Elevation Angle Research Articles

Validation of Two Newly Developed Albedo Schemes Based on the Observations Over the Region With Evergreen Broadleaved Forest in Southern China

AbstractExisting land surface models still have large error in the simulation of surface albedo. At present, introducing the influence of meteorological factors into the albedo parameterization scheme is an effective way to improve the albedo simulation. However, the improvement of the vegetation canopy surface albedo parameterization scheme is still insufficient. Therefore, based on the radiation and meteorological observation data during 1 November 2015–30 April 2018 from a land‐atmosphere interaction observation tower in a typical secondary evergreen broadleaved forest in Southern China, this study firstly analyzed the influencing factors of canopy surface albedo. It was found that the solar elevation angle and air relative humidity are two key factors influencing the canopy surface albedo, and the impact of the solar elevation angle on canopy surface albedo is not exactly the same on diurnal and seasonal scales. Then, two new canopy surface albedo parameterization schemes of additive form and multiplicative form were proposed and introduced into CLM5 model for single point simulation. Results show that the adoption of newly developed canopy surface albedo parameterization schemes can improve the simulation of diurnal and seasonal variations of albedo and reduce the overestimation of the simulation of near‐infrared radiation albedo and visible radiation albedo in the CLM5 model, then significantly reduce the root mean square errors of reflected solar radiation and net radiation simulation.

Characterization of BDS Multipath Effect Based on AT-Conv-LSTM Network

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.

Implementation of large angle low error non-line-of-sight ultraviolet communication system

Due to the strong scattering of ultraviolet (UV) communication, it is particularly suitable for scenarios involving short distance and large angle scattering, such as communication between buildings and jungles. In this paper, a system based on a single scattering model and a discrete Poisson channel pulse counting signal processing algorithm is constructed, and the effects of the number of signal photons, noise photons, and elevation angle on the system's bit error rate (BER) are simulated and analyzed. The effect of sampling rate on the system's performance is numerically analyzed. The results show that the pulse counting algorithm is suitable for systems with a small number of signal photons and a high sampling rate. The BER of the system when the number of signal photons becomes large is more dependent on the sampling rate than the signal-to-noise ratio. Additionally, we designed an outdoor test system including hardware system, pulse counting, synchronization and data recovery algorithms. The test results are consistent with the simulation results. The communication rate of the outdoor system is designed to be 10 kbps at a distance of 50 m. The BER is 10-3 when the elevation angle is 85°, while the BER is 10-5 when the elevation angle is 50°.

Troposphere Sensing Using Grazing‐Angle GNSS‐R Measurement From LEO Satellites

AbstractThis paper studies a new concept of using global navigation satellite system (GNSS) signals coherently reflected over relatively smooth ocean and ice surfaces from very low elevation angles (below ∼8°) and received by low Earth orbit (LEO) satellites to retrieve the tropospheric information. This approach can provide horizontal profiles of tropospheric zenith delay and total column water vapor (TCWV) with centimeter‐level high precision and spatial resolutions of tens of km by ∼1 km, depending on the elevation angle, with a sampling spacing of ∼100 m. This approach can potentially be applied to most sea ice and calm ocean areas and provide tropospheric sensing data, which can complement and augment existing observation systems. A few case studies are conducted in this paper using the Spire grazing‐angle GNSS‐R data. The retrieved TCWV is compared to ERA5 products and the Sentinel‐3 Ocean and Land Color Instrument measurements and shows promising performances. The errors associated with the GNSS‐R tropospheric measurements are also discussed.

Significant Location Accuracy Changes Resulting from Lightning Detection Networks Deployed on Inclined Terrains

This study investigates the location accuracy distribution of the lightning detection networks (LDNs) deployed on inclined terrains, an aspect frequently encountered in complex terrains but hitherto disregarded in previous studies. By designing eight substation LDNs deployed on slope-type (ST), mountain-type (MT) and basin-type (BT) terrains, respectively, we employed Monte Carlo simulations to analyze their spatial location accuracy distribution based on time-of-arrival technology. Significant differences among the LDNs on inclined terrains and between them and the LDN on plain-type (PT) terrain were revealed. Compared to the PT LDN, LDNs on inclined terrains exhibited a reduction in high-precision location regions and a shift in the distribution pattern of location accuracy. The ST LDN showed marked deviations in the high-precision vertical location toward the lower slope side with increases in the elevation angle and consistently smaller high-precision vertical location areas compared to MT and BT LDNs. The variations in elevation angles of MT and BT LDNs had a substantial impact on the spatial distribution patterns of both horizontal and vertical location accuracy, with BT LDNs featuring larger vertical high-precision areas than MT LDNs. Our conclusions were further corroborated through an analysis of an actual LDN, which combined characteristics from both ST and MT terrain patterns.

The study of shadowing effect for LTE and 5G networks in suburban environment

Abstract The presence of obstacles in the propagation path is a critical factor in air-to-ground (AG) communication. The behavior of wireless signal propagation depends on several variables, such as frequency, building height, elevation angle, and street design. This paper aims to compare the three established line of sight (LOS) probability model based on actual site data, including the building geometry in suburban environment. The comparison between these three models using the site data provide a guideline for selecting the LOS probability model based on the optimistic and pessimistic predictions. The shadowing loss was evaluated at frequencies 2 and 3.5 GHz with an elevation angle of 20° in two suburban locations at Universiti Tun Hussein Onn Malaysia. Three prediction models, ITU-R P.1410-5, Holis and Pechac, and Pang et al., available in the literature were used to identify and compare the line-of-sight probability. By focusing on the shadowing model in suburban area, the guideline for optimizing LOS communications or navigation in these challenging environments can be developed. The finding highlights the importance of considering building height in AG communication for network performance evaluation and design.

Kinematic Movement Differences Between Petanque Pointing and Shooting Technique in Children

This study aimed to evaluate children's kinematic movement in petanque pointing and shooting techniques. There were 16 male beginner petanque athletes (aged 11.37 ± 1.36 years old, weight 42.37 ± 4.36 Kg, and height 151.37 ± 7.36 cm) who were selected using the purposive sampling method. The successful throwing was observed in the sagittal plane and measured by kinematic analysis in Kinovea 0.9.4 Software. There were pointing and shooting kinematic data, categorized into four phases, i.e., back swing, zero position, release, and follow throw position. As a result, there were significantly different in several variables of each phase between pointing and shooting techniques. There was a significant difference in the back swing phase at shoulder extension and ball height (α < .05). The shooting technique showed greater velocity (10.94 ± 13.34 m/s) than pointing (5.290 ± 0.44 m/s). In the release phase, every variable was significantly different (α < .05). The ball height in pointing was higher (92.53 ± 9.69 m) than in shooting (80.19 ± 10.74 m). Ball velocity at pointing was slower (6.46 ± 0.43 m/s) than shooting (16.09 ± 5.18 m/s). The release elevation angle at pointing was wider (42.38 ± 5.85 o) than shooting (35.31 ± 7.26 o). There were significant differences in trunk flexion, knee flexion, maximum ball height, and ball velocity at the follow-throw phase (α < .05). Ball velocity at pointing was slower (4.90 ± 2.35 m/s) than shooting (13.01 ± 5.36 m/s). In conclusion, the specific technique in shooting and pointing could be adapted in the training method for children to advance the result and successful possibility. Further study could be conducted in different age groups and gender to gain more information about the petanque throwing technique. Key Words: biomechanics, gait analysis, manipulative skill, training evaluation

Modelling the elevation power angle spectrum of a MIMO channel

<p>Multiple-Input Multiple-Output (MIMO) channel modelling is constantly researched, and the innovation of its three-dimensional (3D) models is the introduction of the elevation domain parameters, in particular the elevation angle of arrival (EOA) and elevation angle of departure (EOD) where their power angle spectrum (PAS) and their angular spread (AS) greatly impact the 3D MIMO performance. PAS is the basic characteristic used to estimate and model angular dispersion in wireless channels. Propagating signal waves are constrained into a path having an angle within which the power is contained. One of the scenes that will have a significant effect on these parameters is the relative height between the BS and the building. They will also depend on the distance between the base station (BS) and the user equipment (UE). In this work, we investigate the effect of distance and height on the power angle spectrum of a street canyon and a high-rise scenario in the urban environment. The wireless Insite X3D ray tracing engine and a 3D digital map of the environment were used for the simulation. It is seen that the elevation power spectrum (EPS) in the elevation domain decreases with distance and height in both scenarios for the arrival and departure. The appearance of multiple peaks leads to a double-normal distribution in the arrival of the high-rise as height increases, which is a result of reflections from multiple clusters. The azimuth power spectrum (APS) in the azimuth domain also decreases with distance and height at the arrival but increases with distance and height at the departure. The result of the power angle spectrum in this work can be used for modelling angular dispersion as well as designing adaptive antennas for wireless communication.</p>

Multi-user communications for line-of-sight large intelligent surface systems

In this paper, we propose a new interference-suppression beamformer design and a Direction-of-Arrival (DoA) estimation method for Line-of-Sight (LoS) multi-user communication systems with circular Large Intelligent Surfaces (LISs). This symmetrical circular-shaped LIS allows signals defined on it to be formed by combining Fourier and Bessel series. The Fourier harmonics are orthogonal along the rotational direction and the Bessel functions constituting the Bessel series are orthogonal along the radial direction. Synthesizing basis functions from these two series results in the proposed interference-suppression beamformer, with their coefficients designed to cancel inter-user interference. Also by exploiting signal structure of a circular LIS communicating with Mobile Stations (MSs), we devise a DoA estimation method to obtain directional information of incoming signals. Under LoS channel, the DoA corresponds to elevation and Azimuth angles of MSs relative to the LIS. This method is numerically demonstrated to have promising performance with high-frequency carriers.

Different contributions of PROG1 and TAC1 to the angular kinematics of the main culm and tillers of wild rice (Oryza rufipogon).

PROG1is necessary but insufficient for the main culm inclination while TAC1partially takes part in it, and both genes promote tiller inclination in Asian wild rice. Asian wild rice (Oryza rufipogon), the ancestor of cultivated rice (O. sativa), has a prostrate architecture, with tillers branching from near the ground. The main culm of each plant grows upward and then tilts during the vegetative stage. Genes controlling tiller angle have been reported; however, their genetic contributions to the culm movement have not been quantified. Here, we quantified their genetic contributions to angular kinematics in the main culm and tillers. For the main culm inclination, one major QTL surrounding the PROG1 region was found. In cultivated rice, tillers firstly inclined and lately rose, while it kept inclining in wild rice. It was suggested that PROG1 affected the tiller elevation angle in the later kinematics, whereas TAC1 was weakly associated with the tiller angle in the whole vegetative stage. Micro-computed tomography (micro-CT) suggested that these angular changes are produced by the bending of culm bases. Because near-isogenic lines (NILs) of wild rice-type Prog1 and Tac1 alleles in the genetic background of cultivated rice did not show the prostrate architecture, the involvement of another gene(s) for inclination of the main culm was suggested. Our findings will not only contribute to the understanding of the morphological transition during domestication but also be used in plant breeding to precisely reproduce the ideal plant architecture by combining the effects of multiple genes.

Analysis of Illumination Conditions in the Lunar South Polar Region Using Multi-Temporal High-Resolution Orbital Images

The illumination conditions of the lunar south pole region are complex due to the rugged terrain and very low solar elevation angles, posing significant challenges to the safety of lunar landing and rover explorations. High-spatial and temporal-resolution analyses of the illumination conditions in the south pole region are essential to support mission planning and surface operations. This paper proposes a method for illumination condition analysis in the lunar pole region using multi-temporal high-resolution orbital images with a pre-selected landing area of Chang’E-7 as the study area. Firstly, a database of historical multi-temporal high-resolution (0.69–1.97 m/pixel) orbital images, with associated image acquisition time, solar elevation angle, and azimuth angle, is established after preprocessing and registration. Secondly, images with the nearest solar elevation and azimuth at the planned time for mission operations are retrieved from the database for subsequent illumination condition analysis and exploration support. The differences in the actual solar positions at the mission moments from that of the nearest sun position image are calculated and their impact on illumination conditions is evaluated. Experimental results of the study area demonstrate that the constructed image database and the proposed illumination analysis method using multi-temporal images, with the assistance of DEM in a small number of cases, can effectively support the mission planning and operations for the Chang’E-7 mission in the near future.

A novel efficient estimator for three‐dimensional bearings‐only source localisation with unknown sensor altitude and systematic measurement errors

AbstractA novel two‐stage profile maximum likelihood estimator is proposed to estimate the source location and the systematic errors jointly, with the aim of addressing the problem of source localisation using angle‐only measurements from a single sensor with unknown sensor altitude and systematic measurement errors. The proposed two‐stage profile maximum likelihood estimator algorithm is capable of decoupling the azimuth and elevation angle measurements while transforming the original maximum likelihood optimisation problem into two sub‐problems, that is, two‐dimensional‐projected maximum likelihood estimator and relative altitude maximum likelihood estimator. In terms of the two‐dimensional‐projected maximum likelihood estimator, an algorithm combining pseudo‐linear estimating and Kalman filtering is proposed to generate an initial estimate. Subsequently, a Gauss–Newton iterative method is developed to estimate the two‐dimensional‐projected target location and the azimuth systematic error jointly. The relative height maximum likelihood estimator is initialised using a pseudo‐linear estimator. Next, a Gauss–Newton iterative algorithm is adopted to estimate the elevation systematic error and the relative height. As indicated by the result of the simulation studies, the proposed algorithm exhibits an estimation performance close to the Cramér–Rao lower bound with unknown sensor altitude and systematic measurement errors.

Heliostat Wind Load Field Measurements at the University of Adelaide Atmospheric Boundary Layer Research Facility (ABLRF)

The University of Adelaide has recently commissioned a facility dedicated to investigating the atmospheric boundary layer (ABL) for the analysis of wind loads on full-scale heliostats. Wind tunnel testing is an affordable way to analyse loads on a scaled structure before committing to a full-scale design. Scale testing however has its challenges as most cases in literature fail to correctly scale the ABL when scaling a model due to the differences between the ratio of the heliostat chord to the boundary layer depth in a wind tunnel and ABL. There is a lack of direct comparison between wind tunnel and full-scale heliostat wind loads. The Atmospheric Boundary Layer Research Facility (ABLRF) consists of arrays of ultrasonic anemometers and a 1.5 aspect ratio heliostat, mounted on a 6-axis load cell, for the comparison of loads measured in the wind tunnel with a full-scale model. Preliminary results categorise the site to have a roughness of 0.01 m to 0.03 m indicating open country farmland, when compared to standards. Comparison between coefficients of lift force, drag force, and hinge moment on the heliostat model at a single elevation angle at the ABLRF and wind tunnel models in literature verify the commissioning of the site, allowing for further in-depth analysis of wind load coefficients at varying elevation and azimuth angles.

Theoretical algorithm for maximum jump height of the conductor after ice-shedding considering elevation angle and nonlinearity

The determination of maximum jump height of the conductor in ice zones is extremely important for the design of transmission line. Considering the elevation angle and nonlinearity, the theoretical formulas for maximum jump height of the conductor after ice-shedding is derived. Based on the catenary equation theory, simplified models of a single span horizontal and inclined conductors following ice-shedding are built using the same and different two suspension points respectively. Regarding ice-shedding of the conductor as a sudden loading, the energy conversion equation about the maximum jump height is established based on the energy method. Combined with the cable structure theory, the formulas for maximum jump height of the horizontal and inclined conductor are presented. Additionally, finite element method (FEM) was carried out with software Ansys on a single span horizontal and inclined conductor under different span length, initial stress and mass ratio ice-conductor.The accuracy of the presented formulas was verified by the results of maximum jump height for simulated conductors. Finally, error analysis is conducted considering the nonlinear change of dynamic tension. And some formulas are revised according to the reasons of errors.The calculated results of revised formulas match the FEM analysis results better, thus the accuracy of these formulas is improved. The given formulas establish the quantitative relationship between the maximum jump height and the sag of the conductor, maximum sag difference in midspan, the dimensionless frequency and the mass ration ice-conductor. The presented formulars for maximum jump height meet the engineering design requirement and provides theoretical guidance for conductor lines design.

Rancang Bangun Antena Rotasi Dengan Kalibrasi Berbasis Program Kalman Filter

The Internet of Things (IoT) has changed how we interact with our environment. Low-Power Wide-Area Networks (LPWAN) such as LoRa play an important role in the IoT ecosystem due to their low power consumption, long-distance communication, and cost-effectiveness. However, detecting the azimuth and elevation angles of the transmitter is a challenge in LoRa communication. This paper proposes a rotary antenna system with an Inertial Measurement Unit (IMU) to precisely track azimuth and elevation angles at LoRa. The research carried out is to test the tool by comparing the algorithm without the Kalman Filter and the one with the Kalman Filter, where the test's success with the lowest error is up to 0.75% and 0%, respectively.

Satellite-based assessment of national carbon monoxide concentrations for air quality reporting in Finland

Carbon monoxide (CO) has negative health effects, especially on the respiratory system, when present in large concentrations in ambient air. Therefore, it is one of the 12 air pollutants with monitoring and assessment obligations set by the European Union Ambient Air Quality Directives. With low CO concentrations in Finland, continuous surface measurements are not compulsory but the monitoring and assessment obligation remains. Currently, there are no air quality stations equipped with CO measurements in Finland, and the assessment can only be based on emission estimates.In this work, we demonstrate the use of satellite-based CO measurements from the TROPOspheric Monitoring Instrument (TROPOMI) on-board Sentinel-5 Precursor satellite (S5P) to strengthen the assessment with actual measurements. Averaging satellite measurements over several years reveals the spatial distribution of CO with nationwide coverage in city-scale resolution. Individual satellite measurements, in turn, are used to estimate the surface concentrations and their annual variability in different regions in Finland.For the surface estimates, we used a simple and robust linear model between the satellite measurements and ground-level in-situ measurements. We found that the linear model produces reasonable surface concentration estimates to be used in air quality assessments where the objective is to evaluate whether the monitoring threshold set by the EU is exceeded on a yearly scale. It is noted that cloudiness can cause local data gaps of several days and the low solar elevation angles prevent satellite measurements from 9 to 18 weeks during the winter time in Finland.In Finland, the average total columns show low spatial variability, with only a few high-concentration areas identified. For the last three years, the estimated surface concentrations have stayed well below the lower assessment threshold set by the Air Quality Directive.

A novel visual representation method for multi-dimensional sound scene analysis in source localization problem

A visual representation method, DoAgram, for multi-dimensional sound scene analysis is suggested. The visual representation of the sound source localization result gives intuitive information about the estimated one to the end user. Also, image-based deep learning is popularly used in the acoustic field nowadays, so such a visualized one can be used for data augmentation. To analyze the spatial sound scene for the moving source, the method displays the estimated azimuth angle and elevation angle of the source, and its corresponding time stamp and frequencies as RGB color channels and metadata by mapping the spatial coordinate to color space. Even though the suggested method is human-interpretable, decoding is needed for the quantitative analysis. Therefore, the time and frequency scanning method, and a histogram to estimate the DoA of the source are proposed. An experiment is conducted in an anechoic chamber to localize two quadcopter drones that have a mean angular velocity of 8°/s ± 9°/s (95 % CI) and 25°/s ± 31°/s (95 % CI), respectively, and the spatial sound scene analysis is implemented using the proposed methods. The test result shows that the trajectories with respect to the time of each source are well separated. Also, an additional test is conducted using an open-access audio dataset for machine learning. The cumulative source mapping method is adopted for the spatial sound scene analysis, and the decoded result shows that the DoAgram is feasible to adopt for machine learning applications.

Performance of single axis tracker technology and automatic battery monitoring in solar hybrid systems

Utilization of elevation angles and azimuth angles is a very important part in maximizing solar energy into electrical energy in photovoltaic (PV). One way to maximize PV power output is to design a single axis tracker system and take into account the azimuth and elevation angles of the sun using the sun position calculator application. The single axis tracker system is set based on the position of the angle of inclination of the surface of the PV 45°, then the angle of 90° and the angle of inclination of 135°. The test results show that the single axis tracker PV system design can work based on the angle settings that have been programmed. Then the use of a battery control system to support the PV reliability system automatically cuts off electricity when the battery voltage drops below 12 V during cloudy weather conditions and excessive battery usage. The integration of the PZEM-017 module with the battery will support monitoring of battery power usage in real time. PV energy data conversion performance uses single axis tracker technology for maximum power reaching 631.72 Watt DC at 12.00 pm and the lowest power reaching 56.02 Watt DC at 6.00 pm.

Modeling and Design for a Sun Tracker Prototype Using Solar Cell and Arduino

Solar cells are devices that can convert sunlight into electrical energy directly using photovoltaic technology. One of the factors that influences optimal absorption from solar cells is the installation of the solar cell surface. Installing the solar cell surface perpendicular to direct sunlight will maximize the energy produced. But in reality, most solar cell installations are still static or permanent with a fixed elevation angle so the solar cells cannot get the maximum intensity of sunlight because the sun always moves from east to west. Based on the existing problems, this prompted the author to create a prototype sun tracker to optimize solar cell absorption. This research uses experimental research methods with methods of data collection, observation, literature study, and system development from planning, needs analysis, design, testing, and results analysis. This system will work by directing the surface of the solar cell so that it is perpendicular to the direction of sunlight to Get maximum solar energy by using Arduino Uno as the main control which gets input values from the LDR sensor which is then processed and Arduino Uno will order the servo motor to move the solar cell towards the incoming sunlight. Monitoring this prototype work system uses a 16x2 LCD and also adds an IoT (Internet of Things) feature for monitoring the prototype work system remotely via smartphone.

Direction-of-arrival estimation of impulse noise using MUSIC algorithm

Spatial information about the source of sounds can be obtained by measuring amplitude and phase differences among multiple microphones in a microphone array. Various methods have been proposed for estimating the direction of arrival, including beam-forming methods, but generally their spatial spectral resolution degrades with a low-frequency source in the far-field. In architectural acoustics, it is important to obtain high spatial resolution in the low-frequency band, especially in investigations to understand phenomena such as sudden impulse noise. In this paper, direction-of-arrival estimation using the MUltiple SIgnal Classification (MUSIC) method is discussed. We propose a microphone array structure designed according to the Cramer-Rao lower limit. It is shown that this technique improves the accuracy of elevation angle estimates at low frequencies while maintaining good horizontal angle estimation accuracy. The proposed method was tested in a real building in which impulse noise occurred and its effectiveness in identifying the source direction with high spatial resolution even at low frequencies was confirmed.