[time-nuts] What position is measured?

jimlux jimlux at earthlink.net
Tue Sep 7 13:30:22 UTC 2010


Peter Krengel wrote:
> Hi nuts,
> 
> have got some interesting question from friends.
> They asked 
> 
> What coordinates are measured and registrated by a GPS.
> Is it the position of the antenna, it could be 100m (300ft) away from me
> or is it the position of the GPS RX as this is the position of the µC where
> signals are processed?

Where the antenna is..

> 
> I answered, its allways the antenna position as there is the point where
> wave fronts coming in from the sats becomes electrical signals (note we are
> not talking about PPS but coordinates)...

Pretty good..
Another analogy is that if you had a machine that recorded all the 
signals, mounted right at the antenna, and then carried the recording 
half way around the world, and then ran the recording into a receiver, 
it would give you the position of the antenna, not the receiver.  The 
cable is just a time delay.


> 
> What do you think?
> 
> Peter, DG4EK
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