Page Button Click Stick On/Off Button The Satellite Page provides a picture of satellite signal tracking, telling you when your unit is ready for navigation and shows your location coordinates. The Sky view graphic represents a view looking up at the sky from your current location showing satellites and their assigned numbers. Signal strength bars for each satellite are shown just below the sky view. Satellites and their signals appear as hollow shapes until a signal is received and then they appear darkened in. The Stronger the signal, the taller the signal bar. When differential correction data (from waas) has been received for GPS satellites numbered 32 or below, a “d” displays in the signal bar beneath the sky view. Outer Ring – Satellites on Horizon Inner Ring – Satellites within 45° angle from vertical Center – Satellites overhead The status window tells you when you are ready to navigate and gives you your accuracy reading. Also, this page gives you your current location and your elevation. However, elevation is the most inaccurate part of GPS technology. You can manually enter in a new location if you are more than 600 miles from where you last used the unit. This gives the unit reference info and speed satellite acquisition. All you have to do is select “new location” from the options menu and then the “use map” options to approximate your position. You can also manually enter a new, more accurate elevation, if know, to increase position accuracy. Go to the Options Menu and select Use with GPS Off to use your units inside. Otherwise your unit will continue to search for satellites even through it will not receive a signal inside a building. When you go outside, you will want to go back to the options menu on the satellite screen to turn the GPS back On.

GPS Basics Trying to figure out where you are and where you're going is probably one of man's oldest pastimes. Navigation and positioning are crucial to so many activities and yet the process has always been quite cumbersome. Over the years all kinds of technologies have tried to simplify the task but every one has had some disadvantage. Finally, the U.S. Department of Defense decided that the military had to have a super precise form of worldwide positioning. And fortunately they had the kind of money ($12 billion!) it took to build something really good. The result is the Global Positioning System, a system that's changed navigation forever.

GPS uses these "man-made stars" as reference points to calculate positions accurate to a matter of meters. In fact, with advanced forms of GPS you can make measurements to better than a centimeter! In a sense it's like giving every square meter on the planet a unique address. GPS receivers have been miniaturized to just a few integrated circuits and so are becoming very economical. And that makes the technology accessible to virtually everyone. These days GPS is finding its way into cars, boats, planes, construction equipment, movie making gear, farm machinery, even laptop computers. Soon GPS will become almost as basic as the telephone. Indeed, at Trimble, we think it just may become a universal utility. The Global Positioning System (GPS) is a worldwide radio-navigation system formed from a constellation of 24 satellites and their ground stations.

Earth Circumference 24,000 Miles Rotation 1,000 Miles/Hour 1 Day Cycle

GPS Satellites Distance from Earth ½x Earth’s Circumference 12,000 Miles 2 Orbits in 24 Hours Travel 7,000 Miles/Hour Powered by Solar Energy

How GPS Works Here's how GPS works in five logical steps: 1. The basis of GPS is "triangulation" from satellites. 2. To "triangulate," a GPS receiver measures distance using the travel time of radio signals. 3. To measure travel time, GPS needs very accurate timing which it achieves with some tricks. 4. Along with distance, you need to know exactly where the satellites are in space. High orbits and careful monitoring are the secret. 5. Finally you must correct for any delays the signal experiences as it travels through the atmosphere.

Signal Transmission When you are using your GPS Unit, you want to make sure that you are receiving a correct and accurate signal. These are some of the errors that can be received by your GPS unit. In order to make sure that you do not get blocked signals or multi-path errors, make sure that you are out in the open and not in a canyon, under trees, or next to tall buildings.

Student Map

Tree & Plant Identification GPS Applications Tree & Plant Identification Science & Technology Bicycle Safety

GPS Applications High Adventure Fishing & Canoeing Science & Technology

Environmental Education GPS Applications Wildlife Mapping Environmental Education Earth Science

Geocashing A Treasure Hunt!

http://www.earthcache.org/

Credits How Stuff Works http://electronics.howstuffworks.com/gps1.htm - 4H Navigation to Success by Brady Mitchell - All About GPS http://www.trimble.com/gps/ - Tracks4Africa http://www.tracks4africa.co.za/# - EARTHCACHE http://www.earthcache.org/