## 1 Introduction
The magnitude of the multipath errors is related to the distance between the antenna and the object, the angle of the reflected signal, and the characteristics of the reflector [7]. The principle of SICB is similar, but the reflection occurs at the satellite ends. In order to mitigate or even eliminate the effects of SICB, a piecewise linear correction model for each frequency of BDS-2 IGSO-type and MEO-type satellites based on the trends of SICB against satellite elevation angles was proposed by [PERSON] and [PERSON] [5]. The SICB correction model was stable over time. After adding the correction values to the original code observations,the elevation-dependent SICB variations almost disappeared. Many researchers have focused on the refinement of this SICB correction model since then. To reduce the number of correction parameters, a correction model based on third-order polynomial fitting was developed by [PERSON] et al. [8]. The SICB correction values were produced together with their stochastic information by [PERSON] et al. [9], and the stochastic information can be used as precision indexes to refine the stochastic models of code measurements. According to [PERSON] et al. [10] and [PERSON] et al. [11], it was found that there existed obvious differences with respect to SICB variations against elevations for satellites with the same orbit type. Thus, they improved the correction model by estimating the correction values for each BDS-2 satellite, rather than IGSO-type or MEO-type satellites. All the above SICB correction models were established using the multipath (MP) combinations over all continuous ambiguity blocks. However, the MP combination inconsistency in terms of its absolute value, which is caused by the cycle slips and different tracking of a satellite at different stations, was ignored during the modeling process. In addition, the detailed SICB variations with elevation angles were vanished when using the piecewise linear fitting with a node separation of 5\({}^{\circ}\) or 10\({}^{\circ}\), or especially the polynomial fitting. Due to the negative effects of the above two flaws, the accuracy of the current SICB correction model needs to be further improved. The precise applications using the code measurements will be severely affected by the SICB. Many efforts have been made to investigate the benefits from SICB correction model. After applying the SICB correction values, an accuracy improvement of larger than 80% in the vertical direction could be achieved for the single-frequency precise point positioning (PPP) with BDS-2 IGSO and MEO satellites [12]. With the careful SICB consideration, the three-dimensional (3D) accuracy of overlapping orbits was improved from 11.0 and 14.0 cm to 6.9 and 10.5 cm for the BDS-2 MEO and IGSO satellites, respectively [13]. The precise correction of SICB resulted in a significant improvement of larger than 75% for wide-lane uncalibrated phase delay (UPD) estimation and a minor improvement of less than 25% for narrow-lane UPD estimation with respect to the PPP ambiguity resolution [14]. The long-term stability of differential code bias (DCB) for BDS-2 MEO satellites was improved by 12-28% after the SICB was corrected [15]. In this contribution, the single-frequency PPP is also used to verify our proposed SICB correction model. The code observations from BDS-2 GEO satellites also suffer from the SICB effects. Following [PERSON] et al. [8], the SICB variations of BDS-2 GEO satellites could be roughly corrected by the SICB correction model of BDS-2 IGSO satellites. However, the SICB correction for BDS-2 GEO satellites plays a limited role in improving the ambiguity-float PPP performance because the elevation angles  
Figure 1: Principle of multipath. of these satellites are almost constant. In addition, the code observations of BDS-2 GEO satellites are severely biased by ground multipath effects with an amplitude of 1-2 m, which are caused by ground-reflected satellite signals. [PERSON] et al.