This paper is based on the AR products from CODE, GFZ, CNES, PRIDE Lab, and in-house AR products for the performance assessment of PPP-AR in terms of convergence time, time to first fix and positioning accuracy. The experiment uses seven-day observation data from 40 IGS stations in 2022 and precise products of each AR product. The results show that under the static solution mode with confidence level of 95%, five products have the most obvious improvement in positioning accuracy at the time of 1 h, which are 46.58%(3.4 cm), 41.10%(3.0 cm), 45.21%(3.3 cm), 34.25%(2.5 cm), and 41.10%(3.0 cm), respectively. In the simulation-kinematic solution mode, the positioning accuracy of the five products in the E and N directions can reach the millimeter level, and the accuracy of the U direction is slightly improved than that of the floating point solution, among which the accuracy of GBM product is the least improved, and 72.73%(2.4 cm), 47.37%(0.9 cm) and 5.41%(0.2 cm) were increased in E, N and U directions. WUM and COM products had better improvement effect. They were 81.82%(2.7 cm), 63.16%(1.2 cm), 24.32%(1.1 cm) and 81.82%(2.7 cm), 63.16%(1.2 cm), 15.58%(0.8 cm).

By analyzing the problems existing in the cycle slip detection method of wide-lane phase minus narrow-lane pseudorange and geometry-free combination, we propose a cycle slip detection method that considers the GNSS satellite elevation factor and is suitable for universal GNSS observation data. After detecting the epoch position where the cycle slip occurs, we use the method based on spatial search and minimum criterion of objective function to repair cycle slip. We then validate the proposed cycle slip processing method by selecting satellite data of different elevations observed from the universal GNSS receiver located at a landslide hazard near the Linxia Highway in Gansu Province. The results show that the proposed method is effective. the cycle slip detection and repair method can realize the accurate detection and repair of cycle slips in carrier phase data with different elevations and can reduce the influence of GNSS data observation error on the cycle slip test. It is feasible for the cycle slip detection and repair in universal GNSS observation data.

For the GPS modernization by adding L₅ frequency observable values, we propose a new algorithm of GPS single epoch double-difference integer ambiguity resolution called GPS Main and Auxiliary Frequency Correlation Algorithm (MAXCOM). We use only GPS single epoch data, including pseudo-range observation values and phase observation values of main-frequency and auxiliary-frequency for the algorithm. We set L₁ is set as the main-frequency and L₂ or L₅ as the auxiliary-frequency by expanding the idea of dual frequency correlation method to establish an internal-correlation model between double-difference phase observation values of GPS main-frequency and auxiliary-frequency. We conduct a cross-search between the adjustment value-domain of observation values and the value-domain of ambiguity, and then use the ratio significance test method to determine the double-difference integer ambiguity of GPS main-frequency. The example shows that for the three original phase observations of L₁, L₂ and L₅ frequency after GPS modernization, selecting L₅ as auxiliary-frequency of the algorithm is slightly better than L₂ in terms of efficiency and success-rate of ambiguity resolution. The proposed algorithm is effective.