Monopulse secondary surveillance radar azimuth error distribution analysis

Radar data collected from three different monopulse secondary surveillance radar (MSSR) types are analyzed to assess azimuth measurement error characteristics. Aircraft radar position reports are compared with Global Positioning System (GPS) position reports delivered by Automatic Dependent Surveillance-Broadcast (ADS-B) for aircraft targets of opportunity. ADS-B positions are regarded as truth for error determination. The analysis procedure applies techniques developed to minimize timing discrepancy between ADS and radar position measurement systems to achieve best time registration and to minimize azimuth measurement bias for separate aircraft tracks in the population. Azimuth error probability distribution models that best fit the data are determined by a procedure that tests values for distribution parameters and maximizes the fit quality for Gaussian, double Gaussian, and Gauss-Laplace error distributions. The analysis found that azimuth errors for the general population of aircraft best fit a double Gaussian error distribution model. An analysis technique that removed the residual azimuth bias for individual aircraft tracks produced a result where the azimuth errors best fit a Gauss-Laplace error model. The double Gaussian result is representative of a surveillance system that applies techniques to generally remove azimuth and time bias. The Gauss-Laplace models a surveillance system that dynamically aligns and removes bias for individual aircraft.