School of Geodesy and Geomatics, Wuhan University, No. 129 Luoyu Road, Wuhan 430079, China.
GNSS Research Center, Wuhan University, No. 129 Luoyu Road, Wuhan 430079, China.
Sensors (Basel). 2018 Jul 3;18(7):2127. doi: 10.3390/s18072127.
Seasonal signals caused by the Earth’s surface mass redistribution can be detected by Global Navigation Satellite Systems (GNSS). The authors analyze the effect of Helmert transformation parameters and weight matrices, as well as the additional draconic signals on seasonal signals, in the GNSS coordinate time series. Moreover, the contribution of environmental loading models to the GNSS position series is assessed. Position time series of 647 global stations, with spans of 2⁻21 years are collected to generate six cumulative solutions using different parameters estimated in a deterministic model, as well as weight matrices. Comparison among the different solutions indicates that Helmert transformation parameters and weight matrices can result in a root mean square of 0.1 mm and 0.3 mm for seasonal signals, respectively. Compared to the displacements obtained from environmental loading models, seasonal signals estimated with the Helmert parameters and full weight matrices considered seems to have the best agreement with the results of the loading model. Meanwhile, the additional draconic signals are not effective to be parameterized in the deterministic model with an observation time span less than 15 years, marginally. There are 62%, 72% and 90% of 647 stations with weight root mean squares (WRMS) reduced by removing the loading-model-induced changes from the GNSS residual series for the east, north and vertical components, respectively. Finally, to obtain a velocity estimation with a bias of less than 0.1 mm/yr induced by seasonal signals, the position series with a time span greater than seven years is suggested.
地球表面质量重新分布引起的季节性信号可以通过全球导航卫星系统（GNSS）检测到。作者分析了 Helmert 变换参数和权矩阵以及额外的龙形信号对 GNSS 坐标时间序列中季节性信号的影响。此外，还评估了环境负荷模型对 GNSS 位置序列的贡献。收集了 647 个全球站的位置时间序列，跨度为 2⁻21 年，使用确定性模型中估计的不同参数和权矩阵生成了六个累积解。不同解之间的比较表明，Helmert 变换参数和权矩阵分别可以导致季节性信号的均方根误差为 0.1 毫米和 0.3 毫米。与环境负荷模型获得的位移相比，考虑 Helmert 参数和全权矩阵估计的季节性信号似乎与负荷模型的结果具有最佳的一致性。同时，在观测时间跨度小于 15 年的情况下，额外的龙形信号在确定性模型中进行参数化的效果并不明显。在 647 个站中有 62%、72%和 90%的站，在从 GNSS 残差序列中减去负荷模型引起的变化后，东、北和垂直分量的权均方根（WRMS）分别降低。最后，为了获得由季节性信号引起的偏差小于 0.1 毫米/年的速度估计，建议使用时间跨度大于七年的位置序列。
