Panetier Aurélie, Bosser Pierre, Khenchaf Ali
PIM UMR 6285 CNRS, Lab-STICC (Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance), ENSTA Bretagne, 29200 Brest, France.
M3 UMR 6285 CNRS, Lab-STICC (Laboratoire des sciences et techniques de l'information, de la communication et de la connaissance), ENSTA Bretagne, 29200 Brest, France.
Sensors (Basel). 2023 Jul 22;23(14):6605. doi: 10.3390/s23146605.
The atmospheric water vapor is commonly monitored from ground Global Navigation Satellite System (GNSS) measurements, by retrieving the tropospheric delay under the Zenith Wet Delay (ZWD) component, linked to the water vapor content in the atmosphere. In recent years, the GNSS ZWD retrieval has been performed on shipborne antennas to gather more atmospheric data above the oceans for climatology and meteorology study purposes. However, when analyzing GNSS data acquired by a moving antenna, it is more complex to decorrelate the height of the antenna and the ZWD during the Precise Point Positioning (PPP) processing. Therefore, the observation modeling and processing parametrization must be tuned. This study addresses the impact of modeling on the estimation of height and ZWD from the simulation of shipborne GNSS measurements. The GNSS simulation is based on an authors-designed simulator presented in this article. We tested different processing models (elevation cut-off angle, elevation weighting function, and random walk of ZWD) and simulation configurations (the constellations used, the sampling of measurements, the location of the antenna, etc.). According to our results, we recommend processing shipborne GNSS measurements with 3° of cut-off angle, elevation weighting function square root of sine, and an average of 5 mm·h-1/2 of random walk on ZWD, the latter being specifically adapted to mid-latitudes but which could be extended to other areas. This processing modeling will be applied in further studies to monitor the distribution of water vapor above the oceans from systematic analysis of shipborne GNSS measurements.
大气中的水汽通常通过地面全球导航卫星系统（GNSS）测量来监测，即通过反演天顶湿延迟（ZWD）分量下的对流层延迟来实现，该延迟与大气中的水汽含量相关。近年来，已在船载天线上进行GNSS ZWD反演，以获取更多海洋上空的大气数据用于气候学和气象学研究。然而，在分析移动天线获取的GNSS数据时，在精密单点定位（PPP）处理过程中，使天线高度和ZWD去相关更为复杂。因此，必须调整观测建模和处理参数化。本研究通过船载GNSS测量模拟，探讨建模对高度和ZWD估计的影响。GNSS模拟基于本文作者设计的模拟器。我们测试了不同的处理模型（仰角截止角、仰角加权函数和ZWD的随机游走）和模拟配置（使用的星座、测量采样、天线位置等）。根据我们的结果，我们建议处理船载GNSS测量时采用3°的截止角、正弦平方根的仰角加权函数以及ZWD上平均5 mm·h-1/2的随机游走，后者特别适用于中纬度地区，但也可扩展到其他地区。这种处理建模将应用于进一步的研究中，通过对船载GNSS测量的系统分析来监测海洋上空水汽的分布。
