# Mitigating the Scintillation Effect on GNSS Signals Using MP and ROTI
## 4 Discussion
During the scintillation period, 4 and 3 satellites were simultaneously affected by cycle slips at SJCU and SAOOP, respectively, and the numbers of visible satellite were 8 at both stations. This might indicate that more satellites affected by cycle slip could lead to the ineffectiveness of the weight strategy. To support this statement, the same investigation was conducted at SNA0P. During the scintillation period, the number of satellites affected by cycle slips were 5, 7 and 6 on 13 April 2016, 9 May 2016 and 6 June 2016, respectively, when the number of visible satellites were 11, 10 and 10, separately. In other words, 6, 3 and 4 satellites were free of cycle slip on the three days, respectively. Further, the improvement was obtained on 13 April 2016 but not on the other two days. This suggests that, when fewer satellites were affected by cycle slip, this could provide conditions for the successful application of the weight strategy. In addition, the elevation angles of satellites affected by cycle slip were investigated. On 7 September 2017, 8 September 2017 and 13 September 2017 at SAOOP and 7 September 2017 at SJCU, the satellite with the highest elevation angle was affected by cycle slips less than 4 times when that on 8 September 2017 and 13 September 2017 at SJCU was affected by cycle slips more than 8 times. A satellite with a higher elevation contributes more to the geometry quality of satellites. Thus, if the high-elevation satellite is less affected by cycle slips, the satellite geometry should also be less affected. Therefore, this suggests that it is more likely to obtain improvements with the weight strategy when the high-elevation satellite is less affected by cycle slips. Moreover, it was possible that standard parameters worked when scintillation parameters did not, and vice versa. Furthermore, it was also possible that either standard or scintillation parameters led to a higher improvement. One possible reason is that MP included in standard parameters is also able to characterize the multipath effect in addition to scintillation. Thus, standard parameters are capable of down-weighting more types of errors. On this occasion, standard parameters should be more effective in scintillation mitigation. However, MP and ROTI may sometimes fail to represent scintillation. In this case, scintillation parameters should be more effective in scintillation mitigation. Thus, standard parameters and scintillation parameters both have advantages in scintillation mitigation. As presented in the introduction section, a great deal of research has been conducted to improve positioning accuracy under the scintillation conditions. By weighting the least square stochastic (LSS) model, the height positioning accuracy was respectively improved by 21% and 38% by [PERSON] et al. [6] and [PERSON] et al. [8], and the 3D positioning accuracy was separately improved by up to 77.3% and 75% by [PERSON] et al. [9] and [PERSON] et al. [10]. In contrast, by weighting the KF model, the height and 3D error improvements, respectively, reached 93.1% and 86.1% in this paper, which were substantially higher as compared with the results obtained by [PERSON] et al. [9] and [PERSON] et al. [10]. Moreover, scintillation parameters were required in all these methods when standard parameters (MP and ROTI) with comparable performance were alternative in the method used in this paper, which meant that the data with the time interval of 30 s could also be used to mitigate the scintillation effects. This substantially increased the coverage of scintillation study with the assistance of global agencies such as IGS, which provides data from more than 500 permanent GNSS stations covering over 100 countries. Furthermore, [PERSON] et al. [13] integrated data from multiple constellations to improve the height and 3D error by 63% and 57%, respectively. This could be a part of future work, where the effectiveness of the observation removal and weight strategies could be investigated.