Space weather predictions service for safety-critical GPS applications

Enhanced ionospheric effects may exist during space weather events, leading to degradations in GPS performance and positioning accuracies. This issue is a concern for reliable operation of safety-critical GPS systems, such as marine DGPS services or Satellite-Based Augmentation Systems (SBAS) for aviation applications. These storm-related effects tend to peak in the years following solar maximum, and will continue to be a concern for GPS applications over the next few years (2002-2003). In order to provide timely predictions of space weather events, we have recently investigated an ionospheric warning and alert system for GPS applications. Predictive capabilities are based on space weather parameters provided by the United States Space Environment Center at NOAA. The impact of ionospheric activity on GPS performance has been quantified using several years of GPS data from the North American sector, with a focus on marine and aviation applications. We have established strong correlations between GPS performance and various ionospheric phenomena, and we are able to provide space weather predictions for GPS users up to six hours in advance.