What They Can Do





The Global Positioning System, a collection of 24 Earth-orbiting satellites, has a number of possible applications, spanning across several areas of society. For most of us, the way we can take advantage of GPS is to purchase a handheld GPS receiver, or have one installed in our car. Handheld receivers are compact, and the most basic ones are fairly affordable. You can pick one up for as low as $100!

This could certainly be a sensible purchase, when you consider all of the things a GPS receiver can do for you. The basic function of a GPS receiver is to figure out its location on Earth. To everyone who's ever lost their way in the woods, driven off course on a cross-country trip or gotten turned around while piloting a boat or airplane, the advantages of this simple function are obvious. But most GPS receivers go far beyond providing this simple navigational data. They can act as an interactive map, and they have a number of recreational applications.

The Basics
 At its heart, a GPS receiver is simply a device that can locate itself on Earth. It does this by communicating with at least four satellites overhead (see this page for details). For this reason, a GPS receiver is limited as to where it can function. It has to be able to "see" the satellites to calculate latitude and longitude, which means it usually won't work inside. So, one of the basic characteristics of GPS receivers is that they find your location only when you are outside.

The simplest GPS receiver would give you just the coordinates of your location on Earth in latitude, longitude and altitude. Latitude and longitude are basically X and Y axes of a big imaginary grid wrapped around the planet, and altitude is a measure of your distance above sea level. If you had a GPS receiver that gave you these simple coordinates, and you had a map of your area that used this same coordinate system, you could find your location simply by reading the map. In this regard alone, a GPS receiver is a amazing device. Without a GPS receiver, you would have to find your position based on the position of the stars in the sky, using complicated tools and calculations. And you wouldn't have near the same level of accuracy!

But today's handheld GPS receivers give you much more than this raw data. Even low-end receivers have some sort of electronic map stored in memory, so you don't have to carry around a bunch of paper maps. The receiver takes the coordinate information and applies it to its electronic map, graphically pointing out to you where you are in relation to roads, bodies of water, etc. Maps vary a great deal in the level of detail they offer; but the basic idea behind this function is to give you a map that automatically marks your location, without you having to consider your coordinates. This is a great convenience any time you need to use a map, and is extremely helpful at times when you can't take the time to find your location on a map, such as when you're driving down the highway.

GPS in Motion
 A standard GPS receiver will not only place you on a map at any particular location, but will also trace your path across a map as you move. If you leave your receiver on, it can stay in constant communication with GPS satellites to see how your location is changing. If you've read How It Works, you know that a receiver must know the exact time to find its location. If it combines these two pieces of information -- your changing location and the exact time -- it can also calculate how fast you are going. A receiver can use all of this basic data to give you several pieces of valuable information:

To obtain this last piece of information, you would have to have given the receiver the coordinates of your destination, which brings us to another GPS receiver capability: inputting location data.

User Input
 Most receivers have a certain amount of memory available for you to store your own navigation data. This greatly expands the functionality of the receiver, because it essentially lets you make a record of specific points on Earth. The basic unit of user input is the waypoint. A waypoint is simply the coordinates for a particular location. You can save this in your receiver's memory in two ways:

This capability lets you use your GPS receiver in a number of different ways. You can record any specific location that interests you, so that you'll be able to find it again at a later time. This might include: You can also combine a series of different waypoints to form a route. One way to use this function is to periodically record waypoints as you make a trip so that you can backtrack, or follow the same route again on another trip. And route-mapping also lets you plan ahead. When you have time to examine a map at home, you can record a series of waypoints along the roads or trails that lead to your destination. Then, when you are traveling, all you will need to find your way is your GPS receiver. As you travel, the receiver will show you which way to go and give you the distance to your next waypoint. All you need to do is follow its simple directions.

Computer Connections
Receivers with route capabilities will let you save a certain number of waypoints to memory so that you can use them again and again. If the receiver has a data port, you can also download your routes to a computer, which has much more storage memory, and then upload them again when you plan to follow those routes.

Because they have so much more storage capability, computers can do a lot more with GPS location data than your average receiver. A receiver with a data port can feed the raw coordinates of your location into a computer running more complicated software. There are a number of available software applications that can place you on detailed maps of particular areas. If you want to use your receiver for complicated navigation, down backroads for example, this capability will help you out tremendously. You can also update your computer maps, so that they include any surveying adjustments or changes in an area, whereas a receiver's onboard map usually can't be changed. When you use your receiver in conjunction with your computer, you increase the receiver's capabilities considerably. Also, your receiver won't be outdated as quickly, because in conjunction with a computer, all it needs to do is provide coordinates -- your computer does the rest.

Some recent receivers let you download detailed maps of an area into the GPS, or supply detailed maps with plug-in map cartridges. These maps can give you street-level detail in cities and the receiver may even provide driving directions as you drive!

GPS receivers have been a favorite of hikers, boaters and pilots for years, and are now becoming commonplace as prices fall. Check out the handy feature chart to help you decide which features you need!

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