NEWS REPRINT
a reprint from DockWalk News, September 2001
Who’s Watching Your Position?
by Larry Spisak
Electronics have made a big difference in the way we use our boats. In the very earliest of times, ships hugged the shore, fearful to venture out of the sight of land. As our knowledge progressed, so did our desire to explore new horizons.
With the advent of Loran (Long Range Radio Navigation) precise position location became the norm. Refinements is the system and demand from both the military and civilian sectors pushed the technology forward. It soon became available to almost any size yacht.
With the launch and implementation of the ring of twenty four satellites that currently make up our navigational system known as GPS (Global Positioning System) it's now quite common to hear skippers talking about four meter accuracy, when less than fifteen years ago, quarter mile accuracy was considered to be cutting edge.
While everyone has pretty much settled in with the latest technology, designers have not been resting on their laurels. Finding new and innovative technology has become the new holy grail for many electronics firms.
The technology was originally designed for the Department of Defense to track trucks and vehicles that transported sensitive materials around the United States. The trucking industry was one of the earliest civilian entities to make use of the various technologies built into the existing, but underutilized GPS system. The need to know where their trucks at all times, both from a safety standpoint and from an economical one led the trucking industry to be early adopters of the technology. Being able to reroute trucks due to weather or scheduling changes has saved the trucking industry millions of dollars.
OnStar (R), used in many GM products, is an off shoot of this technology. It combines the GPS system and the ubiquitous cell phone into a system that can help a stranded motorists almost no matter where they are. Of course where cell phone service is nonexistent, the service is not available.
This technology is slowly becoming available to yachts in a slightly modified form. With the right equipment, yacht owners, captains, and engineers can receive on their hand held devices or over the internet, a virtual check list of their boats systems.
While not yet wide spread, the technology is out there and is simultaneously being developed by several companies. These new devices use proven technology that you can use to receive messages from your boat about the status of your shore power, whether the bilge pumps are running, or when a change is detected in any other monitored system.
The technology will also track your boat, letting you see her position using charts available in most navigational software packages. From the comfort of you home, office, or anywhere you have an internet connection, you can precisely locate your vessel and display it on a chart showing exactly where she is in real time. And you can receive reports, review logs of events and to some extent control certain systems on your boat. This is a great boon for charter companies that would like to know if their boats are operating in the prescribed areas or if they have slipped beyond the boundaries to which they were assigned.
Complimenting the GPS tracking system are nine satellites operated by the now privatized Inmarsat organization, forming the cornerstone of all long-range maritime communications. The system was established under the auspices of the IMO (International Maritime Organization) to provide the industry with a dependable means of emergency communications. It has since evolved to offer a range of voice, fax, telex and data services, according to the service chosen.
Inmarsat D+ is a relatively new technology. It was designed for short messages. This ties in perfectly for operations involving sending GPS data and receiving commands, as they do not require high data throughput. A D+ terminal can transmit two types of messages and an acknowledgment. Short bursts consisting of 64 bits of data including 27 bits of user data or long bursts consisting of 128 bits of data including 64 bits of user data. These messages are transmitted at a bit rate between 4 to 128 bps.
The transmissions take place randomly in time slots similar to other Time Domain Multiple Access (TDMA) techniques.
Each unit first monitors the satellite to determine which time slot it can use. These frames occur every two or four minutes depending on which frame structure (traffic channel subscription) the device is using. Thus, a D+ unit programmed for two -minute frames can only transmit every two minutes. There is a similar structure for transmissions from the Land Earth Station (LES) to the unit. The frame structure and the maximum message lengths are the main limitations to D+ devices. These are not significant limitations in many cases, thus D+ devices are attractive for many applications. The interval between updates on your screen can be changed from within the software. Inmarsat operates a constellation of satellites in geostationary orbit. They cover the world in four regions: Atlantic Ocean Region - East (AOR-E), Atlantic Ocean Region - West (AOR-W), Indian Ocean Region (IOR), and the Pacific Ocean Region (POR). D+ is one of several services available over the Inmarsat constellation. It is a two -way, low data rate service. It was originally designed with global paging and messaging services in mind and thus has higher signal levels to provide some level of building penetration. When applied to a tracking device, this allows for a smaller receive antenna aperture while maintaining high reliability for receiving commands under conditions that may not be possible with other satellite -based systems. D+ has been known to work in some instances where direct line -of-sight is not available.
Most units provide a GPS antenna, a cell phone antenna and an Inmarsat D+ antenna. The GPS antenna is for locating the position of your boat, just as any other GPS antenna would do. The cell phone antenna will keep you in touch for a range of about 15 to 20 miles in most coastal areas. The Inmarsat D+ antenna comes online when the unit senses when it is out of cellular range. This gives you the ability to track your vessel anywhere in the world. All the antennas are small, taking up very little room.
If you leave your boat unattended for long periods of time, it may become the target of thieves. If you noticed that your boat was away from the dock and no one was given permission to move her, you could shut down the engines right from your computer, thus making it easier for law enforcement officials to arrive at the scene and rescue your property, and possibly prevent her from being scuttled.
The cell phone portion works on a technology called CDPD (Cellular Digital Packet Data.) The information about your boat is broken into packets (small clusters of information), and sent along idle channels of existing cellular voice networks. AT&T has fairly extensive coverage of the coastal areas of the United States and other areas are added continuously.
Once your vessel moves out of the normal cell phone operating range, the unit automatically switches to Inmarsat D+ and transmits the signal to a satellite which then relays it to a ground station. The information is then routed over the Internet right to your computer.
One company, Satellite Security Corporation, based in Ft. Lauderdale, has a working unit on the market. The unit can monitor only three shipboard systems, but there are plans to expand the functionality. Graphic representations of various events such as battery voltage, pump cycles and air conditioning temperatures are options that are in the works right now.
If you have to spend time away from your boat, the Locator can reduce the anxiety of leaving her for extended periods of time. You can save a lot of hours of driving time and numerous phone calls to have someone take a look at her, “Just to see if she's all right.” You may even qualify for a reduction in your insurance premiums.
We love our boats and take pride in them. These units give you the ability to look in on her, even if you're far from her berth. That should make both of you feel better.
For more information, contact:
Satellite Security Corporation
1900 SE 15th Street
Fort Lauderdale, FL 33316
(954) 931-3222
kdrum@theboatstation.com
Close Window