## 4 Conclusions  
In this study, we discussed the effects of four methods, including NENE, BILI, BICU, and JUNK, for the percentage of convergence time, the average convergence time and the calculation time of single station of SF TIC2 PPP. The numerical results show that: (1) the percentage of the convergence time of the estimated parameters through the BILI method is the shortest in every condition; and, (2) in the static mode, when the RMS is less than 5 cm, only the percentage of the BILI method calculation exceeds 40%. While in the kinematic mode, when the RMS is less than 15 cm, only the BILI method is more than 60% and 40% in the horizontal and vertical component, respectively. Under the other identical thresholds of the RMS, the percentage of the convergence time of the estimated parameters through BILI method is higher than the other three methods; (3) in the static mode, the average convergence time of the estimated parameters through BILI method is reduced by at least 2.2% when compared to the other three methods and the maximum is shortened by 23.6%; while, in the kinematic mode, they are 1.9% and 16.6%, respectively; and, (4) for the average computation time of a station, the BILI method has 0.121 s more than the shortest calculation time in the static mode and 0.038 s in the kinematic mode. Therefore, we chose the BILI method for calculating the TEC at the required time when using the TIC2 or TIC3 calculation based on the GIM grid products. Figure 11: (**a**) FLRS station, (**b**) TRO1 station and (**c**) ZECK station SF PPP coordinate deviation RMS statistics in kinematic mode. In order to verify the different constraint methods, a total of 18,720 tests were performed with 78 stations. The experimental results revealed the following findings: (1) the TIC1 convergence time percentage is slightly higher than the TIC0 in each convergence time threshold, while the TIC2 is larger and the TIC3 is the largest. That is to say, the convergence can be accelerated under the constraint conditions; (2) as compared with TIC0 method, the average convergence time of the TIC1 method is shortened by at least 4.0% and, at most, 28.9% in static mode. The TIC2 method has a larger percentage of shortening, at least up to 16.6%, the maximum up to 88.4%. However, in the vertical component, the TIC1 method is larger than the TIC2 method at the 68% level. Compared with TIC0, the TIC3 method is shortened by 46.5% at least and 88.8% at most. Additionally TIC3 method is better than TIC1 method and TIC2 method. In kinematic mode, the percentage of time that is shortened after the constraint is less than in static mode. The average convergence time of the TIC1 method is at least 2.1% shorter than the TIC0 method, and the maximum is shortened by 11.7%. The TIC2 method has a larger percentage of shortening compared to the TIC1 method, with a minimum of 2.5% and a maximum of 73.9%. The TIC3 method is superior to the TIC1 method and the TIC2 method, with a minimum of 5.4% reduction and a maximum reduction of 74.5% as compared to TIC0; and, (3) through comparative analysis, it is concluded that, the final positioning error of TIC0, TIC1, TIC2 and TIC3 methods are basically the same, no method is better. After the above analysis and conclusions, under the constraints of atmospheric error products, convergence can be accelerated, and there is no impact on the final accuracy improvement. [PERSON], [PERSON], [PERSON] and [PERSON] conceived and designed the experiments; [PERSON] and [PERSON] performed the experiments and analyzed the data; [PERSON] drew pictures; [PERSON] and [PERSON] wrote the paper; all authors reviewed the paper. The research was supported by the Fundamental Research Funds for the Central Universities (grant number: 2018 BSCXC25), partially sponsored by Postgraduate Research & Practice Innovation Program of Jiangsu Province (grant number: KYCX18_1952). The authors thank the anonymous reviewer for their valuable comments. Thanks also go to IGS for data and GIM provision.