Mitigation of atmospheric effects on GNSS

自1993年以来，已有24颗或更多的GPS卫星提供了全球覆盖和定位能力。不久的将来将对全球定位系统进行改进，欧洲的卫星导航系统伽利略系统预计将于2009年投入使用。全球定位系统/伽利略系统的综合能力（统称为全球导航卫星系统）将使基于全球导航卫星系统的技术能够提高定位性能并实现经济增长。预计到2015年，全球导航卫星系统的销售额将达到2000亿美元。为了实现全球导航卫星系统的最佳定位性能，必须减少测距误差，并保持可靠的接收器跟踪能力。利用来自密集的全球导航卫星系统参考台站区域网络的观测，通过对测距误差进行建模，往往可以实现分米级的定位精度。许多这样的网络正在全世界实施。最大的测距误差出现在全球导航卫星系统信号穿过地球电离层和中性大气层时。对于恶劣天气事件和电离层风暴，准确地模拟这些影响是一个挑战。总体完整性取决于在存在电离层扰动的情况下是否有双频观测。该提案的重点是为加拿大未来的实时网络RTK应用开发改进的大气模型，并有可能在全球范围内实施。这包括利用新的GNSS发展的能力，确保可靠的接收器跟踪性能，并将新的数据源（例如无线电掩星和NWP）集成到新的建模技术中。这里提出的研究是及时和重要的发展这一关键技术为加拿大。

Since 1993, twenty-four or more GPS satellites have provided worldwide coverage and positioning capabilities. Enhancements to the GPS will take place in the near future and a European satellite-based navigation system, Galileo, is expected to be operational by 2009. Combined GPS/Galileo capabilities (referred to in general as Global Navigation Satellite Systems - GNSS) will allow improved positioning performance and economic growth for GNSS-based technologies. It is anticipated that GNSS sales will reach 200 billion by 2015. In order to achieve optimal GNSS positioning performance, ranging errors must be mitigated and reliable receiver tracking capabilities must be maintained. Decimetre-level positioning accuracies are often achieved by modeling ranging errors using observations from a dense regional network of GNSS reference stations. Many such networks are being implemented worldwide. The largest ranging errors arise as the GNSS signals travel through the Earth's ionosphere and neutral atmosphere. For severe weather events and ionospheric storms, it is a challenge to accurately model these effects. Overall integrity depends on the availability of dual frequency observations in the presence of ionospheric scintillations. The focus of this proposal is the development of improved atmospheric models for future real-time network RTK applications in Canada, with potential for implementation worldwide. This includes capabilities to exploit new GNSS developments, ensure reliable receiver tracking performance, and integrate new data sources (e.g. radio occultations and NWP) into novel modeling techniques. The research proposed here is timely and important for developing this essential technology for Canada.