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To: Myrddin
So the xmission is passive, I should have read your post detailing the parity situation better.

The broadcast is constant...just need the right stuff to tap into it.

The only thing that could xmit your location would be your receiver? There are no logs of data aquisition generated by the sat?

And finally, are the PN's unique to each receiver or are they floating liscenses?

EBUCK
103 posted on 01/02/2003 5:15:56 PM PST by EBUCK
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To: EBUCK
GPS is entirely passive to the end user. Your receiver contains 1 to 12 receivers that are tracking the PN chipping sequences of the satellites known to be visible. If you do a "cold start" with no clue about your location or time, you can work through a series of PN choices until you lock one. Once the first one is locked, you can use it to download an almanac and set your time. You look at the location of the satellite that you successfully locked vs the almanac data, then try another PN sequence of a satellite that should be visible. You continue doing that until you have 3 or 4 satellites "locked". At that point, you can calculate a fix.

The PNs of the satellites currently launched are usually in the ROM of the receiver. You can update your GPS firmware with many of the higher quality units. This 'cache' of good PN prospects is only needed as a starting point. The almanac will contain the whole list of current satellites...including ones that are newer than your firmware.

114 posted on 01/02/2003 5:32:48 PM PST by Myrddin
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