Airborne Ground Research Articles

Three-dimensional numerical simulation and experimental validation of airborne ground-penetrating radar based on CNCS-FDTD method under undulating terrain conditions

Traditional Finite Difference Time Domain (FDTD) approaches face challenges with increased computational demands and errors as terrain complexity and flight altitude rising. This study introduces the Crank-Nicolson-Cycle-Sweep-FDTD (CNCS-FDTD) method, enhancing airborne ground penetrating radar (GPR) simulations over undulating terrains. CNCS-FDTD, as an unconditionally stable implicit algorithm, overcomes these by allowing larger time steps without the constraints of the Courant-Friedrichs-Lewy (CFL) condition. Our research aims to assess how CNCS-FDTD can improve computational efficiency and accuracy in modeling airborne GPR responses across varied terrains. Initial simulations using a three-dimensional graben model indicate that CNCS-FDTD can maintain calculation stability with significantly larger time steps, reducing computational time by 42%. To further verify the reliability of the numerical simulation results, the paper also presents experimental tests of the undulating terrain model. By comparing the numerical and physical simulation results of models under different flight altitudes and terrain conditions, the accuracy of the simulation results is validated.

Assessing the Risk of Uncontrolled Space Debris Re-entry: A Case for Airspace Management and Flight Safety

We explore the risks associated with uncontrolled space debris re-entry and the implications for airspace management and flight safety. With the increasing number of satellites and other objects being launched into space the potential for uncontrolled re-entry events poses a unique challenge for airspace management and public safety. While there have been no recorded instances of aircraft damage or human injury due to re-entering space debris, the increasing frequency of such events necessitates a comprehensive understanding of the associated risks and appropriate mitigation strategies. We briefly examine the current methods for tracking and predicting space debris re-entry, concentrating on the decision-making process for airspace closures, and the risk assessment for ground airborne safety. Our analysis aims to contribute to the ongoing dialogue on space debris management and to inform future policy and operational decisions in the context of civil aviation and public safety.

Domain-knowledge-aided airborne ground moving targets tracking

This paper investigates the problem of traffic surveillance using an unmanned aerial vehicle (UAV) and proposes a domain-knowledge-aided airborne ground moving target tracking algorithm. To improve the accuracy of multiple target tracking, the proposed algorithm incorporates domain knowledge into the joint probabilistic data association (JPDA) filter as state constraints. The domain knowledge considered in this paper includes both road information extracted from a given map and local traffic regulations. Conventional track update method is modified to enhance the capability of recognition of temporarily track loss. A variable structure multiple model (VS-MM) method is developed to assign the road segment to a given target. The main contribution of this paper is that we establish a comprehensive framework for target tracking with the aid of domain knowledge and analyze the effect of diverse constraints on target tracking performance, while the limitations involve only 2-D target behaviors are considered, and the sophisticated interactions between targets are neglected. The effectiveness of proposed algorithm is demonstrated through extensive numerical simulations.

Study on the Three-component Response Characteristics of Ground-airborne Electromagnetic Field

At any point in space, an electromagnetic field consists of three components: Hx, Hy, and Hz. The ground airborne electromagnetic method (GAEM) does not usually retrieve the Hx and Hy components of the electromagnetic field, less data may result in less accurate goaf interpretations. In this study, we numerically simulate the characteristics of the frequency-domain ground-airborne electromagnetic signal sources, quantify the induction signal distribution laws in the x-, y-, and z- directions, and identify the various factors that influence ground-airborne electromagnetic signals. The results of this study provide theoretical support for the future development of a three-component receiver for ground airborne electromagnetic field surveys. Furthermore, this data also provides information that will prove valuable in the design of field work construction.

Modeling and Implementation of a Joint Airborne Ground Penetrating Radar and Magnetometer System for Landmine Detection

We modeled and implemented a joint airborne system integrating ground penetrating radar (GPR) and magnetometer (MAG) models specifically for landmine detection applications. We conducted both simulations and experimental analyses of the joint airborne GPR and MAG models, with a focus on detecting the metallic components of different types of landmines, including antitank (AT) M15 metallic, antipersonnel (AP) M16 metallic, and AT M19 plastic (minimum-metal) landmines. The GPR model employed the finite-difference time-domain (FDTD) method and was evaluated using a singular value decomposition (SVD) and Kirchhoff migration (KM) with matched filtering (MF). These advanced techniques enabled the automatic identification and precise focusing of the reflected hyperbolic signals emitted by the landmines while considering cross-range resolution. Additionally, the MAGs were utilized based on the magnetic dipole model with a de-trend and a spatial median filtering method to estimate the magnetic anomaly of the landmines while considering various data spatial intervals. The joint airborne GPR and MAG system was implemented by combining and integrating the GPR and MAG models for experimental validation. Through this comprehensive approach, which included experiments, simulations, and data processing, the design parameters of the final system were obtained. These design parameters can be used in the development and application of landmine detection systems based on airborne GPR and MAG technology.

Road-Map Aided Gaussian Mixture Labeled Multi-Bernoulli Filter for Ground Multi- Target Tracking

Ground multi-target tracking (MTT) is one of the core tasks of airborne ground moving target indicator (GMTI) radar and automotive radar. However, ground MTT still remains a challenging issue especially in complex traffic scenarios, since it often suffers from high clutter, dense targets, low visibility, etc. To enhance the tracking performance for ground multiple targets, in this paper, we present a comprehensive solution named road-map aided Gaussian mixture labeled multi-Bernoulli filter (RA-GMLMB) filter, which incorporates road-map information into the labeled multi-Bernoulli (LMB) filter. Specifically, we first propose a hybrid circular arc and line segments approximation approach to extract road-map information, which alleviates approximation errors in the procedure of road-map approximation. Then, we deduce the RA-GMLMB filter by integrating the extracted road-map information into the LMB filter with Gaussian mixture implementation. Simulation experiments are conducted and experimental results show that the proposed RA-GMLMB filter outperforms the state-of-the-art methods.

Application of Helicopter-Borne and Ground–Airborne Electromagnetic Detection to Tunnel Engineering Investigation

The Cedaya-S340 Holgutu Highway Construction Project is located in the Mongolian Autonomous Prefecture of Bayingolin in the Xinjiang Uygur Autonomous Region. It is an important traffic channel that connects Luntai County and Hejing County at the southern foot of Tianshan Mountains. As the major component of the highway project, the Huola Mountain Tunnel has a sharp topographic relief, and, therefore, commonly used land geophysical detection instruments cannot work on it. Therefore, we conducted a qualitative survey on the ground-to-air and airborne electromagnetic detection methods used at the Huola Mountain Tunnel site to provide basic data for the design of highway tunnels. The geophysical survey summarized the ground–airborne frequency-domain electromagnetic method (GAFEM) and the helicopter-borne time-domain electromagnetic method (HTEM) developed by Jilin University, and measured 15 measuring lines. Apparent resistivity imaging was performed for each section, and the results were consistent. This study comprehensively analyzed the apparent resistivity profile and geological mapping data. Then, the study inferred the major stratigraphic boundaries, fault fracture zones, rock fragmentation, weakness, karst development, and water content in accordance with background value, low-resistivity anomaly shape, low-resistivity anomaly value, and gradient value in the apparent resistivity profile. Finally, the study identified the scope of two main low-resistivity anomalies, located at the tunnel entrance and exit, respectively, which are basically consistent with the known fault location. The results of this study show that on the basis of the apparent resistivity maps of GAFEM and HTEM, the overall distribution law is basically consistent with site landform, hydrogeology, tectonic geology, and aerial image data. The results provide guidance for the construction of the Huola Mountain Tunnel and ensure the construction safety and progress of the tunnel.

Airborne Validation of ICESat-2 ATLAS Data over Crevassed Surfaces and Other Complex Glacial Environments: Results from Experiments of Laser Altimeter and Kinematic GPS Data Collection from a Helicopter over a Surging Arctic Glacier (Negribreen, Svalbard)

The topic of this paper is the airborne evaluation of ICESat-2 Advanced Topographic Laser Altimeter System (ATLAS) measurement capabilities and surface-height-determination over crevassed glacial terrain, with a focus on the geodetical accuracy of geophysical data collected from a helicopter. To obtain surface heights over crevassed and otherwise complex ice surface, ICESat-2 data are analyzed using the density-dimension algorithm for ice surfaces (DDA-ice), which yields surface heights at the nominal 0.7 m along-track spacing of ATLAS data. As the result of an ongoing surge, Negribreen, Svalbard, provided an ideal situation for the validation objectives in 2018 and 2019, because many different crevasse types and morphologically complex ice surfaces existed in close proximity. Airborne geophysical data, including laser altimeter data (profilometer data at 905 nm frequency), differential Global Positioning System (GPS), Inertial Measurement Unit (IMU) data, on-board-time-lapse imagery and photographs, were collected during two campaigns in summers of 2018 and 2019. Airborne experiment setup, geodetical correction and data processing steps are described here. To date, there is relatively little knowledge of the geodetical accuracy that can be obtained from kinematic data collection from a helicopter. Our study finds that (1) Kinematic GPS data collection with correction in post-processing yields higher accuracies than Real-Time-Kinematic (RTK) data collection. (2) Processing of only the rover data using the Natural Resources Canada Spatial Reference System Precise Point Positioning (CSRS-PPP) software is sufficiently accurate for the sub-satellite validation purpose. (3) Distances between ICESat-2 ground tracks and airborne ground tracks were generally better than 25 m, while distance between predicted and actual ICESat-2 ground track was on the order of 9 m, which allows direct comparison of ice-surface heights and spatial statistical characteristics of crevasses from the satellite and airborne measurements. (4) The Lasertech Universal Laser System (ULS), operated at up to 300 m above ground level, yields full return frequency (400 Hz) and 0.06–0.08 m on-ice along-track spacing of height measurements. (5) Cross-over differences of airborne laser altimeter data are −0.172 ± 2.564 m along straight paths, which implies a precision of approximately 2.6 m for ICESat-2 validation experiments in crevassed terrain. (6) In summary, the comparatively light-weight experiment setup of a suite of small survey equipment mounted on a Eurocopter (Helicopter AS-350) and kinematic GPS data analyzed in post-processing using CSRS-PPP leads to high accuracy repeats of the ICESat-2 tracks. The technical results (1)–(6) indicate that direct comparison of ice-surface heights and crevasse depths from the ICESat-2 and airborne laser altimeter data is warranted. Numerical evaluation of height comparisons utilizes spatial surface roughness measures. The final result of the validation is that ICESat-2 ATLAS data, analyzed with the DDA-ice, facilitate surface-height determination over crevassed terrain, in good agreement with airborne data, including spatial characteristics, such as surface roughness, crevasse spacing and depth, which are key informants on the deformation and dynamics of a glacier during surge.

Intelligent Early Warning Method Based on Drone Inspection

Commonly used UAV emergency inspection methods are executed by the instructions of the ground command center. The response rate depends on the stability of the communication network and the rapid response ability of the commander. The critical time window is fleeting, which is likely to cause unnecessary loss. Crisis rapid response capability has become the key to measuring system capabilities. In order to improve the system’s rapid response capability, a method of deploying decision-making agents on airborne computers and ground early warning systems is proposed. This early warning method uses key technologies such as multi-network integration, situation assessment, neural network architecture, deep learning, reinforcement learning, and intelligent cognitive reasoning to effectively ensure the effectiveness of crisis warning. The early warning method of the early warning system is as follows: the mission computer uniformly collects the flight control status parameters, the load status parameters and the load real-time data form a composite information flow. The task computer adopts the methods of protocol conversion, data classification, and danger recognition to the compound information flow to identify the crisis information and make a preliminary analysis and judgment of the crisis state. If it is determined that it is necessary to track the target in real time, the initial task assignment and parameter adjustment of the load are carried out, and the continuous tracking of the task target is carried out to realize the rapid response to the crisis on the edge side. At the same time, the composite data are downloaded to the command center. The command center performs the secondary crisis analysis and risk level determination and outputs the crisis plan deduced by the agent to realize the strategy assistance. The accuser refers to the plan strategy and issues instructions to the task computer, and the task computer receives it. Instruction and secondary adjustment and optimization of the load parameters. If there is a flight route adjustment instruction, the adjustment route will be sent to the flight controller, which greatly improves the flexibility and efficiency of handling the crisis in the UAV inspection process. By adopting this set of early warning methods, it can provide users with an updated, faster and more efficient way to realize the early warning requirements in drone inspections, which is a new breakthrough in the field of drone command methods.

Grounded electrical source ground–airborne transient electromagnetic modelling with fictitious wave field methods

The finite-difference time domain (FDTD) method is widely used in ground–airborne transient electromagnetic modelling. Generally, this method offers great limitations because the calculation of the air layer is avoided and the surface assumption is flat. This study proposes a new method for ground–airborne 3D electromagnetic forward modelling that includes air layers and effectively solves the airborne TEM forward calculation of the coastal ocean and rugged terrains. The optimum selection of the air-layer resistivity and the identification ability of the long-wire source are discussed. By adding the pulse source signal to the control equation and realizing a direct calculation that includes the source, the cumbersome process of calculating the complex initial field is avoided. After establishing the mountain model and coastal ocean model, the electromagnetic response is discussed. Subsequently, the ground–airborne TEM modelling is subjected to a 3D numerical simulation of complex geological conditions. The validity of this method is verified by analytical solutions through a uniform half space. The results show that the method can achieve 3D and high-precision numerical calculations when it includes complex terrain and seawater.

Determination of wear resistance and wear mechanisms of HVAF coat-ings based on Ni-Al composition depending on the technological modes of their deposition

Presented studies are related to the spheres of aviation and machine-building. World aviation technology experience has accumulated a huge amount of statistical material on the failure airborne systems and ground equipment due to the increased level of parts wear. That is why the issue of research and improvement of anti-wear properties aeronautical parts is one the components when considering the priority directions of ensuring the reliability of operation motor vehicles and friction units. The Ni3Al coating has been deposited on the medium carbon steel using high velocity air fuel deposition. It has been established that it is very sensible for modes of coating deposition and different chemical phenomenon have been detected. The structure of the obtained coating has been thoroughly researched on the electronic microscope. The obtained coating has been tested on the friction bench modeling the fretting process that is taking place in the couple of locking devices of self-propelled passengers stairs. The coating has also corrosion protection. The friction surfaces have been investigated on the electronic microscope and the wear mechanisms have been established. The optimal modes of the HVAF coting deposition from the viewpoint of wear resistance have been detected

Uncertainty Assessment of Ice Discharge Using GPR-Derived Ice Thickness from Gourdon Glacier, Antarctic Peninsula

Ice cliffs within a glacier represent a challenge for the continuity equations used in many glacier models by interrupting the validity of input parameters. In the case of Gourdon Glacier on James Ross Island, Antarctica, a ∼300–500 m high, almost vertical cliff, separates the outlet glacier from its main accumulation area on the plateau of the island. In 2017 and 2018 we conducted ice thickness measurements during two airborne ground penetrating radar campaigns in order to evaluate differences to older measurements from the 1990s. The observed differences are mostly smaller than the estimated error bars. In comparison to the in situ data, the published “consensus ice thickness estimate” strongly overestimates the ice thickness at the outlet. We analyse three different interpolation and ice thickness reconstruction methods. One approach additionally includes the mass input from the plateau. Differences between the interpolation methods have a minor impact on the ice discharge estimation if the used flux gates are in areas with a good coverage of in situ measurements. A much stronger influence was observed by uncertainties in the glacier velocities derived from remote sensing, especially in the direction of the velocity vector in proximity to the ice cliff. We conclude that the amount of in situ measurements should be increased for specific glacier types in order to detect biases in modeled ice thickness and ice discharge estimations.

Divergence of tipper vector imaging for ground–airborne frequency-domain electromagnetic method with orthogonal sources

The ground–airborne frequency–domain electromagnetic (GAFDEM) method is a recently developed rapid detection approach for underground structures. However, the conventional apparent resistivity imaging in this method cannot meet the requirements of high precision and high efficiency detection for 3D targets. Therefore, we introduce the divergence of tipper vector (DTV) imaging to solve this problem with two orthogonal sources. First, we define DTV for the GAFDEM method, and then, we analyze the characteristics, advantages, and detection principles of DTV imaging using 3D models. Incorporating DTV imaging into the GAFDEM method allows us to directly distinguish the resistivity properties, position, and direction of an anomalous body more clearly and in less computing time, relative to apparent resistivity imaging. Thus, DTV imaging provides a fast detection method with high detection precision for a 3D anomalous body. This may effectively promote the development and application of the GAFDEM method and systems.

Analysis of Bent Wire Antenna Resonant Frequency for Different Bent Angles

AbstractFor the bedrock survey in the temperate glacier regions, low frequency antenna system of the airborne ground penetrating RADAR plays a very important role. A small size antenna, working at 10 MHz, would make its use easier in various radar applications. Reducing the resonant frequency of the wire dipole antenna structure, without increasing the physical size, can be attained by introducing bents in the existing structure. This paper introduces a new bent wire dipole antenna and presents the effects of bent angle of 80°, 70°, 60°, 50°, 45° and 40°of the wire antenna on the antenna parameters such as resonant frequency, S11, VSWR, gain and radiation pattern. A broadband four element equivalent circuit model of a straight dipole is used with some modifications in the R, L, C equations for the new bent wire dipole antenna by utilizing the bent angle. The frequency response of the equivalent circuit model, calculated resonant frequency values using the equations and the simulated results of the bent wire dipole antenna is compared and analyzed. As the antenna placement area inside the anechoic chamber is limited, the size of the 10MHz antenna has been scaled down by a factor of 0.01. This modifies the resonant frequency of the new structure to 1GHz. The scaled down antenna system are simulated, analyzed and tested in a GTEM cell. For bandwidth improvement of the 10 MHz antenna, a lumped element matching circuit has been designed and simulated.

Design of airborne target tracking accelerator based on KCF

The on-board target tracking of unmanned aerial vehicle (UAV) relies on on-board computer to process the collected ground image information, and then use the target tracking algorithm to achieve the target tracking function, which provides the user with target position, trajectory and other information. UAVs are limited by load and power consumption. Due to the high resolution and frame rate of UAV's image collection system, traditional target tracking platforms cannot meet the requirements. As a result, the real-time nature of the tracking platform urgently needs to be resolved. This study designs and implements the airborne ground target tracking accelerator for UAV. The kernelised correlation filters (KCFs) algorithm with low computational complexity and precision is selected to achieve the airborne ground target tracking function and its performance bottleneck is analysed. In order to improve the real-time performance of the tracking task processing, the ZYNQ platform based on ARM and field programmable gate arrays is chosen to achieve the hardware acceleration of the KCF algorithm. The KCF algorithm is implemented in hardware using the high-level synthesis technology, and a high-speed data transmission link is established. Experiments show that the design can achieve a tracking rate of more than 30 FPS under 960 × 540 resolution, which meets the real-time requirements of UAV target tracking task.

An Ultrawide Band Antipodal Vivaldi Antenna for Airborne GPR Application

An ultrawide band (UWB) antipodal Vivaldi antenna is designed for airborne ground penetrating radar (GPR) system. With exponential tapered slots and slot edges, the presented antenna demonstrates a wide operating band from 300 MHz to more than 2 GHz. The fabricated prototype of this antenna with a compact size of 450 mm $\times \,\, 600$ mm $\times \,\, 1.5$ mm has been measured in anechoic chamber. Both simulation and experimental results show that good radiation patterns with gain 4.4–11.5 dBi in the endfire direction could be achieved in the whole working band, which indicates that the proposed antenna is suitable for airborne GPR application.

Depth-Focused Waveform Based on SHEPWM Method for Ground-Airborne Frequency-Domain Electromagnetic Survey

The ground–airborne frequency-domain electromagnetic (GAFDEM) survey is a mixture of ground and airborne electromagnetic methods with a source on the ground and a magnetic field receiver in the air. The technique probes different depths of the earth by transmitting waveforms at different frequencies. Therefore, multiple closely spaced frequencies are needed when surveying a specific target depth in detail. However, in the existing GAFDEM systems using a square wave or a 2 n pseudorandom wave, the ground source needs to transmit more sets of waveforms with different fundamental frequencies in more flights to improve the vertical resolution for the same observed line, which will seriously reduce the exploration efficiency. In this paper, we design a depth-focused waveform to solve this problem based on a new full-cycle asymmetrical selective harmonic elimination pulse width modulation (SHEPWM) method. In the SHEPWM method, we obtain a desired spectrum by directly controlling the switching angles of a binary sequence with an artificial neural network algorithm. In our study, we first provide the basic theory and method for waveform design. Then, we realize the depth-focused waveform and pseudorandom waveform via simulation. Next, we employ the depth-focused waveform into practice and compare it with the 2 n pseudorandom wave in a GAFDEM field survey. The test shows that the survey result with a depth-focused waveform has a higher vertical resolution and efficiency.

Design of Wind Pendulum Control System Based on Improved Genetic PID Algorithm

Aiming at the attitude disturbance of the airborne ground tracking system and the problem of pointing stability under high-frequency vibration, and effectively utilizing the wind power outside the cabin, a new type of airborne ground tracking simulation platform-wind pendulum control system is designed, designed to TMS320F28335 For the control system of the main control chip, the controller adopts an improved genetic PID algorithm to realize the function of rapid braking and movement according to any desired trajectory. The simulation results show that, compared with the traditional PID algorithm, the improved genetic PID algorithm can better solve the problem of chattering, overshoot and non-fast convergence in a limited time in the system. At the same time, it has strong robustness to external disturbances, and can get the full physical simulation needs of airborne ground tracking systems.

Applied geophysics for cover thickness mapping in the southern Thomson Orogen

Potentially mineralised Paleozoic basement rocks in the southern Thomson Orogen region of southern Queensland and northern New South Wales are covered by varying thicknesses of Mesozoic to Cenozoic sediments. To assess cover thickness and methods for estimating depth to basement, we collected new airborne electromagnetic (AEM), seismic refraction, seismic reflection and audio-frequency magnetotelluric data and combined these with new depth to magnetic basement models from airborne magnetic line data and ground gravity data along selected transects. The results of these investigations over two borehole sites, GSQ Eulo 1 and GSQ Eulo 2, show that cover thickness can be reliably assessed to within the confidence limits of the various techniques, but that caveats exist regarding the application of each of the disciplines. These techniques are part of a rapid-deployment explorers’ toolbox of geophysical techniques that have been tested at two sites in Australia, the Stavely region of western Victoria, and now the southern Thomson Orogen in northern New South Wales and southern Queensland. The results shown here demonstrate that AEM and ground geophysics, and to a lesser extent depth to magnetic source modelling, can produce reliable results when applied to the common exploration problem of determining cover thickness. The results demonstrate that portable seismic systems, designed for geotechnical site investigations, are capable of imaging basement below 300 m of unlithified Eromanga Basin cover as refraction and reflection data. The results of all methods provide much information about the nature of the basement–cover interface and basement at borehole sites in the southern Thomson Orogen, in that the basement is usually weathered, the interface has paleotopography, and it can be recognised by its density, natural gamma, magnetic susceptibility and electrical conductivity contrasts.

Can Airborne Ground Penetrating Radars Explore Groundwater in Hyper-Arid Regions?

Groundwater provides roughly 43% of the water used globally for irrigated agriculture. Understanding, predicting, and managing the environmental processes that define the natural capital of Earth’s changing groundwater is one of the most pressing societal challenges of the 21st century. To understand the influence of the dynamics in the vadose zone on terrestrial ecosystems, and to estimate the future sustainability of groundwater resources, a regional and eventually global assessment of water table depth is required. To enable observations of the hydrologic systems’ dynamics, the feasibility of an airborne ground penetrating radar (GPR) system is considered as a first step to effectively provide both large spatial coverage and short revisit times. Such a capability has the potential to enable large-scale surveys to directly observe the shallow subsurface hydrologic processes. To evaluate the capabilities of such a system, we start with a review of soil and subsurface material properties, with a focus on hyper-arid regions. Using first principles, results from literature reviews, and recent field measurements, we then investigate the effects of attenuation and surface clutter to identify the potential capabilities and challenges of an airborne GPR to investigate the spatio-temporal dynamics of the vadose zone. In this paper, we arrive at a qualified “yes” as an answer the title’s question. With low radar frequencies (on the order of 10 MHz or less), adequate ground clutter rejection, and medium or higher vadose zone soil resistivity, the detection of water table depths of 50 m and beyond are feasible.