So you tune in and hear "Hi there I'm a rogue air national guard F-16 flying at mach 2.0 precisely over the sears tower at 2000 ft ASL and headed due North at precisely noon"
Dude on the ground in .. Racine, lets say, hears that message and then a sonic boom a bit somewhat after noon.
So your math gets fed all that stuff, and then you draw a strangely shaped line on the map that predicts at that instant on your clock when you heard the sonic boom, that means you're standing on the ground somewhere along that peculiar shaped line. If you were being constantly overflown by rogue supersonic ANG F-16s from all different directions, your map would rapidly have one intersection point with a whole lot of lines drawn thru it, and thats where you are standing, at least relative to the sears tower, plus or minus your math ability.
But what if the broadcasting F-16 was just kidding about mach 2.0 and was actually chugging along at mach 1.9. Your line on the map is going to be all screwed up compared to where you actually are. Worst case isn't being 5% off and you laugh and discard the data, but every overflying rogue F-16 being a tiny little bit off, ruining your standard deviation and requiring a ton more samples be averaged together for the same accuracy.
The clock in your GPS is in fact disciplined to the clocks in the satellites, although its noise level is pretty bad (well, relatively, compared to the fancy clocks). If you've ever heard one of us RF guys talking and GPS Disciplined Oscillators or GPSDO that is exactly what we're talking about, an oscillator on the lab bench that is continuously aligned to be in perfect tune with the average GPS satellite, and this works shockingly well. For a couple hundred bucks your RF lab or ham radio station can have a "near atomic clock accuracy" reference clock for its oscillators, spectrum analyzers, freq counters, etc. Ham radio guys can get "hz" level accuracy at 10 GHz microwave freqs without much effort using this tech, for only a couple hundred bucks, which is pretty impressive and handy. All GPS rx have one of these, although performance and convenience vary. So the one in your phone doesn't have a convenient sma connector to feed 10 MHz refclock into my frequency counter... oh well, the innards are exactly the same. The innards of precision surveyor instruments are also lower noise and "better" than the innards of a phone. But the innards are functionally the same, more or less.
So you tune in and hear "Hi there I'm a rogue air national guard F-16 flying at mach 2.0 precisely over the sears tower at 2000 ft ASL and headed due North at precisely noon"
Dude on the ground in .. Racine, lets say, hears that message and then a sonic boom a bit somewhat after noon.
So your math gets fed all that stuff, and then you draw a strangely shaped line on the map that predicts at that instant on your clock when you heard the sonic boom, that means you're standing on the ground somewhere along that peculiar shaped line. If you were being constantly overflown by rogue supersonic ANG F-16s from all different directions, your map would rapidly have one intersection point with a whole lot of lines drawn thru it, and thats where you are standing, at least relative to the sears tower, plus or minus your math ability.
But what if the broadcasting F-16 was just kidding about mach 2.0 and was actually chugging along at mach 1.9. Your line on the map is going to be all screwed up compared to where you actually are. Worst case isn't being 5% off and you laugh and discard the data, but every overflying rogue F-16 being a tiny little bit off, ruining your standard deviation and requiring a ton more samples be averaged together for the same accuracy.
The clock in your GPS is in fact disciplined to the clocks in the satellites, although its noise level is pretty bad (well, relatively, compared to the fancy clocks). If you've ever heard one of us RF guys talking and GPS Disciplined Oscillators or GPSDO that is exactly what we're talking about, an oscillator on the lab bench that is continuously aligned to be in perfect tune with the average GPS satellite, and this works shockingly well. For a couple hundred bucks your RF lab or ham radio station can have a "near atomic clock accuracy" reference clock for its oscillators, spectrum analyzers, freq counters, etc. Ham radio guys can get "hz" level accuracy at 10 GHz microwave freqs without much effort using this tech, for only a couple hundred bucks, which is pretty impressive and handy. All GPS rx have one of these, although performance and convenience vary. So the one in your phone doesn't have a convenient sma connector to feed 10 MHz refclock into my frequency counter... oh well, the innards are exactly the same. The innards of precision surveyor instruments are also lower noise and "better" than the innards of a phone. But the innards are functionally the same, more or less.