Bearings-Only Target Motion Analysis using Ray Tracing

Bearing and frequency measurements of TMA (Target Motion Analysis) in passive line array SONAR have lower bearing rate and frequency doppler, and are not detected or tracked continuously because of various ocean environments. This is a main reason to effect the TMA performance and it takes a long time to get TMA solutions. We propose the bearing and frequency TMA(BFTMA) using accumulative batch estimation to solve the TMA problem of line array passive SONAR. The accumulative batch estimation structure is based on MLE (Maximum Likelihood Estimation) but used accumulative measurements. The accumulative batch estimation is applied for the BFTMA with nonlinear Kalman filter to estimate the target range, speed and course. Simulation and sea data analysis were carried out to verify the performance and applicability of the proposed techniques.

In bearings-only target motion analysis (BOTMA), the common hypothesis is that the observer maneuvers while the source is traveling according to a constant speed and course. But there is no reason that the roles of each protagonist cannot be exchanged. In this paper, we consider an uncommon scenario: the trajectory of the target is composed of two legs (i.e., a target brutally changes its heading while keeping its speed) and the observer does not maneuver. We prove that the trajectory of the target is observable under nonrestrictive conditions. A batch estimator is proposed, and its performance is compared with the classic Cramer-Rao lower bound (CRLB). Monte-Carlo simulations reveal the efficiency of the estimator. The robustness to a nonbrutal heading change is evaluated. Then an adhoc estimate taking the correct model into account is proposed and applied to simulated data. Again, its performance is compared with the CRLB, and its robustness is evaluated when the speed of the target changes. Finally, the respective performances of the target motion analysis (TMA) made by each mobile are compared.

A new algorithm for 2-D DOA estimation

The IRNSS satellite network covers a large area of the India with 7 satellites, 3 geostationary and 4 that are geosynchronous.IRNSS signals are transmitted in the L5 and S-Bands.The L5 band frequencies range from 1164.45-1188.45MHz and the S band frequencies range of 2483.5-2500MHz.NavIC is the IRNSS satellite constellation network that can be employed to a variety of applications.The paper shows the analysis of the azimuth and elevation angle with respect to carrier to noise ratio.This study will be stepping stone for the collection of data using reflectometry.The different graphs were obtained and analyzed.Satellite tool kit is also used for the analysis of the elevation and azimuth angle.

Spatial vectorcardiogram in acute inferior wall myocardial infarction: its utility in identification of patients prone to complete heart block

The observability for bearings-only target motion analysis is a very important problem. The bearings-only system is to be said observable if and only if the target motion parameters can be uniquely determined by noise-free bearing measurements. The problem of unobservability for hearing-only target tracking system is discussed in this paper based on the target that travels in the 2-dimentional space with a constant acceleration. Utilizing Gramm rule and rank of matrix, a new proposition that the bearing-only locating and tracking system remains unsolvable prior to an observer maneuver is presented and proved. By proving the proposition, it is shown that for certain type of observer movement the estimation process remains unobservable, even if the target moves with a constant accelerate. The work done in this paper is a valuable study in solving the bearings-only target motion analysis.

Shoulder joint position sense improves with elevation angle in a novel, unconstrained task

Experimental investigation of peak wind loads on tandem operating heliostats within an atmospheric boundary layer

To reduce the gas disaster of high gas coal seam and improve the efficiency of gas extraction by high drilling, the layout parameters of drilling holes in Pingdingshan coal mine are optimized. Based on the analysis and calculation of the "three zones" of the movement towards the overly strata of No.10 coal in Pingdingshan coal mine, the height of caving zone and fissure zone in 24,130 working face are 10.06–14.46 m and 38.75–49.95 m respectively. The elevation angle, azimuth angle and the length of high-level boreholes are studied and analyzed by COMSOL numerical simulation software. The simulation results show that the optimum layout parameters of high-level boreholes are as follows: The elevation angle of borehole should be controlled at 9°–12°, the azimuth angle should be 30°–45°, and the length of borehole should be 150 m. Then the optimum layout parameters of high-level boreholes are determined for engineering application of 24,130 working face. Borehole data onto actual mine show that the optimum layout parameters of high-level boreholes were elevation angle between 8°and 11°, azimuth angle between 30° and 42°, and length of boreholes between 145 and 155 m. The simulation results are basically consistent with the measured data. The maximum gas concentration in working face, upper corner and return air roadway is stably controlled below 1%. The safe mining of 24,130 working face is ensured, which provided a certain reference value of gas control in the goaf of Pingdingshan mine and adjacent mines.

When wireless electromagnetic waves pass through the earth's atmosphere, they are affected by ionospheric irregularities, and their amplitude and phase will jitter rapidly in a short period of time, which is called ionospheric scintillation. With the human exploration of outer space and the demand for space communication, the study of ionospheric scintillation characteristics and its influence on electromagnetic communication has become increasingly important. This paper used the observation data received by GPS scintillation/TEC receivers in the Chengdu (104.07° N, 30.67° E) area of China from January 2018 to September 2020, and a data processing program was developed for the received GPS/BDS/GAL. The satellite data at multiple frequency points were processed to extract key data such as S4, azimuth angle, and elevation angle, and then the annual changes in ionospheric scintillation in the Chengdu region and the characteristics of local time changes were statistically analysed. The results show that the frequency and intensity of ionospheric scintillation events have obvious half-year changes. The scintillation intensity and frequency in spring and autumn are higher and more frequent than those in summer and winter; and scintillation events mainly occur at night. but they also occur during the day, mostly in the afternoon; and their occurrence is related to the airspace and is further closely related to the elevation and azimuth angles of the observation point. The overall scintillation events from 2018 to 2020 were in a gradual downward trend. At the end of May 2018, a scintillation event with a longer duration occurred. Further analysis showed that the occurrence of scintillation events increased with the rapid changes in solar activity and the geomagnetic environment. There is a certain positive correlation between the changes.

This experimental study outlines a method to calculate the design wind loads on heliostats, based on peak wind load coefficients reported in the heliostat literature and aerodynamic shape factors derived from high-frequency pressure measurements on an isolated heliostat at different elevation and azimuth angles in a boundary layer wind tunnel. The results show that the aerodynamic shape factors are largest for a range of heliostat configurations, including elevation angles of 15°, 30° and 45°and azimuth angles of 0° and 45°. The distribution of shape factors indicates that the leading edge of the heliostat is most vulnerable to wind-induced mirror damage in this range of critical elevation angles for heliostat design wind loads. The method proposed in the current study for heliostats conforms to the procedure used in design wind codes and standards for buildings and roof-mounted solar panels.

Multipath effects are the most challenging error sources for the Global Navigation Satellite System receiver, affecting observation quality and positioning accuracy. Due to the non-linear and time-varying nature, multipath error is difficult to process. Previous studies used a homogeneous indicator to characterize multipath effects and only revealed the temporal or spatial correlations of the multipath, resulting in limited correction performance. In this study, we consider the code multipath to be influenced not only by the elevation and azimuth angle of certain stations to satellites but also to be related to satellite characteristics such as nadir angle. Hence, azimuth angle, elevation angle, nadir angle and carrier-to-noise power density ratio are taken as multiple indicators to characterize the multipath significantly. Then, we propose an Attention-based Convolutional Long Short-Term Memory (AT-Conv-LSTM) that fully exploits the spatiotemporal correlations of multipath derived from multiple indicators. The main processing procedures using AT-Conv-LSTM are given. Finally, the AT-Conv-LSTM is applied to a station for 16 consecutive days to verify the multipath mitigation effectiveness. Compared with sidereal filtering, multipath hemispherical map (MHM) and trend-surface analysis-based MHM, the experimental results show that using AT-Conv-LSTM can decrease the root mean square error and mean absolute error values of the multipath error more than 60% and 13%, respectively. The proposed method can correct the code multipath to centimeter level, which is one order of magnitude lower than the uncorrected code multipath. Therefore, the proposed AT-Conv-LSTM network could be used as a powerful alternative tool to realize multipath reduction and will be of wide practical value in the fields of standard and high-precision positioning services.

<strong class="journal-contentHeaderColor">Abstract.</strong> When wireless electromagnetic waves pass through the earth's atmosphere, they are affected by ionospheric irregularities, and their amplitude and phase will jitter rapidly in a short period of time, which is called ionospheric scintillation. With the human exploration of outer space and the demand for space communication, the study of ionospheric scintillation characteristics and its influence on electromagnetic communication has become increasingly important. This paper used the observation data received by GPS scintillation/TEC receivers in the Chengdu (104.07°&thinsp;N, 30.67°&thinsp;E) area of China from January 2018 to September 2020, and a data processing program was developed for the received GPS/BDS/GAL. The satellite data at multiple frequency points were processed to extract key data such as S4, azimuth angle, and elevation angle, and then the annual changes in ionospheric scintillation in the Chengdu region and the characteristics of local time changes were statistically analysed. The results show that the frequency and intensity of ionospheric scintillation events have obvious half-year changes. The scintillation intensity and frequency in spring and autumn are higher and more frequent than those in summer and winter; and scintillation events mainly occur at night. but they also occur during the day, mostly in the afternoon; and their occurrence is related to the airspace and is further closely related to the elevation and azimuth angles of the observation point. The overall scintillation events from 2018 to 2020 were in a gradual downward trend. At the end of May 2018, a scintillation event with a longer duration occurred. Further analysis showed that the occurrence of scintillation events increased with the rapid changes in solar activity and the geomagnetic environment. There is a certain positive correlation between the changes.

A sparse planar array vertically placed in y–z plane is proposed to improve the angle estimation accuracy of sources in low angle region with reflection multipath. With two sizes of spatial invariances along both dimensions, the array estimates the azimuth and elevation angles using unitary ESPRIT (estimation of signal parameters via rotational invariance techniques). The first spatial invariance with a displacement of half-wavelength yields unambiguous coarse estimates of high-variance, while the second spatial invariance with much larger a displacement of subarrays obtains cyclically ambiguous fine estimates of low-variance. The final estimates are obtained by disambiguating fine estimates with coarse estimates. A novel pairing scheme is proposed to pair both the azimuth and elevation, coarse and fine angle estimates of the same signal. In addition, a new method is presented to calculate 2D angles, which substitutes the estimated elevation angle into the sin relative to the y-axis to get the azimuth angle. Employing real-valued processing and array aperture extension, the new DOA measuring method de-correlates the multipath signals and enhances angle resolution with no extra antennas and computational complexity. Simulation results show the effectiveness of the proposed technique and its advantages over the conventional methods.

Neural networks have been applied very successfully in the identification and control of nonlinear dynamic systems. The paper presents a design of neural network based control system for 2DOF nonlinear laboratory helicopter model (Humusoft CE 150). The main objective of this paper is to develop artificial neural networks to control helicopter's motors, or consequently elevation and azimuth angles. Neural networks are obtained by cloning various type of controllers designed in our previous papers. Those procedures included a cloning linear PID controller, gain scheduling controller and fuzzy controller.