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Most of us use our GPS to locate our favorite "honey hole", rock pile, or weed bed. So this title may appear to be a silly question. There are three (3) items you need to effectively utilize your GPS. The three tools of navigation are a GPS instrument, a compass, and a map. A lake map, hydrographic chart, USGS Quadrangle map, etc. The problem with a map alone, is it does not tell you where you are. A GPS unit will not tell you what direction you are headed, if you are not moving. A compass will not give you anything other than direction. These three items are of utmost importance when coordinated together. Not only are they important for knowing where you are and not getting lost, they are important for operating your vessel in a safe and worry free manor in darkness or in fog. May 1, 2000 President Clinton ordered the U.S. military to turn off the Selective Availability that has been degrading the accuracy of civilian GPS units. Selective Availability was the Federal Governments intentional degradation of the GPS (Global Positioning System) signals and was turned to zero. The operators of the system said that GPS (with SA on) would get you to within 328 feet of a fishing spot that you saved as a waypoint on your GPS unit 95% of the time. There is some question that it was that far off. Some experts have theorized that it would get you to within 165 feet 95% of the time. Now with SA turned off the average accuracy should be 32.8 feet. Time will tell. This typical error variance is according to a study conducted by the University of Texas. For more information, you may wish to visit the University of Colorado Geographer's Craft website.

What does this really mean to us regular folk? Well, look at it this way. If you were to attend a large rock concert or a huge major sporting event, or left your car parked way out in some field to attend some major event and thought to bring along your GPS, you would be in luck. Prior to May 1st when you left the stands and began looking for your car that you had left in Lot A, assuming you had your GPS in you pocket, it would have taken you to Lot A. Today it will take you to the car next to yours or behind yours. Now to complete this exercise, take out your car keys and punch your door opener. Your lights will come on, horn blow and your doors will open. This is your car. I understand that one of Raytheon Marine's subsidiaries is developing a new form of Differential Global Positioning System (DGPS) called the Wide Area Augmentation System (WAAS). It uses ground stations to correct GPS signals and uplinks the corrections to satellites that broadcast them over GPS frequencies to WAAS-capable receivers. It will provide accuracy to within 8.2 feet of your target. It should be available to recreational users soon. There are no antennas or differential receivers and should only cost about $100.00 more than standard receivers. Now you'll be able to "GO TO" your waypoint and be back on the edge of that cabbage bed or rock pile.

For those of you who have not yet purchased a GPS, let's answer another question first. What is a GPS good for to a person in a fishing boat? GPS stands for Global Positioning System, a network originally built by the United States Department of Defense. Originally intended as a navigational aid for the U.S. military, GPS technology is now being used for everything from tracking ships on the ocean to helping backpackers find their favorite campsites. It is 24 satellites and a GPS instrument that gives your current global position, time of day, date, and altitude. With this information and knowledge of the earth, the instrument can give distances, compass directions, bearings, headings, speeds, cross track distances, time to destination, distance traveled, distance made good, and plot your position on its display. Three satellites are required for a current position computation. One additional satellite is required for adjustments of your GPS instrument computations. The Department of Defense (DOD) operates the GPS. The first satellite was launched in 1978 and the 24th satellite was launched in 1994. The initial budget for the system was 12 billion dollars.

A GPS instrument is a signal receiver and a computer. Expected battery life is 18 to 24 hours of continuous use. Basically, there is no difference in the various units on the market today. They all function the same. Some manufacturers have added certain "bells and whistles" as sales features to attract consumers to their product. Fundamentally, three events are required to find a global position. Your GPS instrument receives a satellite signal that sets its clock to the satellites clock and gives your instrument the satellite's location. Next, your GPS instrument creates the same position signal at the same time as the satellite broadcasts its signal. Then, upon receiving the satellite's position signal that has been delayed by travel time, your instrument computes this delay time by measuring the time necessary to shift the instruments signal to overlie the satellite's signal. The distance to the satellite (~11,000 miles up) is found by multiplying this time shift by the velocity of light (186,000 mi/sec). Through triangulation, your global position is the point in space where three of these distances intersect. The key feature of your GPS is called waypoints. Waypoints are "electronic stepping stones". By punching in a waypoint every time you change course (direction) you will have a "bread crumb trail" to return home on. Think back to when we were kids and learning how to draw. Do you remember the "connect the dots" exercise that when completed made a picture? Well these dots are your waypoints and they connect to plot a straight-line course between dots (waypoints) from your present position to the target. A GPS saves these waypoints as a position defined by its latitude and longitude. If you have properly plotted your waypoints around shallow areas, reefs, islands, etc. your GPS will lead you safely around these hazards in straight-line steps. A safety suggestion: save your waypoints some distance away from any hazards so that you have a wider margin of error should you be passing that hazard at night or in a fog. The importance of your map is that you can mark your waypoints on your map for future reference. If your GPS unit is a chart plotter with an on-screen map, your waypoints can be saved and will appear on the electronic map. I would suggest you name your waypoints because it will be easier to remember them named (stump, rock, etc.) as opposed to #27, #53 etc. Your unit may also have icons to make it somewhat easier to locate your favorite fishing spots and identify your waypoints by name.

Since your list of waypoints will most likely grow over the years it is a good idea to maintain a log of waypoints, especially if you are fishing various bodies of water. Some GPS units can be interfaced with your personal computer as waypoint lists and computer files. Units with this capability will enable you to make backup lists, update files and record a vast amount of pertinent information about each waypoint. Good waypoint management will allow you to download lists to a new GPS or to your fishing buddy's compatible unit.

The bottom line is that with Selective Availability removed, your GPS units are now more accurate. The cost of these units is very reasonable, around $100.00 with out the on-screen maps and other features. Surely the cost is a lot less expensive than a prop, a hull repair or worse yet, a significant boating accident.

Courses in plotting and seamanship are available through the United States Power Squadrons or the U.S. Coast Guard Auxiliary in your area. In addition, your marine insurance company will offer you a discount for completing a boating safety course. For information on a course in your area contact the U.S.Coast Guard at their toll free Info-Line number 1-800-368-5647.