aviators and mariners joined together to lobby Congress to extend the shore-based Loran C navigation system. After years of technical research into the vulnerability of GPS signals, it was a line item in the U.S. Department of Homeland Securityís budget that revived Loran C. Not only has Loran C been reauthorized, but itís being upgraded. Those pack rats who stuck their old Northstar, Furuno, Magellan, Micrologic, or other brand unit on a shelf in the basement have a free back-up system.
In many cases, the old Loran C receiver can be interfaced via an NEMA 0183 link to an onboard network. Or it can simply be used as an independent source for position data. SI-TEX and other manufacturers offer Loran C units in their current product line up. This belt-and-suspenders approach may not be necessary for the average day sailor, but cruisers doing extensive coastal passage making, and those doing a lot of overnight and low-visibility sailing may want to consider making use of a proven electronic backup system.
While weíre out on the limb of resurrecting anachronisms, we might as well go all the way and lift the lid on celestial navigation. This art has come back into vogue at the U.S. Naval Academy and remains an important component of the new commercial Standards of Training Certification, and Watchkeeping (STCW) licensing system. These institutions are not doing so to add busy work to their already over-stuffed curriculums. Their feasibility studies show that under certain sets of constraints, the electronic navigation systems may go down and traditional DR, piloting, and celestial-nav skills would prove to be the only way to navigate. Ocean-crossing cruising sailors should not be so certain that with two handheld GPS units and plenty of AA batteries, they are covered.
Weíre no Luddites, but we also recognize that the blind assumption that electronic equipment on a sailboat can always be counted on at sea is a little too optimistic. And whether itís the failure of a fickle charging system, a black-box dilemma, or a lightning strike that causes the digital charts to vanish, the result is all the same: no fix and no chart. This is the main reason that a backup inventory of paper charts needs to be on hand to go along with an alternate approach to position fixing. The standalone handheld GPS will fill the void if the problem is associated with your built-in system or the ships power supply, but if itís a regional or global system problem, the handheld will be just as dormant as the fixed system. And thatís why a navigation contingency plan makes sense aboard any boat that cruises or races further afield.