Aircraft Navigation with the Limited Operational Phase of the NAVSTAR Global Positioning System

Abstract

The navstar Global Positioning System (GPS) will soon be in the limited operational phase. During this phase, a GPS user will not generally be able to determine his position using satellite measurements only. This paper describes the simulation of an aircraft navigation technique which uses the limited operational phase GPS and barometric altimeter measurements. For this research effort, the GPS user was assumed to be a cargo–type aircraft equipped with a single–frequency, sequentially–tracking GPS receiver and a barometric altimeter. The flight profile consisted of a New York to Chicago flight and included takeoff and landing maneuvers. A small amount of wind gusts were simulated. To make the simulation more realistic, random effects were included in the user and satellite clocks, in the atmospheric radio delays, and in the measurement process itself. The tested navigation algorithm is based on the well-known Kalman filter equations. Three different models of aircraft acceleration were evaluated. Results indicate that, for a wide range of filter parameters, navigation errors are generally less than 100 meters. Poor geometry, however, results in kilometer–sized position errors.