Yasuo Arai

On the Effect of Plotting Performance by the Errors of Pointing Targets in the ARPA System

The effect of different measurement points on an acquired target is theoretically investigated with respect to the ARPA (radar-computed anti-collision) plotting performance. The target is described by simple geometrical figures and the echo is simplified. The actual measurement position is generally not at the centre of the target. This may cause errors in the standard plotting results. The characteristics of these errors are discussed from a nautical viewpoint.

The Propagation Characteristic of DGPS Correction Data Signal at Inland Sea - Propagation Characteristic on LF/MF Band Radio Wave

Users of the Inland Sea require high position accuracy, which is 5 m (2 drms) or less. Therefore the position accuracy of standalone GPS is insufficient. Consequently, it is necessary for a navigator sailing the Inland Sea to use DGPS. The authors executed numerical simulation of the propagation characteristic on the extended line of bridge pier at opposite side from DGPS station, and already confirmed that bit error in DGPS correction data signal occurs, and that correction data could not form with bit error. Furthermore, they carried out numerical simulation of the propagation characteristic of DGPS correction data signal received at sailing through center of the bridge, and solved receiving condition of DGPS correction data signal before and after passing through the bridge. In this paper, the authors inspected results of electric field intensity simulation for oversea and overland propagation on some sea area of the Inland Sea and measured results of electric field intensity for DGPS correction data signal. They evaluated the possibility of abnormal propagation comprehensively.

Wave remote sensing system by GPS

It is well known that an observation of the long period gravity wave is very difficult to observe for its long period and small amplitude. In our recent research, an integrated wave remote sensing system utilizing multi-path GPS signals reflected from sea surface is proposed to measure accurate wavelength for long period gravity wave. The system is equipped with an arrayed GPS antenna that has a narrow fan beam directional pattern. It has a better performance to measure accurate wavelength than wide beam antenna in numerical simulation and it can acquire multi-path GPS signal reflected from specified sea surface in seaside experiments. In digital GPS signal processing, software GPS receiver is applied to estimate the relative time delays between multi-path GPS signals. In this paper, simulation results and seaside experiment results obtained by the wave remote sensing system are also presented.