GPS连续观测站的噪声分析

ANALYSIS ON THE NOISES FROM CONTINUOUSLY MONITORING GPS SITES

分析了中国地壳运动观测网络在全国布设的27个GPS连续站开始运行以来至2005年11月的站坐标时间序列.在对数据进行清理的基础上,分析了各站坐标分量噪声的功率谱密度,计算了表征各分量的噪声特性的谱指数.谱指数显示,大部分站的各坐标分量时间序列的噪声可以用白噪声+闪烁噪声的模型来描述,少部分则可用白噪声+闪烁噪声+随机漫步噪声的模型来描述.采用最大似然估计准则,定量估计了模型中的各噪声分量.结果表明,GPS站坐标时间序列中白噪声甚至不是噪声的主要成分.因此,仅顾及白噪声得到的测站运动参数的误差估计,实际上是过高的,或者说是过于乐观的.相应地,对这些运动参数作出解释时,如果不充分考虑这一因素,有可能会对读者产生误导.

In this paper, we analyze the time series of site coordinates of 27 continuously monitoring GPS sites covered by the Crustal Movement Observation Network of China over the whole country. The data are obtained in the period from the beginning of the observation to the November of 2005. On the basis of data processing, we analyze the power spectrum density of coordinate component noise at each site and calculate the spectral indexes manifesting the noise property of each component. The spectral indexes indicate that for most sites, the noise of time series of each coordinate component can be addressed by the model of white noise -I- flicker noise; and for a small amount of sites, it can be de- scribed by the model of white noise ＋ flicker noise ＋ random walk noise. We also quantitatively estimate each noise component in the model by using the criterion of maximum likelihood estimation. The result shows that the white noise in the time series of GPS site coordinates does not constitute the main part of noise. Therefore, the error estimation of site movement parameters is usually too small, or too optimistic if we consider the white noise only. Correspondingly, if this factor is not fully considered in explaining these movement parameters, it might mislead the readers.