How to Use a GPS: The Basics And Background
Handheld Units and How They Work
So, you've decided to purchase a GPS for some reason.
You're a backcountry traveler perhaps, who wants another form of navigation. Or maybe you're getting into geocaching or simply love gadgets. Some people, like me, purchase a GPS for Search and Rescue work, while others like to download their routes to overlay them on a computerized map, just for the fun of it.
Whatever the reason for using one of these gadgets, you should really start by understanding the basics. The big picture. And that's where I'll begin here, having used a number of different models myself for more than six years while hiking and volunteering for Search & Rescue.
Additional "How To Use A GPS" articles will include discussions on coordinate systems and datums, waypoints and go-tos, and tracks and routes.
A Friendly Word Of Caution
Because Gadgets Can Fail
As they teach us when training for Search & Rescue, one should never bypass solid map and compass skills and go straight to a GPS. Be sure you know how to read a topographic map and use a compass, so you can double-check your position or route and not rely solely on the GPS as you navigate.
Gadgets can fail. Batteries can die, and you may not have any spare. You might drop and break or lose the GPS. Or the signal may not be sufficient for accurate navigation. So don't leave your map and compass at home just because you have a GPS.
Need To Brush Up on Map and Compass First?
- Basic Map And Compass
How to navigate with a map and compass, with an overview of types of maps, compass parts, declination, intersection and resection
Your Experience With A GPS - A couple of questions for you...
Have you ever used a handheld unit?
If You Have Used A Handheld GPS....
What's the most common thing you use it for?
An Overview Of The Global Positioning System
That stuff in the sky that makes our GPSes work....
Both the United States and Russian governments have GPS systems. Here in the U.S., our system used to be scrambled in order to reduce the accuracy for the Russians, once considered our enemy. This was called "Selective Availability," and it was turned off in 2000.
If you're interested in reading more about the end of Selective Availability, see GPS.gov.
Though the GPS system was developed for the military, it now obviously has many civilian uses. And now that Selective Availability has been turned off, the system is much more accurate for you and me.
When using a GPS in the field, it's important to remember that, except for the trip odometer function like that in a vehicle, distances are "as the crow flies" -- in a direct line from point A to point B. They don't take into account necessary turns in your route by trail or road or in order to bypass obstacles.
The U.S. NAVSTAR GPS System
NAVSTAR stands for NAVigation Satellite Timing And Ranging, which was conceived in the 1960s, begun in 1978, and went operational in 1995.
NAVSTAR is made up of a Space Segment, a Control Segment and a User Segment. The Space Segment is the satellites. The Control Segment is comprised of the receivers or dishes on the ground. And the User Segment is you, me and anyone else who holds a GPS unit in his or her hand.
The Space Segment of NAVSTAR is composed of 24 satellites and 2 spares, which orbit 12,000 miles above the Earth. There are six orbital paths, with each orbit taking 12 hours. At any one time, any spot on Earth should have a line of sight to a minimum of 6 satellites in the absence of impenetrable obstacles.
How To Receive A Good Signal
There's more to it than just turning it on....
In order to accurately navigate with a GPS, you need a good line of sight to the satellites so your unit can receive their signals. These signals don't pass through most solid objects, such as trees, canyon walls, bridges or metal roofs. Even your body can block a satellite's signal.
A GPS will work well outdoors in the open and in vehicles, boats and planes as long as there's a good sky view. It should also work well in a tent and under canvas or nylon as long a