5.1 Observables

Four basic observables:

• The pseudoranges from code measurements: the time shift that is necessary to correlate the incoming code sequence with a code sequence generated in the GPS receiver, multiplied by the velocity of light:

  

  being the code (C/A) observed of the satellite j from receiver i, and its corresponding positions and , its corresponding clock errors.

• The pseudorange differences: the frequency shift of the received carrier is measured with respect to the reference frequency within the receiver (Doppler count or integrated Doppler measurement):

  

• The carrier phase, from a phase comparison between the received Doppler-shifted carrier signal and the receiver-generated reference frequency :

  

• Differences in signal travel time from interferometric measurements

• Different combinations of observations (Laboratory sessions)...
• Single, Double and Triple differences...