Precise Relative Positioning Using Doppler Measurements of Android Smartphones

Android provided raw satellite measurements; however, the limitations of the GNSS function of smartphones results in causing large multipath errors and unstable carrier phase measurement. This makes it difficult to apply full real-time kinematic positioning. Furthermore, the provision of carrier measurements via different manufacturers is not well-performed. So, this paper proposes the code-Doppler smoothing method. The technique did not receive attention in studies based on high-performance receivers where carrier measurements could be received seamlessly. Doppler measurements are less accurate than carrier measurements, but they are more accurate than code measurements and free from cycle slips. Using the technique, it is expected that a smartphone can be used as a personal navigation system with a simple process. In fields such as formation flight where the separation between vehicles is important, obtaining the baseline vector between two vehicles by one process is more efficient than using the positions of each vehicle. When determining the baseline vector, differencing the pseudorange of two receivers that are in proximity to each other helps remove common errors. Determining the baseline vector using this approach is known as relative positioning, which is efficient and accurate. This paper uses Android smartphones for relative positioning with code-Doppler Smoothing method to obtain baseline vectors between vehicles. The efficiency and accuracy of the proposed method was evaluated under static and dynamic conditions in a routine experimental environment. High-, intermediate-, and low-grade receivers were used to verify the system performance, and the positioning error RMS has decreased up to 60%.