Accounting for tropospheric anomalies in high integrity and high accuracy positioning applications

This paper describes and quantifies the impact of tropospheric duct anomalies on the integrity risk of a high accuracy differential satellite-based navigation system. First, tropospheric ducts are defined, their causes are identified and their effects on differential satellite ranging signals are analyzed. Second, an error model for tropospheric duct is derived and a threat space is developed using 10 years of troposphere observations. Third, two approaches are introduced to establish protection level equations in the presence of tropospheric duct anomalies: a bounding bias approach and a more conservative, but less constraining sigma-inflation method. Finally, performance evaluations are carried out for an example aircraft shipboard landing application.