You might have seen the television commercial with the suburban family who drove their sport utility vehicle to Tibet (actually some idealized rugged outdoor location) for a picnic and the inept dad locks the keys in the car. Saving the day, is a generation X customer service representative who locates the car from a far off high tech data-center. Satellites locate the car, unlock the door, saving the family picnic!

The space age technology seamlessly working behind the scenes in this scenario is GPS or Global Positioning System. GPS is a satellite locating system developed by the military, which is now available to the general public. GPS units locate a specific point on the earth through the low frequency radio communication with a minimum of 4 satellites of the 24 GPS satellites orbiting the earth. Location is determined by comparing the time for the radio signal to travel from the satellite...