The Establishment and Precision Analysis of Global Ionospheric Model of COMPASS System
Ionospheric delay is one of the main error sources affecting the positioning and timing precision of satellite navigation system for single frequency users. China’s regional satellite navigation system uses ionospheric puncture point data of monitoring st
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The Establishment and Precision Analysis of Global Ionospheric Model of COMPASS System Xiuqiang Gong, Nan Xing, Shanshi Zhou, Yueling Cao, Xiaogong Hu and Bin Wu
Abstract Ionospheric delay is one of the main error sources affecting the positioning and timing precision of satellite navigation system for single frequency users. China’s regional satellite navigation system uses ionospheric puncture point data of monitoring stations to fit the 8 parameters of klobuchar model in geographic coordinate system,and broadcasts them to users through the navigation message which is valid for 2 h. Long-term monitoring shows that this model can correct the ionospheric delay up to 74 % in service area around China. Due to the lack of ionospheric measured data in the southern hemisphere and high latitudes of the northern hemisphere, this model can not guarantee the correction accuracy in equatorial belt and high latitudes. This paper improves the klobuchar model expressed in the form of 9 parameters. Not only this model can keep the ionospheric double-peak characteristic but also ensure global fitting precision. In order to obtain real-time ionospheric data outside regional monitoring network, this paper examines the precision of forecasting model based on ionosphere spherical harmonic coefficient. According to the results of comparison,the model in this paper can correct the ionospheric delay for the next 24 h up to 72 % in China. Globally, the correction accuracy reaches 70 % in the north hemisphere, while 69 % in the south hemisphere. As a result, the correction precision of the model is better than the model broadcasted by GPS.
Keywords COMPASS Ionosphere harmonics Magnetic symmetry
Klobuchar
Amplitude
Spherical
X. Gong (&) N. Xing S. Zhou Y. Cao XiaogongHu B. Wu Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China e-mail: [email protected]
J. Sun et al. (eds.), China Satellite Navigation Conference (CSNC) 2013 Proceedings, Lecture Notes in Electrical Engineering 245, DOI: 10.1007/978-3-642-37407-4_23, Ó Springer-Verlag Berlin Heidelberg 2013
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23.1 Introduction Ionosphere is usually instable and described by some empirical models, such as klobuchar, IRI and NeQuick, etc. IRI [1] model is built on large number of ionospheric sounding data, integration of multiple atmospheric modes and introduction of solar activity parameters and geomagnetic activity index. NeQuick model is based on the DGR profile proposed by Di Giovanni [2] and Radicella [2], and now it serves for Galileo’s single frequency users after modification and optimization. IRI and NeQuick model can both describe the three-dimensional ionospheric image, simulate the ionosphere’s double-peak structure [3] located on both sides of the equator. However, klobuchar model considers all of the free electrons concentrated on one spherical surface about 350–450 km height. Klobuchar model is especially suitable for mid-latitude zone. It is adopted for GPS and the precision is lower tha
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