Global Positioning System receivers, or GPS for short, are much more than mere “toys”. They are serious navigation tools that no Jeeper should be without. They are much better than traditional paper maps, because they are interactive, and today’s GPS units are very accurate. GPS units are able to show your position based on input from satellites, as you move, on an electronic map, and also to track your progress so you can easily see where you’ve been, and retrace your steps if necessary.

A Brief History Of GPS Receiver Accuracy:

• 100 meters: Accuracy of the original GPS system with SA (Selective Availability¹).
• 15 meters: Typical GPS position accuracy without SA.
• 3-5 meters: Typical differential GPS (DGPS²) position accuracy.
• < 3 meters: Typical WAAS³ position accuracy

Magellan Meridian Platinum GPS Features:

• WAAS-Enabled Accuracy
• Large, Easy-To-Read Screen
• Well-Designed, One-Handed Operation
• Detailed Basemap of Highways, Cities, Major Waterways, and More
• Interchangeable Memory Cards Allowing Up To 64MB of Additional Map Information At A Time
• Electronic Compass That Works Even When You Are Standing Still⁴
• Built-In Barometer for Tracking Weather Trends
• Rugged Design With Rubber Armoring and High Impact Plastic Body That Is Weatherproof And Floats
• And Much More!

There are 24 satellites orbiting the earth about 11,000 miles above us in six different orbital planes that make up the GPS network. These satellites are constantly moving. They make a complete orbit in approximately 12 hours, which means they are traveling at speeds of roughly 7,834 miles an hour. Like other satellites, GPS satellites are powered by solar cells that absorb energy from the sun.

GPS satellites send out a low-power signal to non-military GPS receivers at 1575.42Mhz in the UHF band. These satellites are positioned in orbit in such a way that at least 4 of them should be visible to your receiver at any given time from any location on Earth. It is important to note that your GPS unit must be receiving a signal from at least three satellites at the same time to funtion (unlike most GPS units, the compass will continue to function on the Meridian Platinum even if NO satellites are visible).

Your GPS receiver uses these low power satellite signals to triangulate your position. It needs to receive data from at least 3 satellites simultaneously to calculate your position without elevation, and data from a minimum of 4 satellites with elevation. The software contained within your GPS receiver can then mark this position on its map screen to display your current position to you in a manner that is easy to understand.

GPS Benefits to a Jeeper:

If you’ve never been lost while 4-wheeling, consider yourself lucky – I’ve been lost (before I owned a GPS), and it’s not much fun. There have been many times that I found myself exploring old dirt roads and trails that couldn’t be found on a map, and after so many forks and crossroads throughout one or more days, it can be hard to remember the way back home. The GPS unit – in this case a Magellan Meridian Platinum – has the ability to track your progress by leaving “electronic breadcrumbs” on its map, making it easy to see where you’ve been, and easy to backtrack the way you came. Another way to mark your trail is by setting Waypoints on your GPS receiver's map at key points along your trip. A Waypoint is an electronic “marker” that sets the Latitude and Longitude of your position on the electronic map, and usually allows you to assign it an icon, a name, and a text message. As a general rule, I do not rely solely on the “breadcrumb” trail to find my way back. I also mark the beginning of the trail, the end of a trail, and important features along the way, such as forks in the road, obstacles, and landmarks, as Waypoints for later reference.

1. SA: Selective Availability was a deliberate inaccuracy of the GPS signal to prevent civilian receivers from being used in a military attack on the U.S.
2. DGPS: Differential GPS uses local reference stations to improve the accuracy of your position.
3. WAAS: Wide Area Augmentation System. WAAS is made up of a system of satellites and ground stations that send signal corrections to your GPS receiver.
4. Electronic Compass: GPS receivers without an electronic compass must determine a heading by tracking your movement.

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Dirt Road Magazine is sponsored by Turner 4WD Parts Co.