Time-Differenced Carrier Phase Based Integrity Monitoring in Urban Environment

Precise positioning is crucial for advanced transportation systems like autonomous vehicles and Urban Air Mobility (UAM). However, urban environments pose challenges for GNSS-based navigation due to satellite signal blockages and severe multipath errors. Carrier phase measurements, known for their low noise, offer a precise solution but require resolving integer ambiguity. Time Differenced Carrier Phase (TDCP) eliminates this ambiguity through time differencing, enabling precise navigation without the need for ambiguity resolution. TDCP-based Receiver Autonomous Integrity Monitoring (RAIM) enhances navigation reliability, which is critical for UAM operations in urban areas. TDCP-based RAIM method uses a fixed time interval between the two consecutive carrier phase measurements. Unlike conventional RRAIM, TDCP RAIM has the advantage of having more measurements in a changing satellite condition. Additionally, it maintains continuous positioning and protection levels even when satellite visibility is reduced. Previous studies validated TDCP RAIM through simulations with 3D building models. This study evaluates its real-world performance using urban test data, demonstrating its feasibility for precise and reliable UAM navigation.