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Response to Yonnie3 (Reply #4)

Sat Jan 12, 2019, 08:20 PM

5. Right. But, there has to be some reference to know where the Earth is in it's rotation.

Last edited Sat Jan 12, 2019, 09:51 PM - Edit history (2)

Otherwise all we would know is where you are on a blank sphere. So the ultimate reference must be those cesium atoms running GMT plus your local time. So why the need for the accurate mag var ?

On edit: Since I've only worked on simulated GPS on simulators, I emailed a friend who worked on GPS well before the general public had access to receivers. He was working on a civilian version receiver for tracking vehicles. I hope I don't need to feed him too many beers to get the answer.

Another edit: It's been a long time since I worked on GPS, but from my memory, even the simulated ones had to satisfy the avionics. I think the satellites sent their positions in polar co-ordinates and the satellite would get that position from an INS type of system. But none of this explains the need for the mag var which was the reason for the post in the first place.

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Replies to this discussion thread
Arrow 5 replies Author Time Post
Eugene Jan 2019 OP
Yonnie3 Jan 2019 #1
LakeSuperiorView Jan 2019 #2
rickford66 Jan 2019 #3
Yonnie3 Jan 2019 #4
LineLineLineLineNew Reply Right. But, there has to be some reference to know where the Earth is in it's rotation.
rickford66 Jan 2019 #5
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