Mendez Astudillo Jorge, Lau Lawrence, Tang Yu-Ting, Moore Terry
International Doctoral Innovation Centre, University of Nottingham Ningbo China, Ningbo 315100, China.
Department of Civil Engineering, University of Nottingham Ningbo China, Ningbo 315100, China.
Sensors (Basel). 2018 Feb 14;18(2):580. doi: 10.3390/s18020580.
As Global Navigation Satellite System (GNSS) signals travel through the troposphere, a tropospheric delay occurs due to a change in the refractive index of the medium. The Precise Point Positioning (PPP) technique can achieve centimeter/millimeter positioning accuracy with only one GNSS receiver. The Zenith Tropospheric Delay (ZTD) is estimated alongside with the position unknowns in PPP. Estimated ZTD can be very useful for meteorological applications, an example is the estimation of water vapor content in the atmosphere from the estimated ZTD. PPP is implemented with different algorithms and models in online services and software packages. In this study, a performance assessment with analysis of ZTD estimates from three PPP online services and three software packages is presented. The main contribution of this paper is to show the accuracy of ZTD estimation achievable in PPP. The analysis also provides the GNSS users and researchers the insight of the processing algorithm dependence and impact on PPP ZTD estimation. Observation data of eight whole days from a total of nine International GNSS Service (IGS) tracking stations spread in the northern hemisphere, the equatorial region and the southern hemisphere is used in this analysis. The PPP ZTD estimates are compared with the ZTD obtained from the IGS tropospheric product of the same days. The estimates of two of the three online PPP services show good agreement (<1 cm) with the IGS ZTD values at the northern and southern hemisphere stations. The results also show that the online PPP services perform better than the selected PPP software packages at all stations.
由于全球导航卫星系统（GNSS）信号在对流层中传播时，会因介质折射率的变化而产生对流层延迟。精密单点定位（PPP）技术仅使用一台GNSS接收机就能实现厘米/毫米级的定位精度。在PPP中，天顶对流层延迟（ZTD）与位置未知数一起进行估计。估计得到的ZTD对气象应用非常有用，例如根据估计得到的ZTD来估算大气中的水汽含量。PPP在在线服务和软件包中通过不同的算法和模型来实现。在本研究中，对来自三个PPP在线服务和三个软件包的ZTD估计值进行了性能评估并分析。本文的主要贡献在于展示了PPP中ZTD估计可达到的精度。该分析还为GNSS用户和研究人员提供了关于处理算法对PPP ZTD估计的依赖性和影响的见解。本分析使用了分布在北半球、赤道地区和南半球的九个国际GNSS服务（IGS）跟踪站的八整天观测数据。将PPP ZTD估计值与同一天从IGS对流层产品获得的ZTD进行比较。三个在线PPP服务中的两个服务的估计值在北半球和南半球站与IGS ZTD值显示出良好的一致性（<1厘米）。结果还表明，在所有站点，在线PPP服务的性能均优于所选的PPP软件包。
