Study Of Ionospheric Delay Correction Based On GNSS Observations

As an important part of the Earth’s space environment, ionosphere has a seriously effecton the normal transmission of radio navigation signals，especially for the single-frequencynavigation users. It has been one of the most complicated and thorniest error sources in GNSS(Global Navigation Satellite Systems) positioning. The global ionospheric delay model can beestablished based on ground-based GNSS observations, in order to correct ionospheric delayeffectively. In addition, the satellite and receiver DCB parameters can be achieved accuratelythrough ionospheric delay model, providing services for precise positioning. At present gpsobservations are adopted to establish ionosphere model through post-processing ininternational measures, researching lillte in real-time ionospheric products. Since offeringofficial service in July2012, the donation for area navigation and positioning services of BDSnavigation system has completed. Considering the compatibility and interoperability indifferent navigation systems, it is necessary to research ionosphere correction products ofBDS system, to provide technical support for high-precision navigation and positioningservice. Based on the above, this paper carried out a study to establish global ionosphericdelay model based on GNSS observations, and on the basis, a research based on the sphericalcap harmonic function to achieve the real-tine regional ionospheric correction in China iscarried out. Additionally, considering the less observation stations and can not be modeledseparately of BDS system, a global ionospheric model is established based on GPS/BDSobservations, and DCB parameters of BDS satellite is achieved precisely. The main contentsof this paper can be summarized as follows:1. The principle, data processing method and parameter estimation strategy ofestablishing global ionospheric model by spherical harmonics based on GPS observations isanalyzed and concluded.2. The global ionospheric TEC grid model using GPS observations is realized. Andsatellite and receiver hardware delay bias is estimated accurately. Experimental analysisshows that the accuracy of ionosphere and DCB products achieved by this method is quite thesame as IGS products; 3. Establishing global Ionospheric model based on GPS/BDS observations andestimating BDS satellites and receivers DCB parameters accurately. Through experiment inBDS single frequency point positioning, results shows that the accuracy and validity of BDSionosphere and DCB products reliable.4. The regional Ionospheric model is established using Spherical Cap harmonicfunction and data from crustal movement monitoring network of China. And based on theseanalyses, a real-time Ionospheric delay correction method is realized and the accuracy andreliability of the real-time ionospheric products is analyzed.