the beauty of GPS :)
Posted by sas on April 29, 2002 at 17:30:57:
In Reply to: GPS Devices posted by Randy S. on April 29, 2002 at 12:53:06:
oh yeah, i use GPS every day for a living- land surveying. my company has 3 units at $50,000 ea. not what you need for playing around with. i also have the little yellow handheld garmin for misc uses.
i believe most all of the handhelds have the same capability to receive satellite signals. they differ with the ability to download map software and perhaps storage size, both mentioned previous.
i NEVER go wheelin without a topo, 7.5 minute. i don't ever rely on just the GPS.
the beauty of it all is how it works and how accurate it can be. the satellites send a radio signal to the receiver at the speed of light. the satellites have 3 atomic clocks on board @ $100,000 ea. the receiver has just a clock similar to a watch. the satellites synchronize the receiver's clock to theirs. the satellite sends the signal and the receiver receives it. the length of time it took is multiplied by the speed of sound to calculate the distance from the satellite to the receiver. a minimum of 4 satellites are needed to calc the position of the receiver.
the handheld units can be located on the earth to within 30 feet or so. the expensive units can be located to within 1/4".