A Theoretical and Empirical Integrated Method to Select the Optimal Combined Signals for Geometry-Free and Geometry-Based Three-Carrier Ambiguity Resolution

Abstract

Twelve GPS Block IIF satellites, out of the current constellation, can transmit on three-frequency signals (L1, L2, L5). Taking advantages of these signals, Three-Carrier Ambiguity Resolution (TCAR) is expected to bring much benefit for ambiguity resolution. One of the research areas is to find the optimal combined signals for a better ambiguity resolution in geometry-free (GF) and geometry-based (GB) mode. However, the existing researches select the signals through either pure theoretical analysis or testing with simulated data, which might be biased as the real observation condition could be different from theoretical prediction or simulation. In this paper, we propose a theoretical and empirical integrated method, which first selects the possible optimal combined signals in theory and then refines these signals with real triple-frequency GPS data, observed at eleven baselines of different lengths. An interpolation technique is also adopted in order to show changes of the AR performance with the increase in baseline length. The results show that the AR success rate can be improved by 3% in GF mode and 8% in GB mode at certain intervals of the baseline length. Therefore, the TCAR can perform better by adopting the combined signals proposed in this paper when the baseline meets the length condition.

Cycle Slip Detection during High Ionospheric Activities Based on Combined Triple-Frequency GNSS Signals

“…With the development of GNSS, the availability of triple-frequency signal provides new opportunities for cycle slip detection under high ionospheric activities by introducing additional combined signals with longer wavelengths, weaker ionospheric delays and smaller measurement noise [22,23]. Zhao et al [24] tried to detect cycle slips under high ionospheric activities by predicting the ionospheric delay based on the assumption that ionospheric delay remains unchanged within a period.…”

“…where denotes the time differenced operation between two consecutive epochs; N is the ambiguity; the subscripts indicate the frequencies; (i, j, k) indicates the combined signal with the coefficients i, j and k for the frequencies [23]; λ is the wavelength; P and Φ represent the code measurement and the phase measurement in units of length respectively;Φ (0,1,−1) is the combined phase measurement (0, 1, −1) where cycle slips have been corrected; a, b, c and d are the coefficients. Compared to the traditional HMW combination, this modified HMW combination can have a better manipulation of the ionospheric bias and measurement noise [13].…”

Triple-Frequency Code-Phase Combination Determination: A Comparison with the Hatch-Melbourne-Wübbena Combination Using BDS Signals

“…No BDS data are validated [8,26,27] (1) Mixed code-phase combinations (2) Fix ambiguity by rounding WL ambiguity fixing relies on the resolved EWL ambiguity [3,28] (1) Mixed code-phase combinations (2) Fix ambiguity by rounding no specific discussion of the code coefficients in the combination…”

“…Deo et al [25] gives the triple-frequency ionosphere-free combinations for code and phase observations separately, but only the dual-frequency signals were used in the mixed code-phase combinations. Zhao et al [26] introduced different criteria to select the optimal combined signals for GF and geometry-based (GB) TCAR, respectively. For GF TCAR the sum of the ionosphere scale factor (ISF), the measurement noise, the wavelength to total noise ratio, and the success rate are all considered, and the coefficients of the code combination in code-EWL and code-WL signal pairs were restricted to be integer numbers but, in fact, this is needless.…”

Extra-Wide Lane Ambiguity Resolution and Validation for a Single Epoch Based on the Triple-Frequency BeiDou Navigation Satellite System

“…The approach starts with the easy-to-fix, extra-wide lane (EWL) combination and steps to the shorter wavelength wide-lane (WL) and narrow-lane (NL) combinations sequentially, whereby the WL combination is used to bridge the longest wavelength EWL and the shortest wavelength NL. Following on from these studies, a large amount of work has been carried out on triple-frequency ambiguity resolution using the TCAR/CIR or modified TCAR/CIR methods [12][13][14][15].…”