[Fudd]

GPS does not bounce signals off of satellites. GPS is a receiver that gets a timed signal from at least three of 32 satellites for 2D(lat-long) position fix and at least four for 3D(lat-long-altitude). GPS is deadly accurate, and the potential for governmental mischief is certainly there.
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And from the U.S. Navy comes this little ditty... "Precise Positioning Service is for the DOD only. Only Standard Positioning Service (SPS) is available to the public. With SPS, 100 meter accuracy is observed 95% of the time. The following plot shows SPS information gathered at USNA over a 6 hour period. Notice the brief 4 minute excursion over 1/2 mile at 14 knots for our fixed building!" You bet the state will want you to pay for the GPS drift, too. LINK

[j_tull]

Better check the date on your source, Selective Availablility was removed a couple of years ago.