Lou Yidong, Huang Jinfang, Zhang Weixing, Liang Hong, Zheng Fu, Liu Jingnan
GNSS Research Center, Wuhan University, Wuhan 430079, China.
Collaborative Innovation Center of Geospatial Technology, Wuhan University, Wuhan 430079, China.
Sensors (Basel). 2017 Dec 27;18(1):65. doi: 10.3390/s18010065.
Tropospheric delay is one of the major factors affecting the accuracy of electromagnetic distance measurements. To provide wide-area real-time high precision zenith tropospheric delay (ZTD), the temporal and spatial variations of ZTD with altitude were analyzed on the bases of the latest meteorological reanalysis product (ERA-Interim) provided by the European Center for Medium-Range Weather Forecasts (ECMWF). An inverse scale height model at given locations taking latitude, longitude and day of year as inputs was then developed and used to convert real-time ZTD at GPS stations in Crustal Movement Observation Network of China (CMONOC) from station height to mean sea level (MSL). The real-time ZTD grid product (RtZTD) over China was then generated with a time interval of 5 min. Compared with ZTD estimated in post-processing mode, the bias and error RMS of ZTD at test GPS stations derived from RtZTD are 0.39 and 1.56 cm, which is significantly more accurate than commonly used empirical models. In addition, simulated real-time kinematic Precise Point Positioning (PPP) tests show that using RtZTD could accelerate the BDS-PPP convergence time by up to 32% and 65% in the horizontal and vertical components (set coordinate error thresholds to 0.4 m), respectively. For GPS-PPP, the convergence time using RtZTD can be accelerated by up to 29% in the vertical component (0.2 m).
对流层延迟是影响电磁距离测量精度的主要因素之一。为了提供广域实时高精度天顶对流层延迟（ZTD），基于欧洲中期天气预报中心（ECMWF）提供的最新气象再分析产品（ERA-Interim），分析了ZTD随海拔高度的时空变化。然后建立了一个以纬度、经度和一年中的日期为输入的给定位置的逆尺度高度模型，并用于将中国地壳运动观测网络（CMONOC）中GPS站的实时ZTD从站高转换为平均海平面（MSL）。随后生成了时间间隔为5分钟的中国实时ZTD网格产品（RtZTD）。与后处理模式下估计的ZTD相比，由RtZTD得出的测试GPS站ZTD的偏差和误差均方根分别为0.39厘米和1.56厘米，这比常用的经验模型精确得多。此外，模拟实时动态精密单点定位（PPP）测试表明，使用RtZTD在水平和垂直分量（设定坐标误差阈值为0.4米）中分别可将北斗PPP收敛时间加快多达32%和65%。对于GPS-PPP，在垂直分量（0.2米）中使用RtZTD可将收敛时间加快多达29%。
