GLOBAL POSITIONING SYSTEMS FOR SPORT AIRCRAFT
Any pilot who has ever been lost, even temporarily, while flying, knows the value of an accurate navigation system. Fortunately, with the availability of inexpensive, small and lightweight global positioning system (GPS) receivers, no traveler, airborne or otherwise, need ever fear of being lost.
Over the years, government and industry have produced a steadily improving succession of radio navigation systems. Up until the early 1990’s, LORAN and VOR navigation provided the backbone of the navigation system around the world. LORAN was used predominantly by boaters and VOR was the tool of aviators. In the 1980’s, aviators began realizing how useful a tool LORAN could be, and aircraft-compatible LORAN receivers became very popular. This popularity was due, in no small measure, to the fact that VOR navigation was tricky to use. Although the VOR system is still the centerpiece of the worldwide aviation navigation system, it is rapidly giving ground to GPS.
GPS has all of the advantages of LORAN, but none of the drawbacks. Simply put, the GPS system is a satellite-based system of transmitters. This constellation of more than twenty- five satellites continuous beams carefully timed signals to every square foot of the earth. GPS receivers “hear” these transmitted signals from space and interpret the signals to provide exact latitude and longitude positions for the receiver. While the satellite signals contain a great deal of data for the GPS receiver to use, the details are not important. It is enough to know, at any given instant, exactly where the receiver is. This data allows a handheld receiver with a simple computer onboard to compare two successive latitude and longitude positions and convert that change in position to heading and speed. Once location, heading and speed are known, a GPS receiver can give the user lots more information.
The original portable GPS receivers manufactured by Magellan were nothing short of a miracle when they were first introduced in the 1980’s. However, by today’s standards, they were incredibly bulky and power-hungry. A modem Garmin Etrex® GPS receiver sells for less than $125, weighs only a few ounces, operates for over twenty hours on two AA batteries, and provides position accuracy to within fifteen feet. Additionally, modem GPS receivers have built- in antennas which are much more sensitive and accurate than those of the early pioneer units. A modem GPS receiver can be used in an aircraft, an automobile, a boat or on the ground. The only requirement is a relatively good view of the sky. However, because the constellation of satellite is arrayed from horizon to horizon on any given day, the instrument panel of an aircraft is a suitable mounting location which will produce a reliable signal in almost every case.
Although permanently-mounted instrument panel GPS receivers are available and widely used in general aviation, kitplane, ultralight, hang glider, paraglider and balloon pilots have almost unanimously adopted the handheld portable GPS receiver as the navigation tool of choice for their aviation activities. There are several reasons. First, handheld GPS receivers are, as explained above, available at very low cost. Additionally, a handheld GPS receiver can be used anywhere, not just in the aircraft. Third, the handheld GPS receivers are every bit as accurate as the expensive panel-mounted units.
Because there are a wide variety of handheld receivers available, it is important to understand the three principle classes of portable GPS units, their benefits and their drawbacks.
The basic, no-frills handheld GPS unit does a marvelous job of navigating. A pnme example is the basic Garman Etrex®. This unit, pictured here, is capable to storing up to 500 user waypoints, provides position, altitude, ground speed, bearing to destination, course over the ground, time to destination, distance off-course, and direction to steer. It also provides an ongoing chart function of the course which the pilot has flown. In short, the basic unit provides to the pilot all the necessary navigation functions required, at a very low cost. Its only drawback is it contains no data when new, and those places that the pilot wants to visit need to be entered into the unit in latitude and longitude format, or by saving a known position simply by virtue of being located at that position. The storage of waypoints in GPS units is very simple to do, so you should not be discouraged by this limitation. However, keep in mind that a non-database GPS unit like the basic Etrex is not capable of storing anything other than waypoint names and position, and it is only these waypoints which will be displayed on the liquid crystal display of the unit when it is in use. This display also can be switched to show exact position and navigation information at any time with the touch of a button.
The next step up in performance are basic database GPS receivers. Basic database GPS receivers come preprogrammed with waypoints, and sometimes, with information about those waypoints. For example, the Garman Venture®, has a database of all small, medium and large cities in the United States and Canada already loaded. In addition, the user can store up to 500 more of his or her own special waypoints to compliment the built-in database. The Venture also permits the user to connect the receiver to a personal computer and transfer up to one million bites of additional data.
The next step up the chain of performance are database units, like th Garmin Legend shown at right, which have built-in ground maps showing lakes, rivers, roads, railroads, major towns and cities, and sometimes other points of interest like restaurants, museums and stadiums. It is possible to navigate from the air by following the map displayed on the screen, much like having an aeronautical chart onboard. Another model of this type of receiver is the Garmin Vista®, which also includes a true barometric altimeter and magnetic compass.
An important limitation of all of the previously described GPS units is that they are not specifically designed for aviation. Rather, they are “all purpose” units. Garmin (as well as others) also produce aviation specific GPS units such as the Garmin Pilot III . GPS receivers like the Pilot III contain a ground map database, and an airport database as well. All public and most private airports in the world are contained within the Garman Pilot database. In addition to the airport location appeanng on the ground map display, all critical data regardingthe airport’s facilities are stored and available for the pilot to use. This information includes radio frequencies, field elevation, runway lengths, orientation, runway lighting, services and fuel types available, nearest restaurants and more.
While these are handy features, to be sure, they come with a price: A handlield GPS unit which contains a complete ground map database of North America can be purchased for less than $250. A GPS with the aviation database will cost over $500.
For almost all recreational pilots, the non-aviation specific GPS units will more than fulfill all of the pilot needs, since recreational pilots seldom fly into controlled airports or controlled airspace, and even if they do, can always rely on a conventional aeronautical chart for the otherwise expensive database of the aviation-GPS.
Most pilots will find that mounting and powering GPS units in their sport aircraft is easily accomplished. Most haudheld GPS manufacturers provide a wide variety of accessories, including different mounts and power cords. Strictly speaking, however, external power cords are a bit of a luxury with most handheld GPS’s, since their batteries last so long. Most of the Garmin GPS’s described above, for example, are good for more than twenty hours of flight time. Also, don’t be worried about losing the data which you may have stored in one of these units when changing batteries. A special “keep alive” battery built into the system preserves a GPS memory, even while you change the batteries.
One of the truly remarkable features of all of these units is their incredible accuracy. In modern GPS units, by way of example, if you store a spot in front of your hanger as your home waypoint (you can name it “home” if you want), fly a hundred miles and then taxi back to your hanger, the position reported on the GPS when you return will be within fifteen feet of the mark originally placed on your GPS for that point. In the air, if your GPS says that you are going 61 miles per hour, you can be sure that it is exactly 61 miles per hour, not 61.5. Most of the units sold today are waterproof, so are usable in almost any weather. Most are back-lighted so that they will work at night. And, perhaps most important, most have very simplified controls, making their keypads easy to use and quick to learn.
In short, in this day, there is no reason not to be flying with GPS.
3
Any pilot who has ever been lost, even temporarily, while flying, knows the value of an accurate navigation system. Fortunately, with the availability of inexpensive, small and lightweight global positioning system (GPS) receivers, no traveler, airborne or otherwise, need ever fear of being lost.
Over the years, government and industry have produced a steadily improving succession of radio navigation systems. Up until the early 1990’s, LORAN and VOR navigation provided the backbone of the navigation system around the world. LORAN was used predominantly by boaters and VOR was the tool of aviators. In the 1980’s, aviators began realizing how useful a tool LORAN could be, and aircraft-compatible LORAN receivers became very popular. This popularity was due, in no small measure, to the fact that VOR navigation was tricky to use. Although the VOR system is still the centerpiece of the worldwide aviation navigation system, it is rapidly giving ground to GPS.
GPS has all of the advantages of LORAN, but none of the drawbacks. Simply put, the GPS system is a satellite-based system of transmitters. This constellation of more than twenty- five satellites continuous beams carefully timed signals to every square foot of the earth. GPS receivers “hear” these transmitted signals from space and interpret the signals to provide exact latitude and longitude positions for the receiver. While the satellite signals contain a great deal of data for the GPS receiver to use, the details are not important. It is enough to know, at any given instant, exactly where the receiver is. This data allows a handheld receiver with a simple computer onboard to compare two successive latitude and longitude positions and convert that change in position to heading and speed. Once location, heading and speed are known, a GPS receiver can give the user lots more information.
The original portable GPS receivers manufactured by Magellan were nothing short of a miracle when they were first introduced in the 1980’s. However, by today’s standards, they were incredibly bulky and power-hungry. A modem Garmin Etrex® GPS receiver sells for less than $125, weighs only a few ounces, operates for over twenty hours on two AA batteries, and provides position accuracy to within fifteen feet. Additionally, modem GPS receivers have built- in antennas which are much more sensitive and accurate than those of the early pioneer units. A modem GPS receiver can be used in an aircraft, an automobile, a boat or on the ground. The only requirement is a relatively good view of the sky. However, because the constellation of satellite is arrayed from horizon to horizon on any given day, the instrument panel of an aircraft is a suitable mounting location which will produce a reliable signal in almost every case.
Although permanently-mounted instrument panel GPS receivers are available and widely used in general aviation, kitplane, ultralight, hang glider, paraglider and balloon pilots have almost unanimously adopted the handheld portable GPS receiver as the navigation tool of choice for their aviation activities. There are several reasons. First, handheld GPS receivers are, as explained above, available at very low cost. Additionally, a handheld GPS receiver can be used anywhere, not just in the aircraft. Third, the handheld GPS receivers are every bit as accurate as the expensive panel-mounted units.
Because there are a wide variety of handheld receivers available, it is important to understand the three principle classes of portable GPS units, their benefits and their drawbacks.
The basic, no-frills handheld GPS unit does a marvelous job of navigating. A pnme example is the basic Garman Etrex®. This unit, pictured here, is capable to storing up to 500 user waypoints, provides position, altitude, ground speed, bearing to destination, course over the ground, time to destination, distance off-course, and direction to steer. It also provides an ongoing chart function of the course which the pilot has flown. In short, the basic unit provides to the pilot all the necessary navigation functions required, at a very low cost. Its only drawback is it contains no data when new, and those places that the pilot wants to visit need to be entered into the unit in latitude and longitude format, or by saving a known position simply by virtue of being located at that position. The storage of waypoints in GPS units is very simple to do, so you should not be discouraged by this limitation. However, keep in mind that a non-database GPS unit like the basic Etrex is not capable of storing anything other than waypoint names and position, and it is only these waypoints which will be displayed on the liquid crystal display of the unit when it is in use. This display also can be switched to show exact position and navigation information at any time with the touch of a button.
The next step up in performance are basic database GPS receivers. Basic database GPS receivers come preprogrammed with waypoints, and sometimes, with information about those waypoints. For example, the Garman Venture®, has a database of all small, medium and large cities in the United States and Canada already loaded. In addition, the user can store up to 500 more of his or her own special waypoints to compliment the built-in database. The Venture also permits the user to connect the receiver to a personal computer and transfer up to one million bites of additional data.
The next step up the chain of performance are database units, like th Garmin Legend shown at right, which have built-in ground maps showing lakes, rivers, roads, railroads, major towns and cities, and sometimes other points of interest like restaurants, museums and stadiums. It is possible to navigate from the air by following the map displayed on the screen, much like having an aeronautical chart onboard. Another model of this type of receiver is the Garmin Vista®, which also includes a true barometric altimeter and magnetic compass.
An important limitation of all of the previously described GPS units is that they are not specifically designed for aviation. Rather, they are “all purpose” units. Garmin (as well as others) also produce aviation specific GPS units such as the Garmin Pilot III . GPS receivers like the Pilot III contain a ground map database, and an airport database as well. All public and most private airports in the world are contained within the Garman Pilot database. In addition to the airport location appeanng on the ground map display, all critical data regardingthe airport’s facilities are stored and available for the pilot to use. This information includes radio frequencies, field elevation, runway lengths, orientation, runway lighting, services and fuel types available, nearest restaurants and more.
While these are handy features, to be sure, they come with a price: A handlield GPS unit which contains a complete ground map database of North America can be purchased for less than $250. A GPS with the aviation database will cost over $500.
For almost all recreational pilots, the non-aviation specific GPS units will more than fulfill all of the pilot needs, since recreational pilots seldom fly into controlled airports or controlled airspace, and even if they do, can always rely on a conventional aeronautical chart for the otherwise expensive database of the aviation-GPS.
Most pilots will find that mounting and powering GPS units in their sport aircraft is easily accomplished. Most haudheld GPS manufacturers provide a wide variety of accessories, including different mounts and power cords. Strictly speaking, however, external power cords are a bit of a luxury with most handheld GPS’s, since their batteries last so long. Most of the Garmin GPS’s described above, for example, are good for more than twenty hours of flight time. Also, don’t be worried about losing the data which you may have stored in one of these units when changing batteries. A special “keep alive” battery built into the system preserves a GPS memory, even while you change the batteries.
One of the truly remarkable features of all of these units is their incredible accuracy. In modern GPS units, by way of example, if you store a spot in front of your hanger as your home waypoint (you can name it “home” if you want), fly a hundred miles and then taxi back to your hanger, the position reported on the GPS when you return will be within fifteen feet of the mark originally placed on your GPS for that point. In the air, if your GPS says that you are going 61 miles per hour, you can be sure that it is exactly 61 miles per hour, not 61.5. Most of the units sold today are waterproof, so are usable in almost any weather. Most are back-lighted so that they will work at night. And, perhaps most important, most have very simplified controls, making their keypads easy to use and quick to learn.
In short, in this day, there is no reason not to be flying with GPS.
3
