**6. GPS measurements**

While tracking a satellite signal, a GPS receiver monitors three parameters: pseudoranges, carrier phase, and Doppler [7, 11]. A pseudorange is calculated by measuring the signal transit time from a satellite to the receiver and is described as "pseudo" ranges because these measurements are corrupted by satellite and receiver clock biases [6]. Carrier phase measurements track the difference between the carrier phases for the received and a locally generated replica of the signal. The Doppler measurement reflects the rate of change of the carrier phase [12].
