Echo Location Research Articles

Application of SuperDARN Interferometry for Improved Estimates of Doppler Velocity and Echo Geolocation

AbstractIt has been previously established that the Doppler velocities of F‐region ionospheric echoes observed by the Super Dual Auroral Radar Network (SuperDARN) at high frequencies (HF, 8–20 MHz) are persistently lower than those measured by other instruments at the same locations. This was attributed to the ionospheric refractive index for HF radio waves being noticeably smaller than one. The refractive index values can be obtained in two ways: based on electron density estimates from a co‐located instrument or a model, or by deriving them from SuperDARN elevation angle data. To compare these methods, we considered line‐of‐sight Doppler velocity observations by the Rankin Inlet (RKN) SuperDARN radar and the Resolute Bay Incoherent Scatter Radars (RISR). The velocity data were supplemented by electron density measurements from RISR. The elevation angle data were also used for accurate determination of SuperDARN echo geolocation because the actual ground range to the echo location may significantly differ from that obtained with the conventional SuperDARN models. The RISR Doppler velocity values were used as a reference to the RKN observations via 0.5‐hop and 1.5‐hop propagation paths. Correction by the index of refraction based on both maximum electron density from the RISR and elevation angle data from RKN brought 0.5‐hop data close to the RISR velocity values, with the latter representing a self‐contained approach. However, for 1.5‐hop echoes from the polar cap, the uncorrected SuperDARN velocities exceeded those from RISR. We discuss potential causes of this apparent anomaly.

Echo Location: Distances to Galactic Supernovae From ASAS-SN Light Echoes and 3D Dust Maps

Light echoes occur when light from a luminous transient is scattered by dust back into our line of sight with a time delay due to the extra propagation distance. We introduce a novel approach to estimating the distance to a source by combining light echoes with recent three-dimensional dust maps. We identify light echoes from the historical supernovae Cassiopeia A and SN 1572 (Tycho) in nearly a decade of imaging from the All-Sky Automated Survey for Supernovae (ASAS-SN). Using these light echoes, we find distances of 3.6±0.1 kpc and 3.2−0.2+0.1 kpc to Cas A and Tycho, respectively, which are generally consistent with previous estimates but are more precise. These distance uncertainties are primarily dominated by the low distance resolution of the 3D dust maps, which will likely improve in the future. The candidate single degenerate explosion donor stars B and G in Tycho are clearly foreground stars. Finally, the inferred reddening towards each SN agrees well with the intervening column density estimates from X-ray analyses of the remnants.

Functional performance comparison of long cane and secondary electronic travel aids for mobility enhancement

This study investigated the impact of secondary electronic travel aids (ETAs) on the mobility performance of individuals with profound visual impairment, specifically focusing on object detection and obstacle avoidance tasks. Seven experienced long-cane users were recruited for the study. The ETAs tested as secondary aids to the long cane included the MiniGuide, utilizing ultrasonic echo location, and the vOICe (Vision-to-Auditory Sensory Substitution Device), which translates visual information into auditory signals. Two software modes of the vOICe were examined: the standard contrast mode and a novel algorithm utilizing relative depth information. Notably, 30 min of familiarization was provided before the trials. Results indicated that while the use of the secondary ETAs led to increased awareness of the surrounding environment, it also resulted in longer processing times and more hesitations, compared with using the long cane alone. Participants demonstrated improved object detection and larger detection and safety ranges during obstacle avoidance. The study also introduced the concept of margin of stability (MoS) as a novel metric for evaluating gait stability while using ETAs. Both MiniGuide and vOICe users exhibited consistent and stable movements, suggesting that these additional aids did not negatively impact overall gait stability. The findings highlight the trade-offs between efficiency and effectiveness when using secondary mobility aids, with longer training periods potentially mitigating these issues. In addition, the study emphasizes the need for ongoing research to optimize the design and training programmes for new ETAs. Future studies may explore the impact of extended training periods on mobility performance. Overall, this research contributes to a deeper understanding of how ETAs can enhance the mobility of individuals with visual impairments while also highlighting some of the challenges associated with their use. Optimizing ETA design and training programmes is crucial for maximizing benefits for individuals with impaired vision.

Implementation of sprinkling location with restructure-monochrome-dot on diffusivity mutational-status of fabricated function agent on porous

The recognition technology that determines the sprinkling mutation status in simple squamous epithelium cells produces a monochromatic dot pattern in an echo state using the instantaneous recognition rate (MPR) and vacuum recognition rate (VPR). The diffusivity echo system was created in the form of sprinkler recognition to control recognition rate conditions. The mutation status of simple squamous epithelium cells is displayed as a sprinkling porous value according to the sprinkling location layer by a diffusivity-down structure to search as a jagged monochrome-dot pattern. In the sprinkling porous, the perception rate concept is verified by referencing the instantaneous rate and vacuum rate to the mutant state signal through the sprinkling echo conformation. The jagged mutation state of MPR-VPR appears from a sprinkling porous to a maximum-minimum sprinkling-echo conformation. Sprinkling echo locations are found in the sprinkling porous values of the mutant state. Wr-af-FA-τMED is far mutational-status of 18.12±5.16 units, Wr-af-CO-τMED is convenient mutational-status of 6.89±0.30 units, Wr-af-FL-τMED is flank mutational-status of 2.34±1.53 units, Wr-af-VI-τMED is vicinage mutational-status of 0.48±0.20 units. Diffusivity echo calculates the jagged momentary vacuum conformation that appears through the perception rate system in simple squamous epithelium cells, and the ability to estimate the sprinkling-echo conformation for the jagged degree perception rate of MPR-VPR can be confirmed. We can estimate the shape through the vacuum signal in the sprinkling porous and estimate the diffusion data of the diffusivity echo rate through the diffusivity perception system.

An Ultrasonic RF Acquisition System for Plant Stems Based on Labview Double Layer Multiple Triggering.

Ultrasound is widely used in medical and engineering inspections due to its non-destructive and easy-to-use characteristics. However, the complex internal structure of plant stems presents challenges for ultrasound testing. The density and thickness differences in various types of stems can cause different attenuation of ultrasonic signal propagation and the formation of different echo locations. To detect structural changes in plant stems, it is crucial to acquire complete ultrasonic echo RF signals. However, there is currently no dedicated ultrasonic RF detection equipment for plant stems, and some ultrasonic acquisition equipment has limited memory capacity that cannot store a complete echo signal. To address this problem, this paper proposes a double-layer multiple-timing trigger method, which can store multiple trigger sampling memories to meet the sampling needs of different plant stems with different ultrasonic echo locations. The method was tested in experiments and found to be effective in acquiring complete ultrasonic RF echo signals for plant stems. This approach has practical significance for the ultrasonic detection of plant stems.

Development and study of ultrasonic immersion testing system for industrial and metrological application

Ultrasonic non-destructive testing (NDT) is one of the prominent field involving inspection to evaluate defects, cracks, deposition or fusion of welding materials and dimensional measurements of the test piece(s). Ultrasonic immersion scanning systems are useful for various industrial and metrological applications. The conventional immersion system uses a dedicated pulser receiver module for the excitation and detection of signal from transducer and a fast analog data acquisition card (DAQ) to acquire the raw data into computer. Rigorous digital signal processing and filtering is used to extract desired information from the raw data. In the present work, development of an ultrasonic immersion C-scan testing system, intended for industrial and metrological applications, is described. The developed system uses a commercial ultrasonic flaw detector (UFD) for the data acquisition rather than using pulser receiver and DAQ card to acquire ultrasonic information. The software for the same has been developed in Visual Basic .NET framework to control all five servo motor based axes of the ultrasonic immersion scanning tank. The developed software scans the sample automatically with parameters specified by the user. The parameters include echo amplitude, echo location, separation between two echoes, and ultrasonic attenuation. The developed software generates the data files that can later be used for further analysis using suitable data analysis software such as Origin or MS excel. The functionality of the developed system has been tested for the detection of flaws present in the material, testing for thickness variation and ultrasonic attenuation. The developed system is capable of detecting the location of defects within the resolution of ±0.01 mm. Ultrasonic transducer movement resolution of ±0.01 mm over the sample, results in to generation of a high quality image.

Characterization of Nadir Echoes in Multiple-Elevation-Beam SAR With Constant and Variable Pulse Repetition Interval

Multiple-elevation-beam synthetic aperture radar (SAR) is a concept based on digital beamforming (DBF) in elevation and simultaneous recording of the echoes of multiple transmitted pulses. It enables high-resolution imaging of wide areas and is therefore ideal for the systematic observation of dynamic processes on the Earth’s surface. Furthermore, if the pulse repetition interval (PRI) is continuously varied (staggered SAR), it is possible to map a wide continuous swath rather than multiple subswaths separated by “blind” ranges. Within the design of multiple-elevation-beam SAR, however, it is fundamental to consider how nadir echoes affect the mapping capabilities of systems with constant PRI and the image quality of staggered SAR systems, where nadir echoes are intrinsically smeared due to the PRI variation. This article addresses the characterization of nadir echoes in multiple-elevation-beam SAR with constant and variable PRI by presenting a parametric model for the nadir echo profile based on real radar measurements, a formulation of the nadir echo location and smearing in staggered SAR, and realistic simulations based on TerraSAR-X data, which show that nadir echo are likely to be barely visible in staggered SAR images. The results of this work are relevant to both the design of future SAR systems and the interpretation of the acquired data.

Echo Location Based Bat Algorithm for Energy Efficient WSN Routing

Due to the wide range of applications, Wireless Sensor Networks (WSN) are increased in day to day life and becomes popular. WSN has marked its importance in both practical and research domains. Energy is the most significant resource, the important challenge in WSN is to extend its lifetime. The energy reduction is a key to extend the network's lifetime. Clustering of sensor nodes is one of the well-known and proved methods for achieving scalable and energy conserving WSN. In this paper, an energy efficient protocol is proposed using metaheuristic Echo location-based BAT algorithm (ECHO-BAT). ECHO-BAT works in two stages. First Stage clusters the sensor nodes and identifies tentative Cluster Head (CH) along with the entropy value using BAT algorithm. The second stage aims to find the nodes if any, with high residual energy within each cluster. CHs will be replaced by the member node with high residual energy with an objective to choose the CH with high energy to prolong the network's lifetime. The performance of the proposed work is compared with Low-Energy Adaptive Clustering Hierarchy (LEACH), Power-Efficient Zoning Clustering Algorithm (PEZCA) and Chaotic Firefly Algorithm CH (CFACH) in terms of lifetime of network, death of first nodes, death of 125th node, death of the last node, network throughput and execution time. Simulation results show that ECHO-BAT outperforms the other methods in all the considered measures. The overall delivery ratio has also significantly optimized and improved by approximately 8%, proving the proposed approach to be an energy efficient WSN.

Detection and segmentation of underwater CW-like signals in spectrum image under strong noise background

Aiming at the detection and segmentation of underwater Continuous wave-like (CW-like) signals of under strong noise sea background, this paper introduces a Gaussian mixture model clustering method by analyzing the signal spectrum features. First, the time domain original signal is converted to its frequency domain correspondence by Windowed Fast Fourier Transform. Second, by studying on the feature of target signal, we introduce a spectrum filtering to alleviate the background noise of ocean environment, which is analyzed and calculated with both time and frequency information. Then, the target echo location signals is constructed using a Gaussian mixture mode based binary clustering algorithm. Finally, we use the EM algorithm and adaptive binarization for solving and optimizing the clustering results. Experimental results have shown the accuracy and efficiency of our detection, which can be also simply modified and applied for detecting similar and specific signal from complex background noise.

Novel BAT Algorithm for Position Estimation of A GPS Receiver Located in Coastal Region of Southern India

Based on the echo location principle used by bats, the Bat Algorithm (BA) has been developed. By introducing foraging of bats and doppler effect in the Bat Algorithm leads to generate Novel Bat Algorithm (NBA). In this paper, the NBA is implemented to estimate the position of a GPS receiver located in the coastal area of Southern India. The estimated results are compared with the original survey coordinates of the GPS receiver. The result shows that the Novel Bat Algorithm is a better metaheuristic bio-evolutionary algorithm for GPS receiver position estimation. This algorithm can be useful to apply in RADAR, SONAR, and Indian Regional Navigational Satellite System (IRNSS) for Navigation, Tracking, and Positioning.

A nowcasting technique based on application of the particle filter blending algorithm

To improve the accuracy of nowcasting, a new extrapolation technique called particle filter blending was configured in this study and applied to experimental nowcasting. Radar echo extrapolation was performed by using the radar mosaic at an altitude of 2.5 km obtained from the radar images of 12 S-band radars in Guangdong Province, China. The first bilateral filter was applied in the quality control of the radar data; an optical flow method based on the Lucas–Kanade algorithm and the Harris corner detection algorithm were used to track radar echoes and retrieve the echo motion vectors; then, the motion vectors were blended with the particle filter blending algorithm to estimate the optimal motion vector of the true echo motions; finally, semi-Lagrangian extrapolation was used for radar echo extrapolation based on the obtained motion vector field. A comparative study of the extrapolated forecasts of four precipitation events in 2016 in Guangdong was conducted. The results indicate that the particle filter blending algorithm could realistically reproduce the spatial pattern, echo intensity, and echo location at 30- and 60-min forecast lead times. The forecasts agreed well with observations, and the results were of operational significance. Quantitative evaluation of the forecasts indicates that the particle filter blending algorithm performed better than the cross-correlation method and the optical flow method. Therefore, the particle filter blending method is proved to be superior to the traditional forecasting methods and it can be used to enhance the ability of nowcasting in operational weather forecasts.

Decomposition of small-footprint full waveform LiDAR data based on generalized Gaussian model and grouping LM optimization

Full waveform airborne Light Detection And Ranging(LiDAR) data contains abundant information which may overcome some deficiencies of discrete LiDAR point cloud data provided by conventional LiDAR systems. Processing full waveform data to extract more information than coordinate values alone is of great significance for potential applications. The Levenberg–Marquardt (LM) algorithm is a traditional method used to estimate parameters of a Gaussian model when Gaussian decomposition of full waveform LiDAR data is performed. This paper employs the generalized Gaussian mixture function to fit a waveform, and proposes using the grouping LM algorithm to optimize the parameters of the function. It is shown that the grouping LM algorithm overcomes the common drawbacks which arise from the conventional LM for parameter optimization, such as the final results being influenced by the initial parameters, possible algorithm interruption caused by non-numerical elements that occurred in the Jacobian matrix, etc. The precision of the point cloud generated by the grouping LM is evaluated by comparing it with those provided by the LiDAR system and those generated by the conventional LM. Results from both simulation and real data show that the proposed algorithm can generate a higher-quality point cloud, in terms of point density and precision, and can extract other information, such as echo location, pulse width, etc., more precisely as well.

Echolocation systems of leaf-nosed bats in Taiwan and Iriomote island, Japan

The leaf-nosed bats, Hipposideridae, are one of the most common tropical bats found in Asia. Two species of leaf-nosed bats in Iriomote island, Hepposideros turpis, and Taiwan, Hipposideros terasensis, were compared. They emit short echo location pulses (4-7 ms in duration) consisted of constant frequency (CF) component followed by downward frequency modulated (FM) component. The second harmonics are the most intense frequency component. Comparison lists for two species are shown below. Taiwanese leaf-nosed bats, Hipposiderous terasensis CF2: 70 kHz (CF1: 35 kHz) 50-60 g in weight Japanese leaf-nosed bats, Hepposideros turpis CF2: 82 kHz (CF1: 41 kHz) 20-30 g in weight threatened species (Red list). Both Taiwan and Iriomote island are at around the same North latitude 25 degrees. Findings from H. terasensis and H. turpis are introduced and discussed. [Research supported by MEXT, Japan, and Shandong University, China.]

Surface Clutter and Echo Location Analysis for the Interpretation of SHARAD Data From Mars

This letter presents a suite of analysis techniques designed to support the interpretation of data from the Shallow Radar on Mars Reconnaissance Orbiter. Cross-track surface echoes (“clutter”) with a time delay similar to potential subsurface echoes are known to present a major challenge to orbital radar sounding; furthermore, we demonstrate that the broad beam pattern of orbital sounders combined with cross-track long-wavelength surface slopes can result in first-received echoes arising from locations significantly distant from the nadir point, further hindering interpretation. Combining known surface topography (of lower resolution than the radar wavelength) with an appropriate radar model and orbital parameters, we can simultaneously address both of these challenges. Our technique has been applied to a variety of scientific targets on Mars with success and is recommended as a standard practice.

Comparative estimation of the diagnostic value of radiographic and ultrasound studies in microbial inflammatory diseases of the urinary tract in children

The results of using three imaging technologies (intravenous urography, micturating cystography, and B-mode kidney ultrasound imaging) in 62 children aged 10 to 206 months, examined at the city nephrology hospital, were comparatively analyzed. The findings showed the comparatively high diagnostic value (a sensitivity of 70% and a specificity of 87%) of echography particularly for severe urinary tract malformations. At the same time, echo location was found to be insufficient to detect vesicoureteral reflux (a sensitivity of 20% and a specificity of 85,5%), which is a ground for the further improvement of examination protocols for patients with urinary tract infections.

Plane Localization for MIMO Radar

We consider the problem of localizing a ground plane with respect to a multiple-input multiple-output (MIMO) radar within a three-dimensional environment. An example application is a low-visibility landing radar as described by Longstaff (“MIMO radar developments at Teledyne Australia,” Proc. Int. Conf. Radar, 2013). We propose an extension to the common tangent algorithm (COTA), which has been developed by the echo location community for localizing planes with single input multiple output (SIMO) audio systems. The method adopted for this paper is to generalize COTA for the multiple transmitters of the MIMO radar case. Generalizing the COTA equations generates a Non-Convex Quadratically Constrained Quadratic Program (NC-QCQP). We show that by first replacing the quadratic constraints by linear approximations we can solve the NC-QCQP problem by iteratively solving a series of quadratic programming problems. This method demonstrates both global convergence and convergence to the Cramer-Rao Lower Bound (CRLB). We then extend this approach to additionally linearize the quadratic objective function, which in turn reduces the iterate to a simple pseudoinverse. This method retains the global convergence properties of the previous method, but does not quite converge to the CRLB. We also investigate two methods which operate directly on the unconstrained cost function, the first a Newton–Raphson based method and the second a singular value decomposition (SVD)-based approach to solving the optimization problem. The SVD method exhibits approximately quadratic convergence and reaches the CRLB. However, it is only locally convergent. The Newton–Raphson method also achieves the CRLB. We use numerical simulations to demonstrate the validity of the techniques presented and show a comparison to the CRLB for the plane localization problem. Finally, we discuss a preprocessing technique that can be used to improve the estimation accuracy. We conclude by demonstrating the proposed algorithms on data collected from the low visibility landing aid radar (Longstaff , 2013) developed at Teledyne Defence Australia.

A comparative study of BA, APSO, GSA, hybrid PSOGSA and SPSO in dual channel speech enhancement

The present paper focuses on the suppression of background noise in speech signal by utilizing a powerful heuristic optimization algorithm called Bat algorithm (BA) for adaptive filtering in dual channel enhancement systems. Bat algorithm is a recently developed population based meta heuristic approach which is inspired by the hunting behavior of the bats. It is developed by Yang (2010). As a novel feature Bat algorithm is based on the echo location behavior of micro bats. BA uses the frequency tuning technique to increase the diversity of the solutions in the population, while at the same time it uses the automatic zooming and tries to balance the exploration and exploitation. A few studies have been carried out on the use of heuristics for ANC in speech enhancement by using standard particle swarm optimization (SPSO) and some of its variants till 2010. In order to extend these heuristic approaches to speech, accelerated particle swarm optimization (APSO) based enhancement approach has been proposed (Prajna et al. in Int J Speech Technol 17(4):341---351, 2014a; Prajna et al. in IJISA 6(4):1---10, 2014b, doi:10.5815/ijisa.2014.04.01; Prajna et al. in IEEE international conference on communications and signal processing (ICCSP), April 2014, pp 1457---1461, 2014c, doi:10.1109/ICCSP.2014.6950090). To overcome the problem of poor exploitation ability of APSO, another approach is proposed based on gravitational search algorithm (GSA) (Prajna et al. 2014a, b, c). To combine both the abilities of PSO and GSA algorithms, Hybrid PSOGSA algorithm is also proposed to ANC (Prajna et al. 2014a, b, c). To further improve the efficiency of adaptive filtering in ANC, by providing a dynamic balance between exploration and exploitation, BA is proposed to speech enhancement. This paper intends to present the Bat algorithm as an improved approach to ANC in speech enhancement when compared with that of SPSO, APSO, GSA and Hybrid PSOGSA based speech enhancement algorithms. The performance of all the algorithms is evaluated by computing four objective measures SNRI, PESQ, FAI and WSS, in two real world noise conditions Babble and Factory, at three different input SNR levels set at ?10, 0 and 5 dB. Simulation results prove that BA is the most successful algorithm of all the algorithms studied in this work, to suppress the background noise more effectively.

Full correction for spatially distributed speed-of-sound in echo ultrasound based on measuring aberration delays via transmit beam steering

Aberrations of the acoustic wave front, caused by spatial variations of the speed-of-sound, are a main limiting factor to the diagnostic power of medical ultrasound imaging. If not accounted for, aberrations result in low resolution and increased side lobe level, over all reducing contrast in deep tissue imaging. Various techniques have been proposed for quantifying aberrations by analysing the arrival time of coherent echoes from so-called guide stars or beacons. In situations where a guide star is missing, aperture-based techniques may give ambiguous results. Moreover, they are conceptually focused on aberrators that can be approximated as a phase screen in front of the probe. We propose a novel technique, where the effect of aberration is detected in the reconstructed image as opposed to the aperture data. The varying local echo phase when changing the transmit beam steering angle directly reflects the varying arrival time of the transmit wave front. This allows sensing the angle-dependent aberration delay in a spatially resolved way, and thus aberration correction for a spatially distributed volume aberrator. In phantoms containing a cylindrical aberrator, we achieved location-independent diffraction-limited resolution as well as accurate display of echo location based on reconstructing the speed-of-sound spatially resolved. First successful volunteer results confirm the clinical potential of the proposed technique.

Sound speed structure monitoring of the Antarctic Ocean by new style float

JAMSTEC developed the new profiling float “Deep NINJA” for deep-sea type, was subjected to long-term monitoring of one year in the Antarctic Ocean off the coast of Adelie Coast from 2012. As a result, succeeded in the long-term monitoring of the sound speed profile to depth of the 4000 m in the Antarctic Ocean for the first time in the world, and was able to capture a seasonal change in the surface area in the freezing season and the thawing season. In addition, calculating a sound speed from these data, simulations were performed assuming the low frequency sonar. The result was obtained, the ingredient which propagates while repeating a reflection in the extremely small layer of the sea surface neighborhood, and the ingredient that propagates while being reflected in near the water depth 100m which changes of sound speed gradient. From this, propagation loss was small in winter than summer, and was shown a possibility that a sound wave would propagate to a more distant place. This may affect the long-distance sound wave propagation of the echo locations of the passive sonar and marine mammals.

Neglect of bandwidth of Odontocetes echo location clicks biases propagation loss and single hydrophone population estimates

Passive acoustic monitoring with a single hydrophone has been suggested as a cost-effective method to monitor population density of echolocating marine mammals, by estimating the distance at which the hydrophone is able to intercept the echolocation clicks and distinguish these from the background. To avoid a bias in the estimated population density, this method relies on an unbiased estimate of the detection range and therefore of the propagation loss (PL). When applying this method, it is common practice to estimate PL at the center frequency of a broadband echolocation click and to assume this narrowband PL applies also to the broadband click. For a typical situation this narrowband approximation overestimates PL, underestimates the detection range and consequently overestimates the population density by an amount that for fixed center frequency increases with increasing pulse bandwidth and sonar figure of merit.