# A Novel Error Correction Approach to Improve Standard Point Positioning of Integrated BDS/GPS
## 1 Introduction  
Over the past few years, satellite navigation technology has achieved rapid development, but there are still some problems to be solved in some aspects. For example, in terms of reliability and integrity, a single navigation system is difficult to meet the requirements of positioning accuracy in some areas with complex terrain due to insufficient visible satellites [1]. In addition, in some applications with high dynamic requirements, the dynamic positioning of satellite navigation is not good enough to meet the needs of practical applications. Therefore, to improve navigation positioning accuracy and performance, the integration of GPS and BDS can be used, which will increase the number of visible stars; enhance the quality of observation; reduce the spatial position accuracy factor; improve the integrity, reliability and stability of the satellite navigation system; improve the ability of satellite navigation system positioning services and the positioning accuracy of the integrated positioning system; and expand the application field of satellite navigation [2]. Many methods can be used to achieve the positioning of integrated BDS/GPS, such as real-time kinematic (RTK), precision point positioning (PPP) and SPP. RTK is a technique that uses the carrierphase in the satellite signal as the observation and uses the difference equation to solve the ambiguity to achieve the dynamic positioning between the mobile station and the reference station [3]. At present, the static positioning accuracy of RTK technology can reach even centimeters or even millimeters [4]. However, due to the dependence of RTK technology on carrier signals, it is susceptible to signal spoofing, interference and occlusion. PPP is a solution to solving the position using precise ephemeris, precise satellite orbit and precision satellite clock and dual-frequency carrier phase observations [5; 6]. It can be divided into non-differential PPP and differential PPP according to the data processing [7; 8; 9]. The current PPP positioning accuracy can reach decimeter or even centimeter level [10]. However, the shortcoming of PPP is that the initialization time and re-initialization time after the satellite loses lock is very long, and the precision ephemeris can only be processed afterwards, so its scope of use is limited. SPP is a technique for determining the absolute coordinates of the receiver in Earth's coordinate system based on satellite broadcast ephemeris and observations from a single receiver [11; 12]. Due to the above shortcomings of RTK and PPP, if the positioning accuracy of SPP can be improved, it would be more suitable for use in vehicle applications. There are many error sources in the positioning process [13; 14; 15]. In the positioning process, various errors are roughly divided into the following three aspects according to different sources: (a) Satellite-related errors, which mainly include satellite clock errors and ephemeris errors, are due to the fact that they are affected by various complex factors, making it difficult to accurately match the operational model to the correction model and orbital parameters. (b) There are errors related to signal propagation. The influence of various substances in the atmosphere that satellite signals must pass through the atmosphere is called atmospheric delay. Atmospheric delays generally include ionospheric delays and tropospheric delays. (c) Receiver-related errors mainly include multi-path effects, electromagnetic interference, receiver noise, and software calculation errors. To achieve precise positioning, a correction model of the positioning error must be established to correct the positioning accuracy and minimize the effects of errors. Different methods have been proposed by many researchers to reduce positioning errors. [PERSON] et al. proposed a wavelet packet algorithm based on two-dimensional moving weighted average processing (WP-TD) for extracting multipath [16]. [PERSON] et al.