In this paper, we design and evaluate a low‐cost multi‐antenna GPS/INS capable of producing highly accurate attitude for small UAVs. The main disadvantage of low‐cost GPS/INS based on MEMS inertial sensors is that the typical yaw angle accuracy is limited to 0.5‐2 deg. In this regard, a GPS compass using carrier phase measurements can achieve higher attitude accuracy. However, fast and reliable ambiguity resolution using low‐cost GPS L1 receiver modules is a challenging task for small and highly maneuverable UAVs. In the proposed method, a tightly coupled GPS/INS is tightly integrated with a GPS compass, which allows for an effective and reliable ambiguity search to be performed on the basis of the attitude as estimated by GPS/INS with a couple of constraints for the base line vectors. The in‐flight performance of the proposed GPS/INS was verified through hardware‐in‐the‐loop simulations and experimental flights.
GPS observations with higher than once-per-second sampling are becoming increasingly important for seismology. A number of reports have shown that very-high-rate GPS receivers are capable of capturing dynamic ground displacements from significant earthquakes. The higher output rate, however, does not necessarily mean higher frequency content of the corresponding observations. In order to examine dynamic effects on very-highrate GPS observations, the frequency response characteristics of several geodetic GPS receivers were evaluated using a GPS signal simulator in controlled laboratory conditions. The tested receivers include Trimble Net-R8, NovAtel OEMV, and TOPCON Net-G3A. The experiment results suggest that the dynamic characteristics of the signal tracking loops put a limit on the frequency of the received signals, and all the tested receivers except for Trimble show good signal tracking performance at up to 5 Hz under dynamic stress of 2 G acceleration. The power spectral densities of the kinematic solutions obtained from the simulated seismic motion of the 2008 Iwate-Miyagi Inland earthquake (M w 6.8) are also evaluated. The power spectral densities of both the NovAtel and TOPCON receivers agree with the simulated ground displacement at up to 5 Hz. By contrast, the Trimble receiver provides a pronounced increase in spectral energy above 2 Hz.
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