There's another permutation of DGPS, called
"inverted DGPS," that can save money in certain tracking applications.
Let's say you've got a fleet of buses and you'd like to pinpoint them on street maps
with very high accuracy (maybe so you can see which side of an intersection they're parked
on or whatever).
Anyway, you'd like this accuracy but you don't want to buy expensive
"differential-ready" receivers for every bus.
With an inverted DGPS system the buses would be equipped with standard GPS receivers
and a transmitter and would transmit their standard GPS positions back to the tracking
office. Then at the tracking office the corrections would be applied to the received
It requires a computer to do the calculations, a transmitter to transmit the data but
it gives you a fleet of very accurate positions for the cost of one reference station, a
computer and a lot of standard GPS receivers. Such a deal!
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