Mitigation of atmospheric effects on GNSS

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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.