基于垂直剖面函数式的全球对流层天顶延迟模型的建立

对流层延迟是无线电导航定位的主要误差源之一,其值对目标高程的变化敏感.在动态导航定位中,由于目标高程变化随机性强,延迟改正实时性需求高,已有的对流层延迟模型难以满足应用需求.本文利用2005到2006年ERA-Interim再分析气象资料积分方法计算的对流层天顶总延迟(ZTD)、天顶静力学延迟(ZHD)以及天顶非静力学延迟(ZWD)的垂直剖面研究了ZTD随高程变化的最佳拟合形式,并以此为基础建立了全球ZTD改正模型SHAO-H.该模型以大气中水汽的垂直分布规律为依据,将ZTD表示为高程的分段函数,进而再模制每段函数中各参数随时间的变化.精度评估显示:与积分ZTD相比,SHAO-H模型计算的ZTD在不同等压层上的平均bias大部分在±1 mm以内,随着高度的上升,平均RMS由39 mm减小至不足1 mm;与IGS (International GNSS Service)实测ZTD相比,SHAO-H模型的精度(bias为7.02 mm,RMS为38.50 mm)优于UNB3m模型(bias为14.67 mm, RMS为51.95 mm).SHAO-H模型具有精度稳定、计算简便等优点,适宜任意高度的用户使用.

Establishment of a new global model for zenith tropospheric delay based on functional expression for its vertical profile

The tropospheric delay is one of the most significant error sources for radio navigation and space geodetic techniques. Its value is seriously affected by the height of the observing object. Due to the requirement of real-time capability and the drastic variations in the height of the object, there are various defects in existing tropospheric delay models for calculating the delay in kinematic navigation and positioning. Based on the vertical profiles of zenith tropospheric delay (ZTD) derived from ERA-Interim reanalysis data in 2005 and 2006, as well as it's hydrostatic and non-hydrostatic components (ZHD and ZWD), the optimal fitting method of ZTD with respect to height was studied and a new global ZTD model which is referred to as SHAO-H was established. The SHAO-H model is built on the variation of water vapor in the vertical atmosphere and represents ZTD as a piecewise function of height. Then the variations of parameters in each function with respect to time are modeled. The most of mean bias between the SHAO-H ZTD and the integral ZTD at different isobaric layers are within ±1 mm, while the RMS reduces from 39 mm to less than 1 mm with the increase of height. Compared with International GNSS Service (IGS) ZTD at 117 global stations in 2011, the SHAO-H model (the bias is 7.02 mm, the RMS is 38.50 mm) is superior to the UNB3m model (the bias is 14.67 mm, the RMS is 51.95 mm). The SHAO-H model we constructed has many advantages such as consistency in accuracy and simplicity in computation, which is suitable for the users at arbitrary height in the neutral atmosphere.