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Will your GPS go mad in April?

Jm_

sled dog's bollocks
Jan 14, 2002
18,853
9,557
AK
Fun fact, most people think GPS sats send out "position" data, when in fact they are flying at 20,000mph or whatever and have no idea where they are, they send out atomic time and the receiver calculates the actual time that "makes sense" based on the delays of four sats as the signal passes through the atmosphere. Four equations with four unknowns and differential eq math gets you a 3d position.
 

KenW449

Thanos did nothing wrong
Jun 13, 2017
2,704
329
Floating down the whiskey river...
Fun fact, most people think GPS sats send out "position" data, when in fact they are flying at 20,000mph or whatever and have no idea where they are, they send out atomic time and the receiver calculates the actual time that "makes sense" based on the delays of four sats as the signal passes through the atmosphere. Four equations with four unknowns and differential eq math gets you a 3d position.
Technically, they only need 3 sats for positioning.
 

jdcamb

Tool Time!
Feb 17, 2002
19,799
8,383
Nowhere Man!
Fun fact, most people think GPS sats send out "position" data, when in fact they are flying at 20,000mph or whatever and have no idea where they are, they send out atomic time and the receiver calculates the actual time that "makes sense" based on the delays of four sats as the signal passes through the atmosphere. Four equations with four unknowns and differential eq math gets you a 3d position.
Wrong. you should never put Ketchup on eggs and hotdogs, under any circumstance. How do magnets work under water then?
 

Jm_

sled dog's bollocks
Jan 14, 2002
18,853
9,557
AK
Technically, they only need 3 sats for positioning.
Depends on whether you want to know your altitude, that's considered part of "position" in my line of work, but when describing GPS people tend draw the "3 circles" and "where they intersect" is where you are, that's not even close to how it operates.
 

Toshi

Harbinger of Doom
Oct 23, 2001
38,032
7,553
Depends on whether you want to know your altitude, that's considered part of "position" in my line of work, but when describing GPS people tend draw the "3 circles" and "where they intersect" is where you are, that's not even close to how it operates.
One could envision time offsets as defining radii, then the analogy seems to make sense if a bit tortured.
 

Full Trucker

Frikkin newb!!!
Feb 26, 2003
10,484
7,531
Exit, CO
Fun fact, most people think GPS sats send out "position" data, when in fact they are flying at 20,000mph or whatever and have no idea where they are, they send out atomic time and the receiver calculates the actual time that "makes sense" based on the delays of four sats as the signal passes through the atmosphere. Four equations with four unknowns and differential eq math gets you a 3d position.
TIL.