UAV-Based Measuring System for Terrestrial Navigation and Landing Aid Signals

Terrestrial navigation and landing aid stations help a pilot to safely navigate and land an aircraft by using signals originating from ground-based stations. These systems need to be tested periodically toconfirm that their performance is within International Civil Aviation Organization (ICA0) limits. Currently, this test is performed by using a manned aircraft making several passes around the ground stations or along the runways. In this paper, an unmanned aerial system (UAS), called the positional information via GPS and encoded overlayed navigation signals (PIGEONS), is presented. The system employs a light-weight hexacopter, with a wingspan of 55 cm, that performs autonomous flight and uses an onboard software-defined radio (SDR) that measures the instrument landing system (ILS) and VHF omnidirectional range (VOR) systems. The UAS test system is designed so that flight coordinates can be preprogrammed, making it adaptable to different test locations. The system data is stored onboard while telemetry information is sent to the pilot during flight to inform them of the system's status. The ILS, VOR, and GPS measurements are analyzed once the UAS has completed the flight to determine the compliance of these guidance and landing aid systems with the performance requirements from the ICAO. Positioning measurement inaccuracies are reduced by using a Real-Time Kinematic (RTK) GPS. The ILS system was tested at DAB Airport in Daytona Beach, FL and the VOR was tested at OMN Airport in Ormond Beach, FL. The azimuth measurements for the VOR tower were taken between 292° and 328°. Two drive-bys were performed, and two moving averages were applied in post-processing to both passes using 50,000 and 100,000 samples. This resulted in average magnitudes of error between the measured data and reference GPS for the four passes of 4.18°, 5.34°, 2.24°, and 2.05°. Due to measuring limitations, the measured modulation indexes were limited, being bounded before hitting the 0.0 and 0.4 modulation indexes.