Flight Evaluation of IRS Positioning Errors & GPS Altitude Errors

Abstract

Automatic Dependent Surveillance (ADS) is a new surveillance system using a data link for air traffic services. Basic ADS Block, one of the data blocks in ADS report, includes a three-dimensional position, time and Figure of Merit (FOM). FOM is a newly-adopted performance index represented by 8 levels that notifies the capability of on-board navigation system to air traffic controllers. Each level is defined by 95% probabilities of position determination errors.

We evaluated positioning errors of Inertial Reference System (IRS) with respect to GPS-derived positions, to validate the correctness of FOM levels by flight tests. We also evaluated GPS-derived altitude variation with respect to Air Data Computer (ADC)-derived ones.

We devised a new method to analyze the IRS positioning errors and showed the variations of IRS positioning errors to the flight progress.