With their ability to get position data from a GPS or DGPS and show a vessel’s location, electronic charts have great value. However, often there are situations when you want to see the relevant chart while in the cockpit and not down at the nav station. For sailboats, the solution to that problem is to put a display unit somewhere out in the cockpit.
There are now a variety of companies offering display screens that can take the VGA or SVGA output from a desktop or laptop PC and display it in the cockpit on a unit designed to live out in the marine environment. In addition, several firms are also selling not just a remote display but a complete computer with its own CPU, RAM, and video circuitry all encased in a relatively thin, waterproof box.
This technology seems to be sparking a convergence of various pieces of marine electronics. At least one company, PinPoint Systems International of Westhampton Beach, N.Y., is selling a PC expansion card that can take the output from a radar and display it on a computer screen. According to some industry observers, this capability is part of a coming trend toward running the output from most, if not all, electronic boxes into a PC for processing and display. In this scenario, there would no longer be separate GPS, radar, electronic chart, and sailing instrument boxes with their own displays. Instead, all these units would gather data and then shoot it down a network bus to the computer where it could be arranged and rearranged and ultimately displayed in any way the user chooses. For example, you could decide to view only your electronic chart, the electronic chart and a radar image side by side, or the chart with the radar image laid over it.
Having a computer screen in the cockpit has always been problematic because of the depth dimension of even the smallest of cathode ray tube (CRT) displays. Most people simply weren’t interested in putting a CRT on their steering pedestalor anywhere else in the cockpit for that matter. The difference is the great strides that have been made in liquid crystal displays (LCD). Driven by the fast-moving laptop computer market, LCD screens have greatly improved in their ability to crisply display color at high resolution. These improved “flat panel” screens take up less space and so can be mounted just about anywhere. Some of the firms offering these displays are: Advanced Engineering & Electronics of Newport, R.I.; Cascade Technology Corp. of Farmington Hills, Mich.; Aqua-Logic Ltd. of Christ-church, Dorset, in the U.K.; and Sports Products Inc. of Lexington, Mass.While older color LCD displays used so-called passive-matrix displays that were slow-er to update and were prone to “smearing” images, most color LCD screens now use active-matrix LCDs. In addition to providing an image that is sharp and redraws crisply, active-matrix color LCDs have a wider viewing angle and can reproduce a greater range of colors. One downside to active-matrix displays is their greater expense, but the price for active-matrix units is dropping as they become the standard for laptops.
One issue that has held back the use of computer displays in the average sailboat cockpit has been the effect of bright sunlight. A standard color LCD display can’t be read when the ambient light is too high. This is because, unlike the glowing phosphors of a CRT, which are refreshed and re-energized by an electron beam, LCD units rely on the polarization of light to display an image. One way to think of light polarization is to imagine photons “spinning” in different directions. By putting an electrical charge into a liquid crystal, the crystal material can be made to block light of a certain polarity (or “spin”), making the pixel look dark. This works perfectly well, as millions of wearers of digital watches will attest. However, unlike the glowing phosphors on a CRT, LCDs don’t produce any light of their ownthey merely affect the light passing through them. Thus, in dark conditions, a color LCD is unreadable unless it is backlit.
Simple, low-cost handheld calculators with LCDs often use a mirror or shiny plastic to ensure that most of the light entering the LCD bounces back out again. For an LCD computer screen some type of light source is required to send enough light through the crystal matrix so that the color image is visible in low light. It turns out that in high light situations, like bright sunlight, backlighting is also required so that the light coming through the matrix isn’t overwhelmed by all the incoherent light bouncing around on a sunny day.
Backlighting is done by placing fluorescent tubes behind the LCD. These tubes are what provide the brightness necessary so that the display can be readable in daylight. And the brighter the screen, the easier it will be to read during the day. Advanced Engineering & Electronics, for example, puts 10 cold cathode fluorescent tubes behind the screens on its R104 and W104 models. The brightness of screens is often measured in candlepower per meter squared. If you are in the market for one of these displays, the best idea, of course, is to test-drive each unit on a boat in bright sun. Since this is usually impractical, the next best approach is to compare the manufacturer’s claims for screen brightness.
A remote computer display screen sounds simple until you want to interact with the computer. Obviously, trying to use a mouse while steering the boat is difficult. Cockpit display manufacturers have addressed this problem in two ways. One is to put buttons on the case of the unit that fulfill the function of a mouse and can control the screen cursor, etc. The other option is to outfit the unit with a touch screen. Touch screens never really caught on with the desktop computer crowd, but for a remote display, a touch screen makes sense. Touch screens do add cost to the unit and may take some getting used to, but they eliminate the need for a pointing device. Advanced Engineering & Electronics, for example, uses a capacitive touch screen instead of a resistive touch screen because AE&E claims that this prevents raindrops from registering on the display.
In addition to remote display units, there are also display panel PCs with their own microprocessor on board. Some of these are only intended for bulkhead mounting, others are designed to sit on a steering pedestal out in the weather. One of the biggest issues for this type of unit isn’t waterproofing but heat. Remote display units have video circuitry in board, and they get warm, but due to the type of chips used and the low chip count, heat dissipation is fairly straightforward. However, a unit with a 486 or Pentium central processing unit (CPU) chip built in has a bigger challenge, since CPU chips produce more heat than do video boards.
Manufacturers like Cascade Technology Corp. claim to have solved these problems. Cascade took its DiscoveryMATE R104 display and added a 133 MHz Pentium CPU board and calls the unit the DiscoveryMATE IPC. Another company offering a display with a built-in CPU is Ocean PC of Seattle, Wash. Ocean PC offers four different units with a mixture of processor options and screen types, all running Windows 95. Also, a company in the U.K., AquaLogic, has a unit called Console PC that uses a 486-level processor.
These new cockpit displays and cockpit computers give the voyager the ability to see navigational information while still at the wheel. In many situations this is great way to keep up to date on the boat’s overall situation. Of course, all this technology hasn’t changed the fact that simply eyeballing one’s position on an electronic chart is not good navigational practice. Logging and plotting a DR that has been updated with electronic, visual, and radar fixes is still the best way to navigate.