GPS ... what is it,

How does GPS work?
GPS stands for Global Positioning satellite. Back in the 1970s the US sent up a number of satellites for the military to help target and coordinate the armed forces. This positioning system has also been used by the public ... And more recently, with the destruction of the SA system, has provided amazing accuracy.

Geo caching
Lately, I've been experimenting with Geo-Caching ... This is a new sport that has come about due to the affordability and accuracy of those new GPS receivers. People across the country hide little treasures, usually tupperware containers containing a logbook and some small prizes, and post the coordinates of the site online for others to find. When you find the cache you take one of the "prizes" and leave one behind. You should also sign in the logbook telling when you found it, tell how many caches you've found in the past and make a little comment.

Satellite stuff
There are 24 satellite in all, with 21 working at the moment and 3 additional ones acting as spares. These satellite put out a timed pulse. A handheld GPS unit can detect these pulses, and by correlating the pulses from 3 or more satellite, can pinpoint location in 3D space. In other words ... A GPs handheld can tell you your latitude, longitude, and height from Sea-level. Neat stuff.

Did you know?
Here's the neat thing ... Not only are these satellite up in space, they are really far out in space. The satellite sit approximately 11,000 miles up in the air. Compare this to an airplane which typically coasts at 5-6 miles up, and the space shuttle itself which flies around 200 miles. Those satellite are really out there. The diameter of the earth is around 4000 miles ... so the satellite are about 3 earth-widths away. Neat! Despite this distance away, the system is incredibly accurate and can give you exact position within 10 feet.

Satellite are pretty amazing things, huh? If you think GPs satellite are cool then consider spy satellite These suckers are so sensitive, that from space, they can determine whether a penny sitting on the ground is heads or tail! Not bad, considering that regular people standing up usually can't tell with the naked eye!