In 1997 GPS (Global Positioning System) sales will continue to grow, yet Loran (Long Range Navigation) will still appeal to certain boaters. Over the past year, GPS prices have fallen dramatically. So have Loran prices. Both systems give most of the same reliable information to the navigator: speed, course, and location - but with differences in accuracy. To better understand these differences, you must understand how each system operates.

Loran is a land-based system of low frequency radio signals transmitted from a master station transmitter and two secondary transmitters. The Loran receiver takes the signals it receives from the master and secondaries, and calculates the position by measuring the time difference (the TDs) between the signals as they arrive.

The Loran system is operated by the Department of Transportation (DOT) and has many advantages. The most important of all its traits is that it more consistent than GPS. This feature is most often appreciated by fishermen and divers where accuracy in returning to a specific location - be it a wreck, reef, or dropoff - is vital. You can return to within 50-75' of the same spot with a Loran. GPS, on the other hand, will be a little different each time you return. Although it is unclear how long after the year 2000 Loran will be funded, substantial lobbying efforts by the marine and aviation industries are underway to keep the system operational indefinitely as a complement to GPS.

GPS is a space-based system which uses signals transmitted from three or more satellites orbiting the earth. As a result, GPS is not susceptible to outside interference (unlike the Loran) such as alternator noise, electrical storms, overhead rigging, TV, or fluorescent lights. With GPS, you have a direct path to the satellites.

GPS has better absolute accuracy if you are getting to a position for the first time. Part of its inability to return to the exact spot can be attributed to "Selective Availability," the error that has been intentionally introduced into the system by the military to protect the U.S. from use of the system by unfriendly forces. "Selective Availability" inserts a random error into the satellite signal, which can affect your GPS position by up to 300' when returning to a location.

When you look at GPS displays, you find the familiar latitude and longitude found on Loran displays. Loran uses TDs and converts that information to latitude and longitude. Some boaters, however, find it easier to use TDs because of the TD lines on their charts. As a result, several manufacturers of GPS now offer products that convert Lat/Lon into TDs. This is where the GPS system really shines. With GPS, you are working in real time, so as your boat increases or decreases in speed, the unit reacts immediately, unlike the Loran which has about a two-minute lag time.

GPS also gives you several choices in equipment: Handhelds, fixed mounts, and accessories to improve accuracy such as differential boxes. Handhelds remain the most popular, even with limitations of battery life, display size, and antenna configuration. The portable antenna on handhelds does not work below deck in all boats and must be in the clear. Most manufacturers offer 12-volt options as well as external antennas to eliminate the need for expensive Alkaline batteries, which must be replaced periodically.

The fixed-mount units have an external antenna and 12-volt power supply. Their displays and keys are usually much larger and easy to read. Several manufacturers have taken GPS to the next generation by combining cartographic databases (like G-chart, C-map and Navionics) with plotting capability. You now have the ability to see your GPS position relative to the high-quality marine chart database.

Most GPS units on the market can interface with differential-GPS. These units are referred to as "Differential Ready". Differential-GPS is a system provided by the Coast Guard to improve the accuracy of GPS. The differential system uses existing transmitters from the Radio Beacon System (RBS) to offset the margin of error created by "Selective Availability". Currently, there are active transmitters positioned to provide coverage to the East, West, and Gulf Coasts of the nation, as well as the Mississippi River and Great Lakes regions. The system continues to evolve, with active stations transmitting at a rate of 100 to 200 bits per second. The DGPS system was declared operational on January 30, 1996. However, before considering an investment in DGPS equipment, be sure it is available in your area.

Now that we've looked at all of the facts, the question still remains, "Which is best for me?" Loran is still a viable system and valuable for regional cruising or fishing because of its repeatability. It still works well in the U.S. and other regions with Loran coverage. However, for real time information and extended cruising, GPS might prove to be your best option.