Method for GPS and GNSS Independent MLAT System Synchronization

Soon our National Airspace will be flooded with flying unmanned aerial systems (UAS) from fixed wing drones to large aircraft. Multilateration (MLAT) is a method of determining the accurate position of aircraft by measuring the time-of-arrival of radio signals from those targets at multiple, static, ground-based sensors. It relies on those targets having an on-board transmitter (the transponder) which can generate its own radio signals and reply to interrogations from a ground station. MLAT offers many advantages over secondary surveillance radar (SSR) and - in many cases - can be used as an effective alternative to SSR. Advantages include compact, low-power equipment that can be installed easily on existing structures such as rooftops or cell towers, ability to expand coverage by just adding additional ground stations, and the ability to operate passively on signals not generated by its own interrogations, providing higher detection rates and accuracy.