Comparison of GPS Loss of Lock with S4-proxy from IGS network data and S4 from SCINDA network data over Bahir Dar

This paper compares the occurrence of GPS Loss of Lock events from IGS network data to defined values of both the Amplitude scintillation index (S4) from a dedicated scintillation receiver of SCINDA network and the Amplitude scintillation proxy (S4-proxy) from IGS network data measurements in Bahir Dar. LOL may occur at any level of S4 due to other dominating factors; however, in our case studies, the threshold values of both S4 and S4-proxy are greater or equal to 0.7, which is more responsible for the occurrence of LOL. Most of Loss-of-Lock events occurred when both S4 and S4-proxy were greater than or equal to 0.7, implying that LOL occurrence increases with the severity of scintillation and peaks for strong ionospheric scintillation, implying that low S4 and S4-proxy values were associated with infrequent Loss of Lock, whereas high values were usually associated with Loss-of-Lock. According to our findings, there were no Loss-of-Lock events in the absence of strong scintillation operation (S4 and S4-proxy > 0.7). Ionospheric Scintillation never simultaneously occurred on all PRN signals to impact all satellites in the field of view of a receiver simultaneously, however only strong scintillation events S4 > 0.7 and S4-proxy > 0.7 values are causes of Loss-of-Lock. Loss-of-Lock events and strong S4 and S4-proxy values only occurred in the same region of the sky(North-West region) and during the same time, according to our observations. This implies that S4,S4-proxy and Loss-of-Lock are correlated in terms of temporal and azimuth distribution. The absence of geomagnetic storms on the days on which LOL were observed, rules out the likelihood that the occurrence of LOL at equatorial regions is linked to geomagnetic storms. As a result, we discovered that strong ionospheric scintillation is a dominant cause of Loss-of-Lock events in the equatorial region, such as Bahir Dar. Finally, these findings suggest that ionospheric scintillation indices derived from IGS network data, such as S4-proxy values, are equally responsible for determining whether a Loss-of-Lock event is likely to occur and are appropriate for studying ionospheric scintillation in the regions where there are no dedicated scintillation receivers of the SCINDA network.