A method of undifferenced ambiguity resolution for GPS+GLONASS precise point positioning

Abstract

Integer ambiguity resolution is critical for achieving positions of high precision and for shortening the convergence time of precise point positioning (PPP). However, GLONASS adopts the signal processing technology of frequency division multiple access and results in inter-frequency code biases (IFCBs), which are currently difficult to correct. This bias makes the methods proposed for GPS ambiguity fixing unsuitable for GLONASS. To realize undifferenced GLONASS ambiguity fixing, we propose an undifferenced ambiguity resolution method for GPS+GLONASS PPP, which considers the IFCBs estimation. The experimental result demonstrates that the success rate of GLONASS ambiguity fixing can reach 75% through the proposed method. Compared with the ambiguity float solutions, the positioning accuracies of ambiguity-fixed solutions of GLONASS-only PPP are increased by 12.2%, 20.9%, and 10.3%, and that of the GPS+GLONASS PPP by 13.0%, 35.2%, and 14.1% in the North, East and Up directions, respectively.

Characteristics of BeiDou Navigation Satellite System (BDS) Code Observations for Different Receiver Types and Their Influence on Wide-Lane Ambiguity Resolution

“…Firstly the true ambiguities were obtained by rounding the averaged float value of every continual data arcs of each pair of satellites [ 16 ]. Then, given a threshold of 0.25 [ 27 , 28 ], the WL ambiguity fixing rate is the result of dividing the number of fixed ambiguities by the number of ambiguities.…”

Improved Method for GLONASS Long Baseline Ambiguity Resolution without Inter-Frequency Code Bias Calibration

“…However, this method requires a precise ionospheric model to correct the ionospheric delay. Yi et al (2016) [40] calibrated the odd cycle in the HMW combination for GLONASS wide-lane ambiguity fixing, and found that 96.9% of the GLONASS wide-lane ambiguities can be fixed with a rounding criterion of 0.25 cycles. Liu et al (2018) [41] then calibrated the P1 and P2 IFCBs for GLONASS wide-lane ambiguity fixing and achieved comparable fixing percentages for homogenous and heterogeneous receivers.…”

“…Liu et al (2018) [41] then calibrated the P1 and P2 IFCBs for GLONASS wide-lane ambiguity fixing and achieved comparable fixing percentages for homogenous and heterogeneous receivers. While the methods proposed by Yi et al (2016) and Liu et al (2018) can perform GLONASS wide-lane ambiguity fixing directly using the traditional HWM combination, an IFCB calibration table must be established for each individual receiver, which will require considerable calibration work.…”