Slant Tropospheric Delay Estimation Using the Integration of Operational Numerical Weather Modelling and CORS Observations

Lei Yang, Chris Hill, Chris Hide and Terry Moore

Abstract:	The effect of unmitigated tropospheric delay remains as one of the major error sources in the high accuracy positioning techniques, such as Precise Point Positioning (PPP). While the hydrostatic tropospheric delay can be well estimated to an accuracy of better than 5 mm (if surface pressure measurements are provided), the non-hydrostatic (or wet) delay is hard to model accurately due to the rapid spatial and temporal variation of the water vapour. In the traditional Slant Tropospheric Delay (STD) estimation methods, Zenith Tropospheric Delay (ZTD) is estimated first, then it is mapped on to individual satellite to receiver path. However both ZTD estimation and the mapping function have limited accuracy, especially when real time atmospheric profile information is not available. Besides, the mapping of the single zenith delay implies that the local atmosphere profile is symmetric around the receiver site, which does not valid in the event of weather front passing. In some severe cases, the azimuth dependent residue left on each STD will significantly deteriorate the PPP performance, in terms of both convergence time and height accuracy. In this study, a new approach to estimate the STD is proposed, which is based on two external resources: Numerical Weather Modelling (NWM) and observations from the local Continuously Operating Reference Stations (CORS) network. NWM could provide the STD estimation with real time information on the actual atmosphere, and the CORS observations could further enhance the temporal resolution of the NWM based STD estimation. Benefiting from these two extra inputs, applying the proposed tropospheric delay estimation could improve PPP positioning accuracy and efficiency, especially its convergence time. As both NWM and CORS observation can be available in real time, this study is aiming to propose an operational STD estimation solution. The algorithm of estimating STD using the integration of NWM and CORS observations is described, and preliminary test results are shown.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	3398 - 3405
Cite this article:	Yang, Lei, Hill, Chris, Hide, Chris, Moore, Terry, "Slant Tropospheric Delay Estimation Using the Integration of Operational Numerical Weather Modelling and CORS Observations," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 3398-3405.
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