The data portion of the GIM products utilized contain a total of 25 maps, with the latitude variation ranging from 87.5\({}^{\circ}\) to \(-\)87.5\({}^{\circ}\) with an interval \(-\)2.5\({}^{\circ}\) and the longitude ranging from \(-\)180\({}^{\circ}\) to 180\({}^{\circ}\) at 5\({}^{\circ}\) intervals. The accuracy of the GIM is improved based on the Spherical Harmonic (SH) expansion model [17]. The VTEC of each ionospheric grid point is obtained while using different interpolation methods, such as bilinear interpolation [18], inverse distance weighted function [19], and Kriging interpolation [20]. [PERSON] and [PERSON] [21] proposed a polynomial model for single-station TEC derivation, and a single-station receiver bias can be estimated while using this model [22]. This method was used by [PERSON] et al. [23] to study the effects of ionospheric shell height on GPS-based TEC derivation by a single station, while [PERSON] et al. [24] applied this method to multi-stations. [PERSON] et al. [25] analyzed the applicability of the sophisticated Klobuchar model for VTEC in China. [PERSON] et al. [26] had based on GPS to observe and analyze the fluctuation characteristics of TEC over China. In GNSS data processing, the slant tropospheric delay on the signal propagation path between the satellite and the receiver is usually mapped to the zenith direction via a mapping function. The Zenith Tropospheric Delay (ZTD) consists of the Zenith Hydrostatic Delay (ZHD) and the Zenith Wet Delay (ZWD, i.e., the zenith non-hydrostatic delay). The models of tropospheric delay estimation usually adopt the Hopfield model and Saastamoinen model. There are roughly two types of mapping functions. The first type are empirical models, which merely require the epoch time and the approximate coordinates of the receiver station, such as the Niell Mapping Function (NMF) [27] and the Global Mapping Function (GMF) [28]. The second type of mapping function is based on a large number of weather model analyses at the epoch of the observations, such as Isobaric Mapping Functions (IMF) [29] and Vienna Mapping Functions (VMF1) [28]. [PERSON] et al. [30] proposes a new Asian single site tropospheric correction model, called the Single Site Improved European Geostationary Navigation Overlay Service model (SSIEGNOS). SF PPP cannot be combined or differenced to be eliminated or attenuated by a part of the error, like dual-frequency PPP. If there are some information related to the parameters, and this information is accurate enough, the precision of traditional SF PPP can be largely improved and the convergence time can be shortened. [PERSON] et al. [31] studied real-time GIM and its application in SF positioning, [PERSON] and [PERSON] [32] studied the effect of atmospheric-constrained on the convergence time of dual- and triple-frequency PPP, and [PERSON] et al. [33] applied the Inertial Navigation System (INS) to the ionosphere-constrained PPP to overcome the drawbacks that accompany unexpected and unavoidable substandard observation environments. This study uses the GIM products and the tropospheric zenith path delays from the IGS as the constrained information for SF PPP. The organization of this study is as follows: the next step details the methods for mathematical models of standard SF GPS PPP, troposphere-constrained SF GPS PPP, and the details of the four interpolation methods of GIM products. Afterwards, in Section 3 we compare and analysis the influence of interpolation methods and constraint methods on SF GPS PPP convergence time, and finally in Section 4 we draw conclusions. Later, we will study ionospheric delay and tropospheric delay prediction models to provide virtual atmospheric delay observations for real-time PPP and also provide a priori information for the constraint processing.