INTER-ANNUAL HEIGHT VARIATIONS OBSERVED BY GPS MEASUREMENTS IN TURKEY

We used the spherical harmonic function (SHF) and the local spherical symmetry (LSS) assumption methods to calculate the hourly and daily LEO satellite GPS differential code bias (DCB). The SHF method is more stable and precise than the LSS assumption. The daily DCB estimation is more accurate and stable than the hourly DCB due to more observation data. Hourly DCBs have large changes in one day, mainly be attributed to random errors because these error time series have a normal distribution.

We investigated the possible widening of the tropical belt along with the probable drivers and impacts based on high-accuracy, high-resolution GNSS RO data (2001–2020). The results show that the tropical belt has significant expansion in the Northern Hemisphere, while the Southern Hemisphere has no significant expansion.

In this paper, the receiver differential code bias (DCB) of BDS (BeiDou Navigation Satellite System) is estimated as the changing parameter within 1 d with epoch-by-epoch estimates. The intraday variability of receiver DCB is analyzed from 30 d of Multi-GNSS Experiment observations. In particular, the intraday stability of receiver DCB for the BDS-3 and BDS-2 observations is compared. The result shows that the intraday stability of BDS-3 receiver DCB is better than that of BDS-2 receiver DCB.

Atmospheric drag due to mass density distribution, particularly during storm-time, is of great importance for low Earth orbit precise orbit determination, and for the understanding of magnetosphere–ionosphere–thermosphere phenomena. In this paper, we investigate solar cycle, seasonal, and hemispheric asymmetry dependencies of thermospheric mass density disturbances due to magnetospheric forcing, from 10-year (2003–2013) continuous time series of GRACE estimates.