GPS: What is it & how does it work?

GPS stands for Global Positioning System. This system represents a constellation of 24 satellites operated by the U.S. Department of Defense. These satellites travel in controlled orbits approximately 19,300 kilometres above the earth’s surface, making two complete rotations every day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites “visible” in the sky. Each satellite transmits a complex radio signal including an extremely accurate time signal. Using a GPS receiver (from recreational devices to survey-grade instruments) satellite radio signals are received and simple trigonometry calculations determine a precise position on the earth’s surface. A minimum of 3 satellite signals is required but most GPS units can access up to 12 or more for increased accuracy.

Constellation of GPS satellites and their orbits. (McNamara, 2004)

Geocaching: What is it & how does it work?

Geocaching is a high-tech treasure hunt designed for recreational GPS users. Participating in a cache hunt is a great way to get some exercise in the great outdoors while taking advantage of the wonderful features and capabilities of a GPS unit. The basic premise of geocaching is to have individuals or organizations set up caches all over the world, then share the coordinate location with others on the Internet. When you find a cache in your area, enter the coordinates on your GPS and off you go on a treasure hunt! If you find a cache, sign the log book, take a piece of the treasure, leave a piece of treasure then go home and post your experience on geocache.com!!

(Modified from www.geocaching.com)

What is a "cache"?

Taken from the camping/hiking term meaning a hiding place for concealing provisions. In this sport, it could be anything from a scenic location to a film canister with a log book to a tupperware container holding all kinds of goodies!

Tips for Geocaching

1. Visit geocaching.com to get coordinates for a cache site to hunt.
2. Create a ‘waypoint’ on your GPS and edit the coordinates to match those provided on the website.
3. Use the “Nav” or “Go to” function on your GPS to navigate to the cache site.
4. Use the clues provided by the cache description to locate the cache.
5. Sign, date and comment in the log book found with the cache.
6. Trade a piece of the bounty for something equally unique.
7. Be sure to log your find on geocaching.com

Try the Brock geocaching challenge here! Happy caching!!

For more details about geocaching or to find additional caches in your area, please visit www.geocaching.com

Resources

1. Fun with GPS, Donald Cooke, 2005. MapBk G 109.5 C645 2005
2. GPS for DUMMIES, Joel McNamara, 2004. MapBk G 109.5 M365 2004
3. Geocaching for DUMMIES, Joel McNamara, 2004. MapBk G 109.5
4. Map Use & Analysis, John Cambell, 1991. MapBk GA 105.3 C357 1991
5. The Complete Idiot's Guide to Geocaching, Jack W. Peters, 2004. Map Library office
6. “How Stuff Works” http://electronics.howstuffworks.com/gps.htm
7. “GPS: the New Navigation” http://www.pbs.org/wgbh/nova/longitude/gps/gps05.html
8. “Geocaching.com” http://www.geocaching.com/