Here’s how it works. Geocachers seek out hidden treasures utilizing GPS coordinates posted on the Internet by the people hiding the cache. So to geocache, you’ll need a handheld GPS receiver. GPS, which stands for Global Positioning System, is the only system today able to show you your exact position on the Earth anytime, in any weather, anywhere. GPS satellites, 24 in all, orbit at over 11,000 miles above the Earth.
The satellites transmit signals that can be detected by anyone with a GPS receiver. Using the receiver, you can determine your location with great precision. But just as important, you’ll be able to locate other things too, such as a GEOCACHE! Remember, most smart phones include a GPS receiver, so you may have all the equipment you need.
If your phone doesn't have a GPS receiver, there are a variety of GPS receiver models to choose from starting at about $26 and range up to $185. You can check out a selection here on Amazon, but they're available in most places that carry electronics, so be sure to “shop” for the one you like best and has the best price. GPS Models