Use of High Altitude Platform System (HAPS) to Enhance a GNSS Backup Ground System

Abstract

Global Navigation Satellite Systems (GNSS) have been chosen to be the primary means of navigation for aviation. They are already used by most aerial vehicles, from major aircrafts to small UAVs. But GNSS is easy to interrupt because of the low signal strength coming from the satellites. Therefore, an Alternative Positioning Navigation and Timing (APNT) system is necessary as backup for a safety application. The systems currently under discussion for APNT make use of signals sent or received from stations on the ground, hence they can only aim at providing enough accuracy on the horizontal domain. In this paper, we propose a hybrid system that makes use of ranging sources from ground stations along with one or more High Altitude Platform Systems (HAPS) to provide a robust navigation system with a good geometrical diversity. This especially improves the vertical position information for the airborne user.