Shogo Hayashi

A stranding avoidance system using radar image matching-development and experiment

Describes a fully automatic stranding avoidance system that can replace more orthodox methods. The automatic system uses radar matching to obtain position with high precision and to make judgements concerning the danger of stranding. Several field trials have been conducted on the Japanese training ship Shioji Maru.

STUDY TOWARDS A 21ST-CENTURY INTELLIGENT SHIP

Recent technological developments and the emergence of new, high-tech materials have led to the concept of a new type of ship and to innovations in ship operation. A Japanese research team is studying ways of designing a ship for the future. This paper focuses on the optimum automatic operation system for oceanic navigation in a future ship. See also the following abstract.

Radar signal detection in non-Gaussian distributed clutter by Bayesian predictive densities

We present a coherent radar signal detection scheme in non-Gaussian distributed clutter and its simulation results. In this scheme the clutter is modeled by compound Gaussian distribution and unknown parameters, i.e. target amplitude and clutter, are estimated based on a posteriori distribution with a noninformative prior. Also a technique called Bayesian predictive densities is employed. In order to investigate the performance, we carried out the Monte Carlo simulation and its results are also compared with conventional detection schemes such as maximum likelihood and maximum a posteriori estimator. The simulation results show its usefulness.

Target detection in ground clutter with stepped frequency CFAR detector at millimeter-wave

This paper presents a constant false alarm rate (CFAR) stationary target detection scheme in ground clutter at millimeter-wave frequencies. The proposed scheme makes use of the clutter decorrelation bandwidth considered in the stepped-frequency radar system and the concept of a CFAR matched filter for the received data projection onto the signal and clutter subspace. Therefore, the scheme achieves the CFAR, where the knowledge of the clutter covariance matrix is not needed preliminarily. In order to investigate the detection performance, we carried out experiments with a W-band stepped-frequency polarimetric radar system at 94 GHz with a bandwidth of about 300 MHz. The results are discussed and compared with conventional CFAR detectors.

Power transmission line detection using an azimuth angular profile matching scheme

This paper presents high-voltage power transmission line detection with millimeter-wave (MMW) radar for the purpose of helicopter collision avoidance. In order to improve the detection, an azimuth angular profile matching (APM) scheme of the power transmission line based on the Bragg scattering phenomenon is suggested. For the evaluation of detection, we carried out a Monte Carlo simulation both at 94 GHz and 35 GHz, where a white Gaussian noise is considered as an additive noise. The results show that the detection probability with the APM at 94 GHz is much higher than that at 35 GHz and the detection performance is much improved by employing the APM.

Empirical study of polarization techniques for clutter reduction

This paper discusses the feasibility of clutter reduction by a radar polarization technique for the signal-to-clutter ratio (S/C) improvement. The polarization dependency on surface roughness is numerically investigated and the measurement for a target model is also carried out at 94 GHz.

Land-based evaluation on dynamic accuracy in position provided by Global Positioning System

The authors examine the dynamic accuracy in position provided by the Global Positioning System (GPS), since most operations are conducted while moving. Thus, what is required in this case is not statically, but dynamically, high accuracy. However, few systems are available to get a fixed position at high accuracy for dynamic maneuvering, and the analysis of the dynamic data requires a position-by-position comparison. A dead reckoning system with excellent accuracy has been used for the comparison to GPS position. The value of the results derived using this approach depends heavily on careful synchronization of time during the tests carried out. The results obtained through the latest dynamic tests and applications for future navigation are discussed.<<ETX>>

A PROCESSING METHOD OF RADAR SIGNAL TO DETECT DRAGGING ANCHOR

The authors have studied the possibility of detecting the dragging of a ships anchor by using a technique of radar image processing. The video signal was converted to an 8 bits digital signal at a 40 nanosecond sampling rate and stored in the 1 megabyte memory of a personal computer in order to measure the 2-D distribution of echoes. Using this data, the position, attitude and change of attitude of the ship were examined. It was concluded that a large number of further observations will be needed to establish a more accurate processing method. See also Abstracts Nos. 89013076, 89013082 in this issue.