Barometric altimetry system as virtual constellation applied in CAPS

作     者：AI GuoXiang SHENG PeiXuan DU JinLin ZHENG YongGuang CAI XianDe WU HaiTao HU YongHui HUA Yu LI XiaoHui 

作者机构：National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China School of PhysicsPeking UniversityBeijing 100871China National Time Service CenterChinese Academy of SciencesXi’an 710600China 

出 版 物：《Science China(Physics,Mechanics & Astronomy)》 (中国科学：物理学、力学、天文学（英文版）)

年 卷 期：2009年第52卷第3期

页      面：376-383页

核心收录：

学科分类：08[工学] 081601[工学-大地测量学与测量工程] 0805[工学-材料科学与工程（可授工学、理学学位）] 0816[工学-测绘科学与技术] 0704[理学-天文学] 

基　　金：Supported by the National Basic Research Program of China (Grant No. 2007CB815500) the National High Technology Research and Development Program (Grant No. 2004AA105030) the Pilot Project of the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KGCX1-21) the National Natural Science Foundation of China (Grant No. 10453001) 

主　　题：CAPS system navigation and positioning barometric altimetry bound solution 

摘      要：This work describes the barometric altimetry as virtual constellation applied to the Chinese Area Positioning System (CAPS), which uses the transponders of communication satellites to transfer navigation messages to users. Barometric altimetry depends on the relationship of air pressure varying with altitude in the Earth’s atmosphere. Once the air pressure at a location is measured the site altitude can be found. This method is able to enhance and improve the availability of three-dimensional positioning. The difficulty is that the relation between barometric pressure and altitude is variable in different areas and under various weather conditions. Hence, in order to obtain higher accuracy, we need to acquire the real-time air pressure corresponding to an altimetric region’s reference height. On the other hand, the altimetry method will be applied to satellite navigation system, but the greatest difficulty lies in how to get the real-time air pressure value at the reference height in the broad areas overlaid by satellite navigation. We propose an innovational method to solve this problem. It is to collect the real-time air pressures and temperatures of the 1860 known-altitude weather observatories over China and around via satellite communication and to carry out time extrapolation forecast uniformly. To reduce data quantity, we first partition the data and encode them and then broadcast these information via navigation message to CAPS users’ receivers. Upon the interpolations being done in receivers, the reference air pressure and temperature at the receiver’s nearby place is derived. Lastly, combing with the receiver-observed real air pressure and temperature, the site’s altitude can be determined. The work is presented in the following aspects: the calculation principle, formulae, data collection, encoding, prediction, interpolation method, navigation message transmission together with errors causes and analyses. The advantages and shortcomings of the technique a