Computational and geometrical aspects of on-the-fly ambiguity resolution
Abstract
Precise (centimetre level accuracy) kinematic differential positioning using GPS (Global Positioning System) requires the use of carrier phase observations with correctly resolved integer ambiguities. On-the-fly ambiguity resolution, i.e., ambiguity resolution while the receiver is in motion, is desirable, since it increases the flexibility and reliability of kinematic positioning. On-the-fly ambiguity resolution, however, is not an easy task. A lot of factors can be categorized into three broader groups, namely the ambiguity resolution technique, the effects of the observation errors and biases, and the observation geometry, i.e.., the geometry between the satellites, the monitor station(s), and the user.
In this research, the possibility of performing reliable and fast on-the-fly ambiguity resolution of GPS carrier phase signals is studied. An integrated on-the-fly ambiguity resolution technique was developed for this research. This technique was designed to work with either single-frequency, codeless, or dual-frequency GPS data from a minimum of five observed satellites, and it accommodates the use of more than one monitor station. The validity of the technique has been verified using static, simulated kinematic, and kinematic GPS data. The technique has been shown to be capable of resolving initial integer ambiguities on-the-fly reliable and quickly, even instantaneously under certain conditions.
Geometrical and computational aspects of on-the-fly ambiguity resolution have also been studied in this research, particularly related to their effects on the performance of on-the-fly ambiguity resolution. The geometrical aspects studied involve the following geometrical parameters: the wavelength of the signal, selection of primary satellites, number of satellites, observation differencing strategy, location of satellites available, data rate, number of secondary monitor stations, and location of secondary monitor stations. The computational aspects studied involve the ambiguity searching space construction and the process of identifying the correct ambiguities.