GPS navigation involves a combination of technology and traditional
location techniques. There are a variety of GPS receivers designed for
use in the air, on the land, or on water. And how you navigate depends
on your experience, the kind of trip you take, and the capabilities
of your GPS unit.
How to Use GPS
Unless you're solely an gadget addict, you want a GPS unit as an aid
to finding your way when making a trip. And if you want to use a specific
GPS model, the owner's manual will tell you how. But there's a difference
in knowing how to use GPS and how to make GPS useful.
If the only traveling we did was on highways, there would be little
need for GPS. But if you're off road, flying, or on the water,
a GPS device can provide directional information similar to road signs.
In addition to a receiver, GPS navigation requires a map and probably
a compass. GPS can provide your direction, but only when you're moving.
Most GPS units are capable of displaying an electronic map
and some also come with an electronic compass built in. If you need to know your
altitude with precision, either get a separate altimeter or a barometric sensor
as part of the GPS receiver. An advantage to having a separate map and compass
is that they're still usable if the batteries in your GPS receiver die.
Even GPS units that can't store regular electronic maps, let you create your own
simple map by storing reference locations called, "waypoints".
Each waypoint is identified by its location, along with a name and usually a symbol.
For instance, you might be hiking and find a cave you'd like to explore
at later time. The GPS receiver would determine your position and save the
location with either a name you chose, or an automatically generated one, as a
waypoint. Then later at a different location, the GPS unit could calculate
the distance and direction from your present position to the cave waypoint.
Most GPS receivers have enough memory to store anywhere from 100 to 1000
Just as a map isn't made of a single point, any GPS path you want
to take probably needs more than one waypoint. A "route" is a group
of waypoints that show a path you plan to take. And a "track" is the
path of waypoints that you actually followed. Routes and tracks are
stored by the GPS receiver with the waypoints and called a "track log".
How to Use a GPS Receiver
Each GPS device is operated somewhat differently, depending on the
make and its functions. But GPS units do have certain operations
in common. You need to set the receiver for the coordinate system
and datum of the map you're using. You also need to "initialize"
the receiver. Initialization is the GPS unit finding the local
satellites and gathering location information. Since you could
be starting anywhere in the world, it takes longer to acquire and
process the satellite data than for subsequent position readings. Some
receivers speed up the initialization process by having you input your
approximate location and time. The receiver may also have to be initialized
if it was moved several hundred miles since its last use.
Once a GPS receiver is initialized, it can display data about
the satellites its tracking. The information includes which satellites
are supplying signals, where they are and some estimate of position accuracy. Modern GPS
units have 12 parallel channels which means they can simultaneously track up to
12 satellites. The more satellites used, the more accurate the
positioning can be, but it's rare to have access to more than 10 at one
time. The receiver will indicate your position and after you move to a new
location, it can show your distance, direction and speed from
your last position. After initialization you're ready to follow a map or your own
route of waypoints to your destination.