Marine Radar Research Articles

シミュレーション画像を用いた船舶レーダによる２次元波浪パラメータの観測手法に関する研究

The Observation of two dimensional (2-D) wave parameter distribution is important for the estimation of the wave force to marine constructions, such as jetty. The in situ data routinely observed now are point data and the cost is expensive, so the number of observation point is a few. There is no routine method for monitoring 2-D wave parameter distribution.Marine radar can offer the image of 2-D wave field by monitoring the sea clutter from the sea surface. The data from marine radar is, however, analog data, so it is difficult to analyze 2-D wave parameter from the image.We are developing the data acquisition system from marine data now. Before the marine radar is calibrated by comparing in situ data, we proposed the method for monitoring 2-D wave parameter, especially wave length and wave direction, by using simulated image of marine radar in this study.Image of marine radar was simulated by FFT, when wave direction was 0, 30, 45, 60 and 90 deg. and wave length is 1/8, 1/4 and 3/8 of perimeter size of the target area. It is concluded that the accuracy of the proposed method in this study is concluded over 90% and it is accurate enough for operational use.

Development and application of MCAL tools for marine radar instruction

AbstractIn this article a multimedia computer‐assisted learning (MCAL) system is presented. The major objective of this work was to investigate the potential of using such systems as tools for transferring instructional course information through various types of computer media as opposed to the classic CAL systems. The philosophy and techniques employed to design the system are investigated. Usage of the implemented system and its merits have been illustrated through its application to teach engineering students and technicians the theory and concepts of marine radar. System design, implementation, test, and revision phases are presented and discussed.

Applying chaos to radar detection in an ocean environment: an experimental study

Ship navigation through ice-infested waters is a problem of deep concern to the oil exploration industry of Northern countries. Conventional marine radars do not perform satisfactorily in detecting small targets such as small pieces of iceberg. This paper reports a new method for detection in an ocean environment. The approach is based on the recent observation that sea clutter, radar echoes from the sea surface, can be modeled as a nonlinear deterministic dynamical system which can be used as an alternative to the conventional stochastic process. Based on this model, detection in sea clutter is considered as dynamical system classification instead of statistical hypothesis testing. Two dynamical detection methods are proposed. The first one uses a dynamical invariant called the attractor dimension to distinguish a target from a pure clutter process. The second approach tries to detect the existence of a target by observing the difference of the motion of the target and the clutter process. To show the validity of the idea of dynamical detection in sea clutter, real sea clutter, and target data were used in this study. >

Growler detection in sea clutter with coherent radars

Ship navigation through ice-infested waters is a problem of deep concern to the Canadian shipping and exploration industry. Conventional marine radars have difficulty detecting small pieces of glacial ice called growlers which are very hazardous to vessels if struck. In an effort to improve detection performance, X-band radar measurements were collected and analyzed to determine the characteristics of clutter and growler returns that could lead to their separability. These analyses suggested that coherent medium dwell-time processing (i.e., integration times of a fraction of a second) could provide improvement In growler detectability over conventional methods; and long dwell-time processing (i.e., integration times on the order of seconds) could provide even further improvement. We report on the performance of two new coherent, medium dwell-time detectors. A third detector which is representative of conventional marine radar serves as a basis for comparison Although significant improvement in growler detectability is achieved, the two coherent detectors still fall short of operational requirements. This leads to the development of a long dwell-time detector which provides considerably better performance. Empirical results indicate that this new detector could well satisfy stringent operational requirements. >

The grand banks ERS‐1 SAR wave spectra validation experiment: Program overview and data summary

Abstract This paper describes the observational framework for the research reported within this Special Issue. The validation of the ERS‐1 synthetic aperture radar (SAR) for ocean wave measurement was the primary goal and focus; secondary goals were the validation of wave models and marine radars and the investigation of the wind stress/sea‐state relation in the open ocean. The planned focus of the observations on the ERS‐1 crossover node location and pass times over the Grand Banks of Newfoundland, and on the grid points of the Atmospheric Environment Service's operational wave prediction model, has produced the opportunity for an accurate calibration and a relevant validation of the ERS‐1 SAR, the wave model and the marine radars. The observations, made on the Grand Banks in winter, strongly emphasize the complexity of the atmospheric and wave fields encountered in the open sea at these latitudes. Their interpretation will provide a challenge, and will require consideration of a wide variety of data sou...

Analysis of marine radar image spectra collected during the grand banks ERS‐1 SAR wave experiment

Abstract Remote measurements of wave spectra were made using MacLaren Plansearch's Marine Radar Wave Measuring System (Macrada©) for the duration of the ERS‐1 Grand Banks Experiment (10–27 November 1991). The system consists of a Furuno X‐band marine navigation radar and a personal computer. The system was installed and operated onboard the BIO Research vessel CSS Hudson during the experiment. The radar system provides fully directional wave spectra in real time (within minutes of image acquisition) as well as archiving of the raw images for future analysis. During each of the satellite overpasses, excellent data were collected, covering a variety of wave conditions. This paper describes the data analysis procedures and presents the results of the experiment. In addition, a sensitivity analysis is carried out to study: (1) sensitivity to the number of radar images processed on the resultant spectra, (2) effect of missing one or more images in a dataset, and (3) sensitivity to azimuth angle variation. Fina...

舶用レーダーによる波浪観測と解析-I : 陸上観測点における実験

The wave observation by a marine radar has been made 30 days in total for 3 years from 1991 to 1993 at the west coast of the Awaji Island. In 11-run observations, the wave directions and wavelengths of prevailing waves could be obtained from the data of radar sea clutter. The wave directions and wavelengths obtained by the 2-dimensional spectral analysis were not different from visually observed wave directions by 7 degrees and estimated wavelengths by 6m, respectively. The results of the directional 1-dimensional spectral analysis were also reasonably consistent with them of the visual observation and the 2-dimensional spectral analysis. Although the results of the directional 1-dimensional spectral analysis were less than them of the 2-dimensional spectral analysis in accuracy, the method of the directional 1-dimensional spectral analysis is useful in the automatic selection of the analyzing area for the 2-dimensional spectral analysis in the wave analysis system.

Growler detection in sea clutter using Gaussian spectrum models

Ship navigation through growler-infested waters is a problem of deep concern to the Canadian oil exploration industry. Growlers are small pieces of glacial ice weighing up to 100 tonnes. Conventional noncoherent marine radars do not perform well in detecting these small but dangerous objects. A coherent detector based on a Gaussian spectral width (GSW) parameterisation of received radar echoes from growlers and sea clutter is considered. Using real X-band radar measurements, the new GSW detector is shown to offer significant improvement in the detectability of growlers in the sea. Nevertheless, the performance achieved indicates that further integration is still required to satisfy practical performance requirements.

Marine Radar: A Selective Review of R&D and a Way Ahead

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Precision Aircraft Height Estimation with Horizontal Axis Marine Radars: (The Dual Autonomous Monitoring System (DAMS))

Civil aviation authorities have a requirement for the application of devices which are capable of determining the geometric height of aircraft above flight level 290 with a high degree of precision. These devices, called height monitoring units (HMUS), should pave the way for a safe and expeditious introduction of reduced vertical separation of 1000 ft above flight level 290.In this paper the design philosophy as well as the prototype development of such a device, which is called the dual-synchronized autonomous monitoring system (DAMS), are outlined. This device operates fully independently of any airborne equipment such as secondary surveillance radar transponders.The configuration basically consists of two standard marine radars with both axes of revolution situated in a horizontal plane. With this configuration it is possible to determine the trajectory of an aircraft and, in particular, the geometrical height above ground level within typical radar slant range coverage of some 18 km. The basic application of this equipment will be in the field of height monitoring of aircraft targets in environments with reduced vertical separation standards of 1000 ft above flight level 290, but a wider application of this concept is foreseen for local precision tracking of aircraft targets.

A Note on the use of the Global Positioning System (GPS) for the Identification of Marine Radar Contacts

The Global Positioning System (GPS) is a cheap, accurate (±100 m), satellite-based position fixing system. These qualities suggest that it might be used in the identification of marine radar targets. The first application of such a system on any scale will probably be as part of a Vessel Traffic Service (VTS) and here GPS would seem to be ideally suited. Vessels entering the VTS control zone would need to be fitted with GPS interfaced with either a dedicated VHF receiver or a ‘guard’ channel on their normal receiver A VTS radar operator needing to identify an echo would work out the echo's position from the radar range and bearing and transmit that position as the interrogating signal. Only the vessel in the control zone with that position (derived from its GPS interface) would respond with its identity. There would thus be no possibility of interference between responses or garbling that can be a problem in interrogation systems based on secondary radar. Even if the VTS had several radars, these could easily be synchronized to prevent simultaneous interrogations. However, outside VTS zones there is a clear need for a universal identification system that would allow any ship to identify any other. It would be unfortunate and wasteful if a system developed for VTS was found to be unsuitable for this general application. This note will therefore discuss the adequacy of GPS as the basis of a universal marine identification system.

Precision Aircraft Height Estimation with Multiple Radars

Civil aviation authorities have a requirement for the application of devices that are capable of determining the geometric height of aircraft above flight level 290 with a high degree of precision. These devices, called height monitoring units (HMUs), should pave the way for the safe and expeditious introduction of a reduced vertical separation of 1000 ft above flight level 290 (29,000 ft). This paper outlines the design philosophy, as well as the prototype development, of such an HMU, called the Dual-synchronized Autonomous Monitoring System (DAMS). This device operates fully independently of any airborne equipment, such as secondary surveillance radar transponders. The configuration consists basically of two standard marine radars with both axes of revolution situated in a horizontal plane. With this configuration, it is possible to determine the trajectory of an aircraft and, in particular, the geometric height above ground level within typical radar slant range coverage of some 18 km.

AR-based growler detection in sea clutter

A technique that performs better than conventional, noncoherent marine radars in detecting small pieces of glacial ice (growlers) in the sea is reported. A coherent detector based on an autoregressive (AR) parameterization of received radar echoes that distinguishes growler returns from the background sea clutter returns is considered. A conventional noncoherent detector is also evaluated as a basis for comparison. The AR-based detector is shown to offer significant improvements in detecting growlers. The results reported are based on real X-band radar data.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Low-altitude target detection by coastline operated marine radar

Relevant to a Richian family of fluctuating targets with a composite background of sea-plus-land clutter, the performance prediction of a radar operating in near-coastal regions is elucidated by assuming noncoherent integration of the pulses. Considering the dominance of land clutter, a modified K-distributed statistic is indicated for the overall clutter envelope; and the corresponding probability of false alarm and probability of detection are deduced for fixed threshold detection (s) based on N pulses integrated in the presence of the sea-plus-land clutter and the noise. Even when the target offers a dominant scattered echo, the worst situations of the land clutter affecting the detection performance are indicated. >

Civil Marine Radar Developments in the Eighties

This paper was presented at an RIN meeting on ‘Air and Marine Radar Developments’ on Wednesday 16 January 1991.During the last decade there have been significant developments in the civil marine radar field, resulting in: (1) Improved radar detection performance; (2) Improved operational facilities; (3) Improved reliability; (4) High brightness, daylight viewing, colour and monochrome displays with full ARPA performance; (5) Integrated radar and navigation systems; (6) Reduction in costs.

The Flight Behavior of Migrating Birds in Changing Wind Fields: Radar and Visual Analyses

This paper examines the influence of atmospheric structure and motion (principally winds aloft) on the flight behavior and altitudinal distribution of migrating songbirds. Bird migration data that I gathered using surveillance radars operated by the United States National Weather Service and the Federal Aviation Administration and a vertically directed fixed-beam marine radar mounted on a mobile laboratory are analyzed in relation to winds aloft. Migrating birds appear to fly at altitudes where winds will minimize the cost of transport and assist movements in seasonally appropriate directions. When migratory flights occur at altitudes that are higher than usual, a significant correlation exists between the altitude of densest migration and the altitude of most favorable wind. Lower altitudes may be favored over slightly more favorable winds at much higher altitudes. Radar data on the flight behavior of migrating birds in the vicinity of frontal systems is also examined. The flight strategies of migrants (fly over the front, change the direction of flight, or land and terminate the flight) differ depending on season and the “thickness” of the front. Recent migration studies that are related to atmospheric structure and motion are summarized and related to atmospheric processes operating simultaneously at vastly different spatial and temporal scales.

A Numerical Model of Internal Wave Refraction in the Strait of Gibraltar

Abstract The relative importance of depth, cross-strait interface till and horizontal current shear upon the wave front shapes of internal waves in the Strait of Gibraltar are examined by means of a numerical refraction model. Results from the model are also compared with observations of wave front shape made in the eastern strait using a shore-based marine radar, which imaged the surface effects of the waves. The model is linear and assumes a time-independent two-layer fluid in which the depth of each layer may be any function of position. The effect of current on the propagation is modeled by the addition of a term in the dispersion relation that increments the phase speed by an amount equal to the current component in the propagation direction, at the depth of maximum internal wave displacement. This current may also be any function of position. The results suggest that in the Strait of Gibraltar, interface tilt and horizontal shear both have a strong influence on the refraction, whereas total depth is...

New slotted-waveguide antenna element for low side-lobe arrays

Conventional slotted waveguide array antennas, such as those commonly used in marine and airborne radars, tend to suffer from the presence of either double periodicity lobes or cross-polar lobes, or both, in their far-field radiation patterns, and these inhibit the creation of very low side-lobe designs. A number of possible schemes aimed at eliminating these error lobes have been proposed and these are reviewed. The impracticability of the majority of these schemes has led to the evolution of a new slot geometry that overcomes most of the difficulties associated with earlier arrangements.

Real-time radar detection of iceberg shadows

The Hough transform is used to estimate the radial direction of shadows cast by icebergs in surface-based marine radar returns using a Warp systolic computer. Automatically locating these shadows leads directly to automatically locating the icebergs casting the shadows. This is useful for the unattended navigation of a vessel through sea ice, as well as for improving the accuracy of a classified sea-ice image. The results reported show that the Hough transform can successfully estimate the radial directions of the shadows cast by the icebergs, and that the implementation on the Warp computer is commensurate with a real-time requirement for shadow detection. >

A Study of Internal Wave Propagation in the Strait of Gibraltar Using Shore-Based Marine Radar Images

Abstract An X-band marine radar on Windmill Hill, Gibraltar, was used to monitor the propagation of internal waves in the Strait of Gibraltar during March, April, and June 1986. Surface roughness features of the waves were observed out to a range of ∼15 km. From photographic images of the radar screen, the positions of image features were measured manually using a digitizing table, and these data were then computer processed to give wave arrival times and phase speeds. During most tidal cycles, an internal undular bore generated at Camarinal Sill was observed to pass eastward (A-waves). These occurred throughout the experiments although less frequently near neap tides. The time of travel to Gibraltar varied significantly, so that the bore arrived between four and nine hours after high water. Arrival times were found to be closely related to the amplitude of the upper layer tidal current. This current had a strong diurnal component, which was manifested as an inequality between the arrival times of success...