[aprssig] How gps works

[Andrew Rich]

Hello

I am learning how gps works

I understand that gps satellites contain accurate clocks

How does the receiver know the distance to the bird ? 

Does it look at the pattern coming from the gps sat ?

Can it work out when comparing the code from others sats to know the difference in time between the different birds, much like trying to line up a set of rulers ?

What does sending empheris data do to help ? Does that help the receiver picture the constellation ? 

From what I can gather, the time is very critical and to know how long signals take to travel , I see the need for all sats to send the same pattern and in time with each other ?

Also gravity affects time. Time travels faster in less gravity . I know they have to correct this .

All I need to work out is the distance to bird mechanism

Sent from my iPhone
Andrew Rich