###### Abstract
Various GPS multipath mitigation studies have been conducted in the coordinate-domain and the observation-domain [22]. However, the BDS features heterogeneous constellation, and the constellation operating periods are complicated. Therefore, the BDS multipath mitigation method in the coordinate-domain will no longer be applicable, and the multipath mitigation can only be performed in the observation-domain. Based on the multipath correlation, the observation-domain multipath mitigation methods can be categorized into two groups: (1) Time-domain correlation-based. [PERSON] et al. [23] converted the double-difference residuals to the single-difference residuals based on the \"zero mean\" assumption and used the advanced sidereal filtering (ASF) method to effectively mitigate the multipath of the BDS-2 satellites. [PERSON] et al. [24] proposed the pre-processing single-difference residuals based on Kalman and Rauch-Tung-Striebel Smoother filters and mitigated the multipath by the ASF. However, mitigating the multipath based on time shift has restrictions, such as \"end effect\" and inconsistent observation time. (2) Spatial-domain correlation-based. [PERSON] et al. [25] applied the dual-antenna receiver with a common clock to establish the single-difference observation equations and constructed a multipath hemispherical map (MHM) using the correlation of GPS satellites spatial-domain multipath. The MHM was not limited by the time shift of each satellite orbit repeat time (ORT) and only needed to calculate the current satellite position to directly mitigate the multipath, which improved the efficiency and the positioning accuracy. [PERSON] et al. [26; 27] considered that the satellite tracks were not strictly repeated and proposed a trend surface analysis-based multipath hemispherical map that effectively mitigated the GPS multipath. Moreover, the correlation of satellite spatial-domain multipath has been applied in precision point positioning [28] and dynamic relative positioning [29] to mitigate the multipath. Although the single-difference residuals can conveniently establish a multipath model, the conventional receivers cannot eliminate the receiver clock error, which makes it challenging to make the single-difference observation equations. [PERSON] et al. [30] proposed the \"zero mean\" assumption that has been applied to GPS and BDS multipath mitigation based on SF [31; 32]. The \"zero mean\" assumption solved some influencing factors of modeling the double-difference residuals for multipath mitigation. tion. Therefore, the multipath spatial-domain correlation and the \"zero mean\" assumption are combined in this paper, and the SD-MHM method based on the single-difference residuals and MHM is proposed to mitigate the BDS-2/BDS-3 multipath that is suitable for the conventional receivers. The proposed method reconstructs the double-difference residuals into single-difference residuals and implements multipath mitigation on each BDS satellite. Real field data were used in the experiments and the results suggest that the proposed SD-MHM method outperforms other state-of-the-art methods in mitigating the multipath and improving the positioning accuracy. This paper is organized as follows. In Section 2, the specific steps of building a single-difference multipath model are described; moreover, the ASF and SD-MHM are introduced. The orbital repeat time of BDS satellite is displayed in Section 3. The experiments and results are analyzed in Section 4. A discussion is made in Section 5. Section 6 gives the conclusions.