Navigation Radar Research Articles

Application of Bearing and Distance Trees to the Identification of Landmarks on the Coast

Application of Bearing and Distance Trees to the Identification of Landmarks on the CoastThe problem of continuous position availability is one of the most important issues connected with the human activity at sea. Because the availability of satellite navigational systems can be limited in some cases, e.g. during military operations, one has to consider additional methods of acquiring information about the ship's position. In this paper one of these methods is presented, which is based on exploiting landmarks located on a coastline. A navigational radar is used to obtain information about these points. In order to estimate the ship's position by means of a set of landmarks, it is necessary to know their accurate locations. The paper presents a landmark identification method based on the comparison of bearing and distance trees representing pattern points generated from a chart, as well as points extracted from a radar image.

Non-coherent radar CFAR detection based on goodness-of-fit tests

This paper considers the problem of constant false alarm rate (CFAR) detection of radar targets using multiple observations. In the Gaussian clutter scenario, the structure of the optimum (uniformly most powerful) CFAR detector is rather simple, but when the clutter is heavy-tailed, that is non-Gaussian distributed, the derivation of the optimal detector becomes infeasible. For this latter relevant case, a new CFAR algorithm is porposed based on goodness-of-fit (GoF) tests. The performance of the proposed detector is numerically investigated through Monte Carlo simulations assuming heavy-tailed Weibull and Lognormal distributed clutter. Numerical results shown that, in heavy-tailed clutter and also when several interfering targets exist, the proposed detector outperforms the conventional CFAR detector based on binary integration. Performance is also tested processing real sea clutter data collected by a non-coherent navigation radar.

Off-highway obstacle detection

The biggest conclusion is that intensity of radar backscatter returns is a poor indicator of danger to a vehicle despite the attempts of several projects to show otherwise. Still, our method violates this finding at some level. An image of backscatter intensities is filtered with various image processing techniques then is thresholded as if it has become an image of risks or confidences. Current research is investigating discriminant functions that allow arbitrary numbers of classes and can use separability and discriminability as confidences instead of a filtered version of intensity. It cannot be overemphasized that this system was designed as an add-on sensor to an already operable autonomous vehicle. As such, it is not sufficient as a primary or stand-alone sensor in an unstructured environment. Radar techniques to detect road edges [Kaliyaperumal et al., 2001], [Nikolova and Hero, 2000] or terrain quality would fill these gaps and allow a radar-only, all-weather autonomous platform. Autonomous radar navigation is possible with proper scoping of the problem. On highways this means ignoring cross-sections smaller than a motorcyclist. Off highway the solutions must be a little more creative, but still exist. Applying image processing techniques already well developed by the computer vision field and avoiding the assumption that intensity of backscatter is a feature directly related to obstacle danger will help advance this goal. Small radar systems have recently become very good, but they do not solve the problem alone. Just as other sensors like cameras and LIDAR require algorithms to convert from raw data to obstacle classifications, so too should radar users not expect to achieve good performance by simply thresholding the output from hardware. If radar is seen as just another imaging source like a camera, much work can be accomplished using the existing arsenal of image processing

Better Kohonen Neural Network in Radar Images Compression

Maritime radar image may be a basis for a perspective ship position fixing system. Images obtained from navigational radars possess usually great amount of information. Using all of these information is usually practically impossible. It is necessary to compress information imbedded in each image to the size acceptable from the practical point of view. Such an effect may be obtained by application of feature extraction methods. This article presents one of such methods that is based on capabilities of modified self-organizing Kohonen neural network.

Using the Signals Reflected from Sea Surface for Prediction of Coverage Range of Marine Navigational Microwave Radars

Experimental dependence is established between the range of observation of reflections from sea surface ("illumination" zone) and detection range of above-water object in microwave band. Methods are suggested of diagnostics of coverage range of marine navigational radars beyond radiohorizon. Results are compared of the coverage range prediction with real data obtained experimentally in various regions of the World Ocean.

New possible roles of small satellites in maritime surveillance

The introduction of AIS will change maritime surveillance in the future. We explore how satellites can complement or extend this cooperative surveillance technique. Radar satellites alone are not sufficient. Micro-satellites carrying sensors for reception of navigation radar pulses or AIS signals, offer some promising options.

Mobile terminal location for UMTS

Interest in mobile phone location is expanding due to the implementation of the third generation (3G) multimedia phones. The initial need for accurate terminal positioning has been motivated by government authorities, mainly by the US FCC's E911 mandate for emergency services. In Europe, similar ideas have appeared but the primary interest is in commercial value-added functions. Systems resembling air navigation and secondary radar as brought down to street level and pedestrian speeds are also foreseen. This article presents an overview of UMTS mobile terminal location. The performance of standardized observed time difference of arrival (OTDOA) and a novel database correlation method (DCM) for wide bandwidth systems are evaluated through simulations in an urban microcell environment. DCM is shown to provide a reasonable location error of 25 m for 67% of the calls. The obtained respective OTDOA accuracy is 215 m only. Location problems encountered in built-up areas and relevant applications based on the obtained accuracy are discussed.

操船シミュレータの水平視野角と現実感の関係 : 重心動揺と鼻部皮膚温の計測

The purpose of this paper is to find relations between a horizontal angle of visual field and it's reality created by a ship handling simulator at Radar Navigation Experiment and Research Facility in Kobe University of Mercantile Marine. We measure subjects' center of gravity and nasal temperature for body and physiological response to the artificially created visual environment. We carried out the experiment, which was simulated ships rolling only visually not mechanically from 0.0 to 20.1 degrees, and its rolling was controlled by changing wave height from 0 to 8 meters. The subject looked visual environment for one minute in each condition. The results show that the displacement of the subjects' center of gravity is led toward an inclination of the picture created by simulator and their induction sense is proportional to a horizontal angle of visual field. Then the relations between rolling angle and direction of center of gravity are approximated to a logarithm curve in 210 degrees well, and the nasal temperature decrease while the subject looks a visual environment.

シミュレータによる他船視覚情報からの主観的衝突のおそれについて

In good visibility, the expert navigator can collect some efficient information through the scene of sight, and he quickly and properly chooses any dangerous vessels. Next if he recognizes that a risk of collision will exist, he alters of his course or speed to avoid the collision for safety navigation. On the other hand, the inexperienced cadets like a trainee collect some information through same scene of sight, but they are not able to quickly and properly choose dangerous vessels. They have some different cognition through same scene of sight. In this paper, some elements (distance, azimuth, aspect angle, DCPA, TCPA) to cognize a subject risk of collision are discussed, and in some experiments of the radar navigation simulator it is shown that the most remarkable cognitive difference between a deck officer and a cadet for the cognition of subjective risk of collision at a short distance below one mile.

Hypothesis of Natural Radar Detection and Navigation Systems Guiding Hornets Flight

The hypothesis of a natural sophisticated RADAR navigation system guiding hornets flight and detecting obstacles and preys is derived from the investigation of the complex spike elements arrays on their cuticle skin shown by electronic microscope pictures. The occurrence of three different lengths and disposition of the spike elements lead from analogy with antenna and radio theory and practice to the hypothesis of transmitting and receiving phased arrays antennas operating at different frequencies in the sub-millimetric wavelength bands. The natural photo and piezo electric generation of energy in the hornets found previously explain how can be obtained the Radio Frequency (RF) energy required for the operation of the natural RADAR system. In this paper are presented a comparison with the bats well known sophisticated sonar tracking system and a description of the possible operation and main parameters of the complex three mode detection and tracking hornets natural RADAR. Following a discussion of the possible experimental and theoretical investigations still required for reaching final conclusions on a precise model of a sophisticated hornets tracking three mode RADAR system. It is possible that the results of the proposed investigations will provide tools to improve real tracking system performances especially in the yet not operative submillimeter wavelength ranges.

Rainfall measurements with navigational radar

A novel approach to measuring rainfall in the ocean is presented. The method is based on the remote sensing of rain by navigational radar and subsequent calibration of the radar signal against the upper ocean salinity changes. The estimate of the area‐average precipitation is obtained as the product of the calibration factor and the fraction of area covered by rainfall. We describe an application of this technique in the field during a recent voyage of the Australian R/V Franklin to the eastern tropical Indian Ocean. It is suggested that with further refinement of radar signal processing, navigational radar can be used to routinely measure open ocean precipitation from research vessels and ships of opportunity.

Hypothesis Stipulating That a Natural Radar Navigational System Guides Hornet Flight

Our hypothesis of a natural sophisticated radar navigation system guiding hornet flight is derived from an investigation of the complex arrays of spike elements revealed on vespan cuticle by electron microscopy. The occurrence of three different lengths and dispositions of these elements has led us to draw an analogy with the antennae associated with radio theory and practice and thus to hypothesize that they represent three transmitting and receiving phased arrays operating at three different frequencies in the sub-millimetric wavelength range. The natural thermo-photo and piezoelectric generation of energy in hornets, reported previously by us, could provide the Radio Frequency (RF) energy required for the operation of such a natural radar system. A comparison is made with the sophisticated sonar tracking and navigational system of bats vis-a-vis the mode of operation and main parameters of the three prolonged detecting and tracking system of hornets. We stress the need for further experimental and theoretical investigations before reaching decisive conclusions and propounding a precise model for the suggested radar system of hornets. Results of these further investigations may possibly provide means for improving vespan tracking and navigation, especially by exploring as yet unused submillimetric wavelength ranges.

The AN/ASN-128B: An Integrated Doppler/GPS Navigation System for Helicopters

The successful deployment of GPS has introduced a new and powerful tool that enables the development of a variety of integrated navigation systems. One such system integrates GPS with a Doppler radar navigation set, resulting in a system that combines the best features of each of the two sensors. The advantages of a combined system include the availability of accurate navigation even when one of the two sets of sensor data is not available, continuous updating of Doppler present position with the highly accurate GPS data, and use of Doppler velocity data to aid the GPS receiver for improved tracking in high dynamics and in a jamming environment. This paper presents a description of the AN/ASN-128B; test methods employed by the Army to verify its performance; and the growth of the AN/IASN-128B, including the use of a newer GPS card that meets the GPS Receiver Application Module (GRAM) requirements.

The use of low cost FM-CW radar sensors in navigation

Navigation of Autonomous Guided Vehicles (AGVs) has traditionally been accomplished by means of fixed path navigation systems. The trend towards the use of such vehicles in unstructured external environments has led to a requirement for increasingly sophisticated sensory inputs. This paper describes the use of FM-CW radar for autonomous vehicle navigation and the development of a real time test platform for their evaluation. Experimental results have been processed off-line using Matlab to extract range information. Real time performance was achieved using a dual processor system comprising a Motorola 68000 single board computer for system control and supervision and a Texas Instruments Digital Signal Processor, TMS320C50, for performing 1024 point Fast Fourier Transformation to convert a digitised radar return signal into a frequency domain signal.

Physical optics analysis of the field backscattered by a depolarising trihedral corner reflector

A physical optics (PO) model is developed to analyse the backscattering properties of an anisotropically loaded trihedral corner reflector, which can be obtained from the conventional triangular one by corrugating one of its interior faces. In such a way it can present a dihedral-like polarisation response over a wide angular range in both azimuth and elevation, thus making it particularly attractive for use in polarimetric radar systems as a location marker for radar navigation, and as a ground reference target in remote sensing applications. In fact, it can be designed to return elliptically or circularly polarised waves with the same handedness as the incident ones, and to rotate the polarisation of linearly polarised incident waves by 90°. The proposed model treats the corrugated surface as an anisotropic impedance boundary condition (IBC). Moreover, it evaluates in explicit form both the illuminating electric field related to the direct, singly and doubly reflected rays incident on each corner face and the shape of the corresponding illuminated patches. This allows a closed form evaluation of the related PO backscattering integrals, which produces a very fast computer code also suitable for non-powerful computers.

The Development of Shipborne Navigational Radar

This paper was first published in the Journal in 1947 (Vol. 1, p. 118). Sections 1 and 2 are summarized in order to save space. Sections 3, 4 and 5 are reprinted with only a little abridgment. The paper is followed by comment from the original author.The original paper gave a comprehensive account of the development of navigational radar in the United Kingdom from the beginning of World War II up to the time of writing.The use that was made of the very early radars was mentioned and the improvements brought about by the introduction of the PPI (Plan Position Indicator) and centimetric radar were described. An account was given of how radar assisted the Normandy landings, and of the techniques employed including the use of radar predictions of the Normandy coastline (produced in great secrecy) which were optically superimposed on the PPI. Also shown on the predictions were the planned approach tracks to the shore. An example of one of these predictions compared with the post-invasion radar photograph is shown in Fig. 1. This superimposition of geographical information on the PPI was to become of great significance in later years.

Directional Wave Navigation Radar Measurements Compared With Pitch-Roll Buoy Data

Abstract The knowledge of the spectral behavior of a specific sea region is complete when we know surface elevations and directional wave movements. Usually, sea directional descriptions have been made using pitch-roll buoys, which can provide us with several wave characteristic time series. Alternatively, there are other measure systems, which belong to remote sensing technics, such as shipboard navigation radars. The aim of the present work is to compare results obtained from pitch-roll data and ship radar wave measurements obtained during a campaign in the Cantabric Sea.

A Calibration Algorithm for Circular Polarimetric Radars

Since circular polarimetric radars can be used to assess the relative contribution of odd-bounce and even-bounce scattering to the response of targets and to implement novel schemes for adaptive rain clutter suppression and radar pulse compression, they are increasingly used in applications such as radar meteorology, biophysical and geophysical remote sensing, and radar navigation. Although methods for calibrating linear polarimetric radars are widely known, they cannot be used to calibrate circular polarimetric radars until account is taken for the different form of the response of calibration targets when measured with respect to a circularly polarized basis. The response of three standard targets used to calibrate linear polarimetric radars (an odd-bounce-reflector and two even-bounce reflectors with different angles of rotation about the radar line-of-sight) does not yield a unique solution to the calibration equations. If, however, the odd-bounce reflector is replaced by either a circularly polarizing or linear polarization selective target, the calibration equations can be solved.

GPS-Aided Lane Marking and Reporting for Shallow-Water Mine Neutralization

This paper investigates the use of GPS to assist with the marking and reporting of lanes cleared of mines in preparation for a military amphibious assault. The feasibility of using GPS, inertial navigation systems (INS), GPS/INS, GPS translators, radar, laser, and videometric technologies is included in the concept study. Sensor data from the mentioned devices have potential for enhancing overall system performance and/or mission success during shallow-water mine countermeasure operations. The main objective of the study is to assess the advantages and disadvantages of the various sensor technologies as regards cost, accuracy, ruggedness, size, weight, power, and other considerations. With regard to GPS, dynamic robustness and vulnerability aspects are reviewed. Both differential and absolute GPS positioning accuracy are discussed for present and future systems within the constraints of the amphibious application. A discussion of the background for the study and the assumed scenario and environment for the operation is presented. Recommendations and conclusions are given.

The HAL-3 airborne navigation radar

This correspondence describes the HAL-3 navigation radar which was designed specially for civil airplanes. The main technical functions of the radar have been extensively tested on Boeing 707 and Y-7A airplanes to the military standard on aeronautic airborne facilities. The test results (1985) are qualified by the Chinese Appraisal Committee of Aeronautics Facilities. The technical specifications of the radar are similar to those of the RDR-1F radar manufactured in the U.S. with several added operational functions. The radar includes 7 units: antenna, transceiver, servo unit, control box, two display units and power supply. Operational principles and functions of each unit are described briefly. The current research project for interfacing the radar to a fibre-optic gyroscope is in process and some initial experimental results are described.