Accuracy Of Radar Measurements Research Articles

Azimuth and Origin Correction Method for Improving Radar Measurement Accuracy

Azimuth and Origin Correction Method for Improving Radar Measurement Accuracy

Coherent DOA Estimation in Sea Surface Observation With Direction-Finding HF Radar

The direction-finding high-frequency (HF) radar that employs a crossed-loop/monopole antenna as receiving has been widely applied in sea surface dynamics remote sensing due to its compact footprint and remarkable performance. Nevertheless, the direction-of-arrival (DOA) estimation of this system remains challenging in the case of coherent signals, which imposes a great threat to the radar measurement accuracy but has rarely been concerned in the past. In this article, a novel method combining the covariance matrix reconstruction process and subspace estimation technology is proposed to deal with this problem. By exploiting the purely real property of the array manifold, the rank loss of the covariance matrix due to the coherence of signals is mitigated. Both the theoretical derivation and numerical analysis prove that the proposed method is valid in estimating two coherent signals, and the DOA estimation accuracy is mainly related to the signal-to-noise ratio (SNR) and angle separation of the signals. Finally, field experiment data are also used to validate the effectiveness of the proposed method.

Method for increasing the resolution and accuracy of radar angular measurements based on sequential spatio-temporal processing of received signals

Introduction: Increasing requirements for the location accuracy of radar stations, along with the minimization of their structural changes, necessitates the use of special mathematical algorithms for digital signal processing. The use of such algorithms makes it possible to increase the resolution of a radar station up to a superresolution exceeding the Rayleigh resolution, without any constructive modification of the antenna systems. The existing superresolution algorithms require a large computational cost and a long signal accumulation time. Purpose: Obtaining superresolution in the angular coordinates of a linear antenna array due to digital synthesis of longitudinal flat aperture in real time by digital methods. Methods: An amplitude-phase distribution is formed on the elements of a linear lattice of the data array. On this base, a longitudinal flat aperture is synthesized using digital modeling algorithms for “virtual re-emission” of the received signals. Results: Based on the proposed method of synthesizing a linear antenna array aperture in the longitudinal plane, an algorithm was developed for estimating the increase in the angular resolution of the linear antenna array. Computer simulation of the resulting lattice was performed, and its radiation pattern was built. The dependence was analyzed of the angular resolution on the phasing direction and on the synthesis interval when using this method. Quantitative assessments were carried out by the comparison between the obtained angular resolution and a potentially possible one determined by the Rayleigh criterion. The resolution in angular coordinates when using this method increases by 1.5 times. Thus, the proposed method allows you to increase the angular resolution of a radar station without any significant structural changes in the antenna array, using relatively simple algorithms. Practical relevance: The application of this method in radar stations, especially those operating in the short-wave range where increasing the size of the antenna array is a rather difficult task, will improve the radar measurement accuracy.

Hybrid Particle/Extended Finite Memory Filter to Improve Target Tracking Accuracy of Radar Measurement in Harsh Environments

Although the particle filter (PF) generally provides accurate estimation, it fails in harsh environments, such as severe signal noise and/or abrupt state change. The PF also requires a number of particles for accurate estimation, causing heavy computational burden. Therefore, it is difficult to use the PF for real applications. To overcome PF drawbacks, we propose the extended finite memory (EFM) filter and hybrid particle filtering algorithm combining the regularized particle filter (RPF) as the main filter with an auxiliary EFM filter. The hybrid particle/EFM filter can detect RPF failure and reset the particles using an EFM estimation. The proposed filter shows robust performance against severe signal noise and abrupt change of target motion. Experiments using vehicle radar signals were performed in harsh environments to compare the proposed tracker with current best practice regularized particle and extended Kalman trackers.

APPLICATION OF THE MATRIX PENCIL METHOD FOR RADAR MEASUREMENTS OF ELEVATION ANGLES OF LOW-ALTITUDE TARGETS OVER A DISTURBED SEA

The study is focused on the problem of improving the accuracy of radar measurements of elevation angles of low-altitude targets over a sea. The Matrix Pencil method, which relates to the high spectral resolution techniques, is investigated in the paper as one of the possible instruments for solving the problem. A number of studies analyze the possibility of applying the method for measuring radio wave angles of arrival. However, the extent of its usefulness for solving the problem of interest requires to be analyzed with account of specific conditions under which elevation angles of low-altitude targets are measured. The study was carried out by means of computer simulations. The analysis covered sea states responsible for the specular as well as for high diffuse reflections. One of the main tasks of the present paper was determining the extreme measurement accuracy achievable by the method on the conditions where the diffuse reflection from the sea is considered as interference (the specular reflected signal along with the direct signal from the target is considered as the measured signal). It is shown that the Matrix Pencil method does not yield to the MUSIC method in this characteristic but even surpasses it, especially in the case of high diffuse reflections, when the improvement riches 20%. Another important task was investigation of the influence of a priori parameters of the method, specifically, the number of the measured signals, value of the so-called pencil- parameter and number of the spatial samples of the signal across the specified antenna aperture, on the measurement error. Recommendations have been developed on the selection of these parameters that make it possible to minimize elevation angle measurement errors. The performed investigation expands our understanding about the ways of improving the accuracy of measuring elevation angles of low-altitude targets over a disturbed sea.

Modernization of the Irkutsk Incoherent Scatter Radar

We present the results of modernization of the Irkutsk Incoherent Scatter Radar’s control and acquisition system. The modernization was carried out using results of space experiments Plasma–Progress and Radar–Progress involving Progress cargo spacecraft. The modernization has improved the accuracy of radar measurements of low-orbit spacecraft. For example, with a signal-to-noise ratio equal to10, the accuracy of range and angle measurements is 100–300 m and 1–5 arc min.

Модернизация Иркутского радара некогерентного рассеяния

We present the results of modernization of the Irkutsk Incoherent Scatter Radar’s control and acquisition system. The modernization was carried out using results of space experiments “Plasma—Progress” and “Radar—Progress” involving Progress cargo spacecraft. The modernization has improved the accuracy of radar measurements of low-orbit spacecraft. For example, with a signal-to-noise ratio equal to10, the accuracy of range and angle measurements is 100–300 m and 1–5 arc min.

Radar measurement accuracy associated with target RCS fluctuation

Radar measurement accuracy is mainly dependent on the signal-to-noise ratio (SNR). SNR variation of the same target is related to fluctuating target radar cross-section (RCS) that is known as Swerling RCS model. Radar measurement accuracy is an important parameter to design a radar system or to analyse its performance. More useful measurement accuracy formula than the previous research that is sensitive to the detection threshold is proposed. To investigate the measurement accuracy affected by Swerling model, the relative standard deviation is defined to compare the value of the previous research with the proposed value.

RADAR ELEVATION ANGLES MEASUREMENTS OF LOW-ALTITUDE TARGETS OVER THE SEA BY ROOT-MUSIC METHOD UNDER INTERFERENCE FROM MULTIPATH AND THERMAL NOISE OF DIRECTION FINDER

The paper is related to improvement of the accuracy of radar measurements of the elevation angles of low-altitude targets above the sea using the root-MUSIC, which is considered by experts as one of the means to solve this problem. Unlike in previous studies, which take into account the multipath noise only, in this study the clutter is complicated by thermal noise of the direction finder. This allows evaluating the capabilities of the method and providing guidance on its application under the close to reality conditions. The study was carried out by computer simulation. It covered various sea roughness states at which the conditions from specula to strong diffuse reflection were complied. A wide range of signal-to-noise ratios was used during the simulation. The main focus was the study of effects on measurement errors of a priori parameters of the method: the signal subspace dimensionality and the order of autocorrelation matrix of the signals received by a multi-element antenna array. The recommendations of their choice, allowing minimization of errors of elevation measurement in different conditions, have been developed. The results of the study extend the knowledge of how to improve the methods for measuring the low-altitude target elevation angle above the sea.

Carrier Rocking Motion Model Based on Stress Analysis

The complicated sports of aircraft carrier affected by the wind and waves when sailing affects the measurement accuracy of shipboard radar seriously. In order to eliminate the effect of carrier motion to improve the accuracy of radar measurement, we must establish the motion model of aircraft carrier and research on the motion of carrier. At present there is not much research on movement of domestic aircraft carriers, and the overseas research are in a state secret. Established the motion model of aircraft carrier according to the force of carrier caused by wave. Provides help for the research on carrier motion law and influence on the accuracy of radar.

Simulation on the Track Integration of Radar System and ADS-B

The accuracy of radar measurement is an available data source to ads-b measure. Track fusion can make the aircraft track is more accurate, it is more significance to the accuracy of radar measurement. Through the establishment of ads-b and radar measurement equation, the algorithm is put forward, and verified the simulation and confirmed the feasibility of the algorithm.

Radar rainfall error variance and its impact on radar rainfall calibration

The high degree of uncertainty in radar rainfall estimation is caused by the variability in the vertical profile of reflectivity, the errors in measurements of radar reflectivity, conversion of reflectivity to rainfall rate, and the error of using point rain gauge rainfall in representing mean-areal rainfall of a radar grid size in the radar rainfall calibration. Presented here is an approach that explicitly takes into account the variations in reliability of radar rainfall estimates associated with range from the radar in calibrating of Z– R relationship. The reliability of radar rainfall estimates is calculated from the proposed climatological variance of radar rainfall error model that accounts for rainfall intensity, nature of rainfall event and number of pulses averaged in obtaining a reflectivity pixel value. Modifications to the parametric and probability matching methods (PMM) are proposed to account for the reliability of the radar rainfall estimates at the gauge locations. Six months of reflectivity-rain gauge data from the Kurnell radar in Sydney, Australia are used to test the model. The result shows the improvements in accuracy of radar measurements of rainfall by incorporating the reliability of radar rainfall estimates in the PMM are about 10% and 5% compared with the conventional PMM and parametric Z– R relationship method, respectively.

Rainfall Characteristics Associated with the Remnants of Tropical Storm Helene in Upstate South Carolina

Abstract A description is given of rainfall characteristics associated with the remnants of Tropical Storm Helene, which made landfall on the panhandle of Florida and moved through parts of Georgia, South Carolina, and North Carolina during 22–23 September 2000. Also included in the description are rainfall events in advance of the approach of Helene to South Carolina. Emphasis is placed on the implications of these characteristics regarding the ability of the Weather Surveillance Radar-1988 Doppler (WSR-88D) to measure rainfall accurately for this system when employing reflectivity factor–rainfall rate (Z–R) algorithms as defined by the National Weather Service. The results are based on analysis of raindrop size spectra collected with a disdrometer in upstate South Carolina at the Clemson University Atmospheric Research Laboratory. It was found that there were pronounced variations in the Z–R relationship from day to day and within a day that would limit the accuracy of radar measurement of rainfall. A d...

Developments in radar and remote-sensing methods for measuring and forecasting rainfall.

Over the last 25 years or so, weather-radar networks have become an integral part of operational meteorological observing systems. While measurements of rainfall made using radar systems have been used qualitatively by weather forecasters, and by some operational hydrologists, acceptance has been limited as a consequence of uncertainties in the quality of the data. Nevertheless, new algorithms for improving the accuracy of radar measurements of rainfall have been developed, including the potential to calibrate radars using the measurements of attenuation on microwave telecommunications links. Likewise, ways of assimilating these data into both meteorological and hydrological models are being developed. In this paper we review the current accuracy of radar estimates of rainfall, pointing out those approaches to the improvement of accuracy which are likely to be most successful operationally. Comment is made on the usefulness of satellite data for estimating rainfall in a flood-forecasting context. Finally, problems in coping with the error characteristics of all these data using both simple schemes and more complex four-dimensional variational analysis are being addressed, and are discussed briefly in this paper.

Experience of real time spatial adjustment of the Z-R relation according to water phase of hydrometeors

According to hydrometeor water phase analysis (rain, snow, sleet) an optimal relation between the radar reflectivity factor (Z) and precipitation intensity (R in rain, S in snowfall) is applied individually at each radar pixel in real time. Gauges are used to evaluate the improvement in radar accumulation. The results show that the phase dependent Z-R/S selection does not significantly improve the accuracy of radar measurements. Reflectivity profile effects and wind deflection in gauges are dominating error factors.

Use of a weather radar for the hydrology of a mountainous area. Part II: radar measurement validation

This paper investigates the validation of radar rainfall measurement in a mountainous region by comparison with raingage data. Initially, the comparison serves as a basis for defining the assessment factor introduced to correct the systematic bias often affecting radar data. Several methods are available for determining the assessment factor and all are shown to provide a similar result. Corrections for both beam blockage and vertical profile of reflectivity are also evaluated. Both corrections provide an improvement in radar measurement accuracy. The validation of radar rainfall measurement is performed at the catchment scale of a few hundred square kilometres and at an hourly time period, these conditions being consistent with hydrological needs. The reference rainfall is determined by interpolating data from a dense raingage network. The accuracy of the areal reference value is defined by its standard deviation. A validation criterion taking into account the accuracy of the reference value is introduced. Validation results show a good level of agreement between reference measurements and radar data at the catchment scale. The confidence associated with the reference value suggests a combined use of radar and raingages based on the control of radar estimates by raingage measurements. © 1997 Elsevier Science B.V.

Rainfall Estimation Using Polarimetric Techniques at C-Band Frequencies

Abstract The accuracy of radar measurements and their derived parameters, such as rainfall rate, are compromised by errors caused by propagation effects at C-band frequencies. The radar measurements of reflectivity factor Z and differential reflectivity ZDR are affected by the absolute and differential attenuation through the rain medium. Another useful radar-derived parameter, differential propagation phase shift ΦDP, is contaminated by the differential phase on backscatter δ, which attains significant values in rainfall at C-band frequencies. In this paper we present a technique to correct these propagation and backscatter effects by application of an algorithm that corrects first Z and ZDR, using relationships between the specific and differential attenuations versus phase shift, which is followed by estimation of the differential backscatter phase shift parameter δ from the corrected ZDR. Simulation results are presented to demonstrate the effectiveness of this correction procedure for two cases: (a) ...

Application of Kriging Method to Improvement of Accuracy of Radar Measurements

he application of radar rainfall measurements to hydrologic practices involves many difficulties in identifying radar constants B and β, and calibrating radar information via use of ground measurements and so forth. It is of practical importance to take into account the space scale difference for comparing radar measurements with ground information precisely.The present study converts ground point rainfalls to the average areal rainfall, using the Kriging method, and shows its effect on the identification of B and, β, and calibration.The Kriging method enables one to estimate the average rainfall over a given catchment area, quantify the accuracy of areal estimates, provide data input for auto-matic contouring and design the raingauge networks.

Application of Kriging Method to Improvement of Accuracy of Radar Measurements

The application of radar rainfall measurements to hydrologic practices involves many difficulties in identifying radar constants B and β, calibrating radar information via use of ground measurements and so forth. The currently used method compares radar areal rainfall directly with ground point rainfall in spite of the difference of space scale. It is of practical importance to develop a new method which can take into account the space sacle difference for comparing radar measurements with spatial ground information precisely.The present study converts ground point rainfall to average areal rainfall, using the Kriging method which enables one to estimate the average rainfall over a given catchment area, quantify the accuracy of areal estimates, provide data input for automatic contouring and design the raingauge networks.

Radar Receiver Transfer Function Estimate from Correlated Meteorological Echoes

Abstract The precise and continuous calibration of a radar is an important task for maintaining the accuracy of radar measurements. The calibration of radar receiver transfer function slope can be performed using bias measurements of meteorological echoes. The bias measurement is obtained as the difference in the estimate of the mean power given by a logarithmic receiver and a power law receiver. The estimate of the receiver transfer function slope (obtained from bias measurement) and its accuracy are studied in this paper, taking into consideration the correlation structure of the radar time samples. Using the asymptotic theory and computer simulation, the estimate of receiver transfer function slope and its variance are evaluated for many sample sizes and Doppler spectra. Verification of the theoretical results is presented using data collected by the Polar 55-C band radar in Italy.