HoJoon Jeong, Changdon Kee, Department of Aerospace Engineering and SNU-IAMD, Seoul National University; Junesol Song, Division of Mechanical Engineering, The University of Suwon; Jungbeom Kim, Samsung Electronics system LSI

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In this study, we developed a method for integrity monitoring in urban area by using time differenced carrier phase (TDCP) measurement that is less susceptible to multipath errors compared to pseudo-range measurements. This method does not require a cycle ambiguity resolution because it uses Time Differenced measurements to obtain a relative position and to conduct the integrity monitoring. Relative Receiver Autonomous Integrity Monitoring (RRAIM) already exists as a conventional RAIM technique using a TDCP measurement and the SBAS-based initial position. In the RRAIM, two time points at which the carrier phase measurements are time differenced consist of a current time point and a fixed initial time point. In this case, only the number of visible satellites that are common at the current time and at the initial time is used to estimate the relative position. Therefore, RRAIM cannot benefit from the increased number of satellites after the initial time. Moreover, in urban environment, the integer ambiguities of carrier phase measurement may change due to the temporal loss-of-lock tracking of the satellites by building blockage, and this carrier phase measurement cannot be used by RRAIM algorithm. To overcome this limitation of the RRAIM, we propose a TDCP-based RAIM method where the time interval between the two carrier phase measurements is fixed to a sampling time (i.e. 1second). In order to confirm the performance of the proposed method, we conducted a simulation of a drone landing in an urban area. The result of a simulation indicate that the proposed integrity monitoring method can maintain the SBAS performance in urban area, which cannot be achieved by RRAIM.