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Drone-Mounted Ultrawideband Radar for Retrieval of Snowpack Properties
Abstract
Extracting snowpack parameters from snow cover on sea ice or land is a time-consuming and potentially high-risk task. Moreover, deriving such parameters by manually digging a snow pit evidently yields low area coverage. We, therefore, propose a practical solution to this problem by mounting an ultrawideband radar system onto an UAV to obtain information such as snowpack depth, density, and stratigraphy in order to increase personnel safety and extend coverage area. In this paper, we describe the development of radar system hardware and its mounting onto a UAV, as well as initial tests with this radar as a snow measuring device. Preliminary results from both ground and airborne testing show that the radar system is capable of obtaining snow depth information that corresponds well to in situ validation data with a correlation of 0.87. The radar system also works well while mounted on a UAV platform with little additional signal noise from vibrational and translatory movements.
... For this reason, the ground-penetrating radar (GPR) [2] is gaining increasing attention as a complementary remote sensing instrument onboard UAV platforms, and the scientific community, as well as various industries, is attempting to develop innovative and effective UAV-based GPR systems . The combination of UAV and GPR technology can lead to the creation of innovative imaging systems, which could be exploited in many applicative contexts, such as landmine detection [3,[5][6][7]9,10,15,17], glaciology [8,19,23], search and rescue [8], agriculture [16], environmental monitoring [4,11,18], and cultural heritage [12]. ...
... For this reason, the ground-penetrating radar (GPR) [2] is gaining increasing attention as a complementary remote sensing instrument onboard UAV platforms, and the scientific community, as well as various industries, is attempting to develop innovative and effective UAV-based GPR systems . The combination of UAV and GPR technology can lead to the creation of innovative imaging systems, which could be exploited in many applicative contexts, such as landmine detection [3,[5][6][7]9,10,15,17], glaciology [8,19,23], search and rescue [8], agriculture [16], environmental monitoring [4,11,18], and cultural heritage [12]. ...
... System 5 is an ultra-wide-band snow sounder (UWiBaSS) GPR developed by Norut Northern Research Institute (Norway) in 2018 for snowpack surveying [8]. The radar module is the M-Sequence UWB sensor developed by the German company ILMSENS (https://www.uwb-shop.com/, ...
Radar imaging from unmanned aerial vehicles (UAVs) is a dynamic research topic attracting huge interest due to its practical fallouts. In this context, this article provides a comprehensive review of the current state of the art and challenges related to UAV-based ground-penetrating radar (GPR) imaging systems. First, a description of the available prototypes is provided in terms of radar technology, UAV platforms, and navigation control devices. Afterward, the paper addresses the main issues affecting the performance of UAV-based GPR imaging systems. such as the control of the UAV platform during the flight to collect high-quality data, the necessity to provide accurate platform position information in terms of probing wavelength, and the mitigation of clutter and other electromagnetic disturbances. A description of the major applicative areas for UAV GPR systems is reported with the aim to show their potential. Furthermore, the main signal-processing approaches currently adopted are detailed and two experimental tests are also reported to prove the actual imaging capabilities. Finally, open challenges and future perspectives regarding this promising technology are discussed.
... UAS-borne radars could cover larger areas with respect to terrestrial systems, with a shorter return time. These two characteristics, combined with the flexibility of UAS systems, allow for the use of UAS in different applications, such as landmine detection [12], snow/ice monitoring [13], deformation measurement [14], and biomass survey [15]. Compared to conventional systems, the UAS radar can be deployed within minutes and used in scenarios where ground systems cannot be operated. ...
... For UAS applications, the FMCW is the most used (63% of papers), followed by pulsed equipment (18%), and finally SFCW (2.5%). In [13,26,27], Jessen et al. used a pseudo noise transceiver, which is an advanced modulation technique usually used for military purposes since it is more robust against the interference (it cannot be easily intercepted or jammed). Moreover, the authors selected this modulation due to a flatter amplitude inside the transmitted bandwidth, and a higher duty cycle. ...
... applications, the FMCW is the most used (63% of papers), followed by pulsed equipment (18%), and finally SFCW (2.5%). In [13,26,27], Jessen et al. used a pseudo noise transceiver, which is an advanced modulation technique usually used for military purposes since it is more robust against the interference (it cannot be easily intercepted or jammed). Moreover, the authors selected this modulation due to a flatter amplitude inside the transmitted bandwidth, and a higher duty cycle. ...
Since the 1950s, radar sensors have been widely used for the monitoring of the earth’s surface. The current radars for remote sensing can be divided into two main categories: Space/aerial-borne and ground-based systems. The unmanned aerial system (UAS) could bridge the gap between these two technologies. Indeed, UAS-borne radars can perform long scans (up to 100/200 m) in a brief time (a few minutes). From the 2010s, the interest in UAS-borne radars has increased in the research community, and it has led to the development of some commercial equipment and more than 150 papers. This review aims to present a study on the state-of-the-art of UAS-borne radars and to outline the future potential of this technology. In this work, the scientific literature was categorized in terms of application, purpose of the paper, radar technology, and type of UAS. In addition, a brief review of the main national UAS regulations is presented. The review on the technological state-of-the-art shows that there is currently no standard in terms of radar technology, and that the multi-helicopter could be the most used UAS in the near future. Moreover, the UAS-borne radar can be used for several remote sensing applications: From landmine detection to smart agriculture, and from archeological survey to research and rescue applications. Finally, the UAS-borne radar appears to be a mature technology, which is almost ready for industrialization. The main developmental limit may be found in the flight regulation, which does not allow for many operations and imposes strict limits on the payload weight.
... The UWiBaSS discussed in this paper is a ground-penetrating radar system developed for drone-mounted operations. A preceding iteration of this radar system was presented in [5]. ...
... where B is the effective bandwidth of the radar transmitter and receiver and r is the complex relative dielectric constant. Equation (5) shows that the radar system bandwidth is a fundamental parameter of the range resolution and, theoretically, the only factor that can be modified to improve the range resolution significantly. For high-valued dielectric media, r also has a marked impact on the range resolution. ...
... The radar system consists of an ILMsens SH-3100 radar sensor, a Minicircuits ZX60-83LN12+ amplifier for the TX channel, dual Vivaldi antennas in a bistatic configuration and an Odroid XU2 single board acquisition computer. The system is described in more detail in [5], and the new improved antenna system is described in Section 3.3 below. The integration with the UAV is illustrated in Figure 2 where the block diagram of the UWiBaSS illustrates synchronization and data transfer between the UAV autopilot as well as antenna angle regulation. ...
Drone borne radar systems have seen considerable advances over recent years, and the application of drone-mounted continuous wave (CW) radars for remote sensing of snow properties has great potential. Regardless, major challenges remain in antenna design for which both low weight and small size combined with high gain and bandwidth are important design parameters. Additional limiting factors for CW radars include range ambiguities and antenna isolation. To solve these problems, we have developed an ultra-wideband snow sounder (UWiBaSS), specifically designed for drone-mounted measurements of snow properties. In this paper, we present the next iteration of this prototype radar system, including a novel antenna configuration and useful processing techniques for drone borne radar. Finally, we present results from a field campaign on Svalbard aimed to measure snow depth distribution. This radar system is capable of measuring snow depth with a correlation coefficient of 0.97 compared to in situ depth probing.
... Due to low operating cost and noninvasive field data collection capability, an unmanned aerial vehicle (UAV)mounted ultrawideband (UWB) ground penetrating radar (GPR) received much attention in various applications such as buried mines detection, 1 soil moisture mapping, 2 snow thickness measurement, 3,4 and mapping of civil infrastructure. 5 To analyze the internal layers of the ground (soil, ice, or snow) with fine resolution, the GPR requires an UWB system. ...
... where c is the speed of light and ε r is the complex permittivity of the medium. 3 Further, the GPR demands a system with a low first crossing frequency (f L ) of the voltage standing wave ratio (VSWR) under 2 and high antenna gain because the attenuation of electromagnetic (EM) waves increases with frequency as it penetrates the medium. f L of 500 MHz is needed to penetrate 4 m thick of 5% wet snow ground. ...
This paper presents a novel high‐gain, miniaturized, and ultra‐wideband tapered‐slot Vivaldi antenna (TSVA) for ice‐sounding radar applications. To miniaturize the antenna and improve the impedance matching and antenna gain of conventional TSVA, tapered slot edge, circular cavity, rectangular cavity, inner circular patch, and rectangular slit structures are newly designed and introduced. The simulation results show that the size of the designed Vivaldi antenna is reduced by 15% and increases the peak realized gain by up to 5.1 dBi, compared to the conventional Vivaldi antenna. The optimized Vivaldi antenna was fabricated and characterized for its antenna performance. The simulated results are in good agreement with the measured results.
... In [27], [28], the trajectory and precoder of UAV-BS are optimized to maximize physical layer secrecy. In [29], a UAV-radar is used in measuring the depth of the snow on the sea. Human detection and classification by a UAV-radar have been studied in [30]. ...
... The maximum node densities λ d and λ s.o. r can be obtained when (29) goes to equality. Note that this analysis can be easily extended to the condition that λ d and λ s.o. ...
Unmanned aerial vehicles (UAVs) are expected to be used extensively in the future for various applications, either as user equipment (UEs) connected to a cellular wireless network, or as an infrastructure extension of an existing wireless network to serve other UEs. Next generation wireless networks will consider the use of UAVs for joint communication and radar and/or as dedicated radars for various sensing applications. Increasing number of UAVs will naturally result in larger number of communication and/or radar links that may cause interference to nearby networks, exacerbated further by the higher likelihood of line-of-sight signal propagation from UAVs even to distant receivers. With all these, it is critical to study network coexistence of UAV-mounted base stations (BSs) and radar transceivers. In this paper, using stochastic geometry, we derive closed-form expressions to characterize the performance of coexisting UAV radar and communication networks for spectrum overlay multiple access (SOMA) and time-division multiple access (TDMA). We evaluate successful ranging probability (SRP) and the transmission capacity (TC) and compare the performance of TDMA and SOMA. Our results show that SOMA can outperform TDMA on both SRP and TC when the node density of active UAV-radars is larger than the node density of UAV-comms.
... The drones, compared to the helicopter, can enjoy a much lower flight altitude, down to about 1 m according to our experience. The application of drone-borne GPR to investigate glacier environments is a novelty in the literature and has only been addressed by a few studies, such as Jenssen et al. (2018Jenssen et al. ( , 2020 [19,20]. Those works focus on the development of an ultrawideband radar antenna, operating in a frequency band between 0.95 to 6 GHz, which can be mounted effectively on an octocopter drone. ...
... A better vertical resolving power could be achieved by adopting higher frequency antennas: a customized release of the commercial antennas up to 2 GHz could be easily implemented in our system, allowing us to double the vertical resolution. Recent research tested a specifically built antenna for airborne GPR surveys, designing a specific unambiguous range, range resolution, and frequency bandwidth [20]. Their results on the snow cover test point out that airborne surveys can reach good accuracy and resolution with an adequate design. ...
Ground-penetrating radar (GPR) is one of the most commonly used instruments to map the Snow Water Equivalent (SWE) in mountainous regions. However, some areas may be difficult or dangerous to access; besides, some surveys can be quite time-consuming. We test a new system to fulfill the need to speed up the acquisition process for the analysis of the SWE and to access remote or dangerous areas. A GPR antenna (900 MHz) is mounted on a drone prototype designed to carry heavy instruments, fly safely at high altitudes, and avoid interference of the GPR signal. A survey of two test sites of the Alpine region during winter 2020–2021 is presented, to check the prototype performance for mapping the snow thickness at the catchment scale. We process the data according to a standard flow-chart of radar processing and we pick both the travel times of the air–snow interface and the snow–ground interface to compute the travel time difference and to estimate the snow depth. The calibration of the radar snow depth is performed by comparing the radar travel times with snow depth measurements at preselected stations. The main results show fairly good reliability and performance in terms of data quality, accuracy, and spatial resolution in snow depth monitoring. We tested the device in the condition of low snow density (
... We assume that the radar image is already preprocessed with both matched filtering and frequency-domain noise filtering. These basic preprocessing steps for the UWB radar data are described in more detail in [25,26]. ...
... The ultra-wideband snow sounder (UWiBaSS) is a custom-developed radar system for drone-mounted snow measurements. Papers [25,26,43] detail recent advances of the radar system. New developments include retrofitting the radio frequency (RF) operation band as well as digital modules with 3D printed casings coated in conductive paint to reduce weight while still offering electromagnetic interference (EMI) protection. ...
The use of uav-mounted radar for obtaining snowpack parameters has seen considerable advances over recent years. However, a robust method of snow density estimation still needs further development. The objective of this work is to develop a method to reliably and remotely estimate swe using uav-mounted radar and to perform initial field experiments. In this paper, we present an improved scheme for measuring swe using uwb (0.7GHz–4.5GHz) pseudo-noise radar on a moving uav, which is based on airborne snow depth and density measurements from the same platform. The scheme involves autofocusing procedures with the f-k migration algorithm combined with the Dix equation for layered media in addition to altitude correction of the flying platform. Initial results from field experiments show high repeatability (R>0.92) for depth measurements up to 5.5 m, and good agreement with Monte Carlo simulations for the statistical spread of snow density estimates with standard deviation of 0.108 g/cm3. This paper also outlines needed system improvements to increase the accuracy of a snow density estimator based on an f-k migration technique.
... irborne radar systems operating at microwave and millimeter-wave frequencies are a key technology for wide-area determination of snow cover thickness, ice-sheet firn density, and superficial topography variations in cold regions. By exploiting differences in signal penetration depths and backscattering signatures at different bands, these systems can accommodate diverse measurement scenarios to capture spatial and temporal changes of snow cover properties [1][2][3][4][5][6][7][8]. ...
... These features became realizable as technology advanced in recent years. Currently, the operation of high-performance aerial radar systems for snow studies involves the following main scenarios: (1) separate large-and mid-size systems operating onboard platforms with moderate restrictions on payload size, weight and power (SWaP) [18][19][20][21]; (2) separate single-band compact instruments for operation on manned or unmanned vehicles [2], [22][23][24][25][26][27]; and/or (3) inherently multi-band systems with relatively narrow-band capabilities [28][29]. ...
We developed a portable ultra-wideband radar system capable of reconfigurable operation in multiple frequency bands (separate or simultaneous) spanning from microwaves through millimeter-waves. The instrument provides a compact solution for fine-resolution measurements of elevation changes and superficial snow/firn thickness from low-altitude, mid-sized airborne platforms. In this paper, we provide an overview of the radar system design and its performance during laboratory testing. We demonstrate its application in aerial surveys of snow layer thickness at S/C bands, dual-band airborne altimetry at Ku/Ka-bands, and present first-order comparisons with coincident airborne lidar data.
... I N RECENT years, the use of microwave sensors based on ultrawideband (UWB) technology has received considerable attention for noninvasive remote sensing applications. Some relevant applications are medical imaging, detection and monitoring [1]- [3], ground-penetrating radar (GPR) [4], [5], and positioning [6]. Impulsive UWB systems, which transmit and receive pulses of short duration, are a versatile technology for nondestructive characterization of samples because the scattered field produced by the targets is highly dependent on its composition and shape [7]. ...
... This slab was reserved for validation purposes only, and it was not used during the learning process. Using each vector x i , we computed f (x i ), as in (5). The boxplot shows the median along with the 0.25 and 0.75 quantiles. ...
This paper presents the design of an impulsive ultra-wideband test-bed, developed for remote sensing of dielectric targets. The platform is used for estimating the moisture content in polyamide targets. The main aspects of the design are presented, together with measurements of the constructed prototype. The capability of the platform to estimate the moisture content is explored and validated through measurements of Nylon 6 targets through a non-linear regression algorithm. The experimental results show that the platform is capable of estimating the moisture content with good accuracy even when the target or the environment are not completely known.
... Parallelly, the technological progress has led the development of GPR systems that can be used remotely with an extremely high signal-to-noise ratio. Some examples of this upgraded configuration are mainly related to landmine detection (Garcia-Fernandez et al. 2018a;Garcia-Fernandez et al. 2019a, 2019bGarcia-Fernandez et al. 2022;Šipoš and Gleich 2020), snowpack and glaciology research (McCallum and Fairweather 2013;Tan et al. 2017;Briggs et al. 2018;Eckerstorfer et al. 2018;Jenssen et al. 2020;Prager et al. 2022;Vergnano et al. 2022;Emilsson et al. 2022), agricultural research (Wu et al. 2019;Hou et al. 2021), archaeological survey (Yarleque et al. 2017;Colica et al. 2022), soil characteristics under railways mapping (Bayisa et al. 2015), investigation of water and sediment depths of lakes and rivers (Bandini et al. 2022), and buried objects detection (Ludeno et al. 2017). ...
This paper describes scientific research conducted to highlight the potential of an integrated GPR-UAV system in engineering-geological applications. The analysis focused on the stability of a natural scree slope in the Germanasca Valley, in the western Italian Alps. As a consequence of its steep shape and the related geological hazard, the study used different remote sensed methodologies such as UAV photogrammetry and geophysics survey by a GPR-drone integrated system. Furthermore, conventional in-situ surveys led to the collection of geological and geomorphological data. The use of the UAV-mounted GPR allowed us to investigate the bedrock depth under the detrital slope deposit, using a non-invasive technique able to conduct surveys on inaccessible areas prone to hazardous conditions for operators. The collected evidence and the results of the analysis highlighted the stability of the slope with Factors of Safety, verified in static conditions (i.e., natural static condition and static condition with snow cover), slightly above the stability limit value of 1. On the contrary, the dynamic loading conditions (i.e., seismic action applied) showed a Factor of Safety below the stability limit value. The UAV-mounted GPR represented an essential contribution to the surveys allowing the definition of the interface debris deposit-bedrock, which are useful to design the slope model and to evaluate the scree slope stability in different conditions.
... Improved ultra wideband radars (UWBs) have also been installed in airplanes to find 2 out the snow depth on the Arctic sea ice [9]. In addition, recently unmanned aerial vehicles (UAVs), known as drones, have been used to retrieve snow depth information on sea ice [10]. One solution is to use satellite microwave remote sensing data for the snow depth estimation on lake and sea ice [11,12]. ...
In this work, backscattering signatures of snow-covered lake ice and sea ice from X- and Ku-band synthetic aperture radar (SAR) data are investigated. The SAR data were acquired with the ESA airborne SnowSAR sensor in winter 2012 over Lake Orajärvi in northern Finland and over landfast ice in the Bay of Bothnia of the Baltic Sea. Co-incident with the SnowSAR acquisitions in-situ snow and ice data were measured. In addition, time series of TerraSAR-X images and ice mass balance buoy data were acquired for the Lake Orajärvi in 2011-12. The main objective of our study was to investigate relationships between SAR backscattering signatures and snow depth over lake and sea ice, with the ultimate objective of assessing the feasibility of retrieval of snow characteristics using X- and Ku-band dual-polarisation (VV and VH) SAR over freshwater or sea ice. This study constitutes the first comprehensive survey of snow backscattering signatures at these two combined frequencies over both lake and sea ice. For lake ice, we show that X-band VH-polarized backscattering coefficient (σo) and the Ku-band VV/VH-ratio exhibited the highest sensitivity to the snow depth. For sea ice, the highest sensitivity to the snow depth was found from the Ku-band VV-polarised σo and the Ku-band VV/VH-ratio. However, the observed relations were relatively weak, indicating that at least for the prevailing snow conditions, obtaining reliable estimates of snow depth over lake and sea ice would be challenging using only X- and Ku-band backscattering information.
... Reviews of the state-of-the-art of UAV-based GPR systems have been presented in [14], [15], [16], describing the main features and challenges faced by these systems. Although most of the UAV-based GPR system prototypes developed in the last years have been devoted to detecting landmines and IEDs, they have been also introduced in other application areas like snow moisture and ice thickness measurement [17], [18], soil moisture characterization [19], or search and rescue missions [20], [21], among others. ...
The usage of Unmanned Aerial Vehicles (UAV)-based Ground Penetrating Radar (GPR) systems has gained interest over the last years thanks to advantages over ground-based systems such as contactless inspection and capability to reach difficult-to-access areas. The former is of paramount importance concerning the detection of buried threats such as Improvised Explosive Devices (IEDs) and landmines. Current state-of-the-art UAV-based GPR systems are able to provide centimeter-level resolution thanks to the use of GPR-Synthetic Aperture Radar (SAR) processing techniques. One of the challenges to keep improving these systems is the scanning throughput, that is, the area that can be scanned in a given time. This contribution presents an array-based GPR-SAR system for subsurface imaging, aiming at maximizing the scanning throughput without jeopardizing the imaging capabilities of the system. First, the antenna array is mounted on a portable setup to evaluate its performance and imaging capabilities. Next, the antenna array is integrated into the UAV platform, and the UAV-based GPR-SAR system with the array is tested in realistic scenarios with different kinds of buried targets. Results show that the scanning throughput is significantly improved and, furthermore, the coherent combination of all transmitting-receiving channels of the array provides enhanced detection capabilities.
... Also, the sUAS radar must be operated at as high altitudes as possible in conformance with Federal Aviation Administration (FAA) regulations to collect data over areas covered with heavy vegetation over complex terrain. Tan et al. [14] and Jessen et al. [15]- [17] designed and tested UWB UASbased radars using a vector network analyzer or a Pseudo noise signal generator for snow depth measurements. However, the short unambiguous range of these systems limits their benefits to open areas. ...
This paper presents results from a field deployment of a small Unmanned Aircraft System (sUAS) radar in Colorado-Grand Mesa during Spring-2022 for measurements over snow. The stand-alone, low-power, compact, and Frequency Modulated Continuous Wave (FMCW) radar on a sUAS is used for these measurements. The radar operates over the frequency range of 2.8-5.8 GHz. The transmit signal is obtained by down-converting 77-81 GHz chirp generated with an automotive radar. The radar operates with a low output power of only 3 dBm (2 mW) to mitigate interference to nearby communication systems with a chirp duration of 250 μs. The received signal is up-converted back to 77-81 GHz for digitization and processing using the automotive radar data capture board. The radar data are processed with a fully focused Synthetic Aperture Radar (SAR) algorithm after applying phase and amplitude corrections to the transmitter chirp to obtain nearly ideal point target responses. The radar mapped air-snow and snow-ground surface interfaces as well as the snow internal layers with snow depth exceeding 2 m in areas covered with 15-25 m tall trees. In addition, the radar-generated snow thicknesses are within ±10 cm of in-situ measurements.
... However, even though the satellite platforms can cover large areas, the resolution is coarse for measurements over complex terrains. On the other hand, Tan et al. and Jessan et al. demonstrated the snow measurements using low-cost drone platforms with fine resolution [24][25][26]. Airborne platforms like DHC-6 Twin Otter give a unique advantage in bridging this gap and can cover broad areas with very fine resolution. A combination of manned aircraft with drones can provide both fine-resolution data over small areas and modest resolution data over large areas. ...
We developed and deployed a high sensitivity and low transmit power airborne UWB FMCW radar for snow depth measurements. The radar has a near-ideal point target response so that we can produce near-real-time snow thickness maps after each survey flight. The improved performance is achieved by carefully designing the radar hardware to reduce internal reflections between various components, third-order products generated by mixers, higher-order harmonics generated in multipliers and non-linear devices, and amplitude and phase errors in transmitted chirp signals. In addition, we performed extensive linear and non-linear system simulations to predict degradations in the radar hardware in advance and applied the remedies to correct them. These improvements allowed for near-real-time data products to be generated by reducing the need for advanced signal processing techniques. We also developed a T-shape Mills-Cross antenna array to obtain a small overlapped footprint of transmit and receive antennas. We performed measurements over snow in Grand Mesa, Colorado, from March to April 2022, and the radar mapped the top and bottom interfaces and density changes of 1.2-2.1m of snow. We generated a snow thickness map from the data collected over the grid flown and compared results with in-situ measurements. The comparison between radar estimates and in-situ measurements shows that the average snow depths obtained from the radar data are within a standard deviation from the mean of in-situ measurements.
... Recently, drones have been used as vehicles to transport on-board sensors for various purposes (Vivow and Udawatta, 2016;Renwick et al., 2016;Shin et al., 2017;Suh et al., 2017;Dering et al., 2019;Jensen et al., 2020). It is interesting to highlight in this context the study carried out by Joseph et al. (2016) who used lightweight electronics and multiple antennas mounted on a drone to perform radio frequency (RF) measurements in the GSM 900 MHz band. ...
Personal exposimeters are currently used in studies assessing human exposure to electromagnetic fields. These devices are usually carried by an individual, but vehicles such as bicycle or car are also used. The aim of the present study was to propose a personal exposimeter attached to a drone to perform environmental radio-frequency measurements. Trials were carried out to determine whether: (i) the wireless communication between the remote controller and the drone affects the downlink mobile telephony bands by a cross-talk effect, and (ii) the structure of the drone alters the measurements of the exposimeter compared to when the meter is on a tripod. To apply this system to a real scenario, a 3D representation of the electric field in a building was obtained, and the attenuation due to the building of radiation from outside was estimated. Measurements of the electromagnetic field with this system will make it possible to monitor without risk the emissions of antennas in their close vicinity, and to validate propagation models experimentally.
... Low-frequency ultrawideband (UWB) millimeter radar has good penetration capacity and offers potential for imaging building interiors. Previous demonstrations of UAV SAR include the P, L, and C bands [212] for civil and deformation monitoring applications; X band [213] for calculating the scattering characteristics of complex targets; P and C bands for estimating the terrain height of a eucalyptus forest [214]; UWB [215] for snow coverage scanning; and W band [216] to minimize the size and weight of the hardware, among others, and different or full polarization combinations, e.g., horizontal and vertical backscatters. ...
... Low-frequency ultrawideband (UWB) millimeter radar has good penetration capacity and offers potential for imaging building interiors. Previous demonstrations of UAV SAR include the P, L, and C bands [212] for civil and deformation monitoring applications; X band [213] for calculating the scattering characteristics of complex targets; P and C bands for estimating the terrain height of a eucalyptus forest [214]; UWB [215] for snow coverage scanning; and W band [216] to minimize the size and weight of the hardware, among others, and different or full polarization combinations, e.g., horizontal and vertical backscatters. ...
Remote sensing-based forest investigation and monitoring have become more affordable and applicable in the past few decades. The current bottleneck limiting practical use of the vast volume of remote sensing data lies in the lack of affordable, reliable, and detailed field references, which are required for necessary calibrations of satellite and aerial data and calibrations of relevant allometric models. Conventional field investigations are mostly limited to a small scale, using a small quantity of observations. Rapid development in close-range remote sensing has been witnessed during the past two decades, i.e., in the constant decrease of the costs, size, and weight of sensors; steady improvements in the availability, mobility, and reliability of platforms; and progress in computational capacity and data science. These advances have paved the way for turning conventional expensive and inefficient manual forest in situ data collections into affordable and efficient autonomous observations.
... The development of technologies suited for long-range Arctic missions, such as finding shorter and safer shipping routes, geological survey for undiscovered rare earth elements, delivering medical supplies to remote areas, aquaculture inspection, Search & Rescue (SAR) operations, surveillance & reconnaissance, and tracking Arctic ice and vegetation for climate change study are important but difficult challenges [7], [8]. Unmanned Aircraft Systems (UAS/drones) is a key enabling technology for such missions in the harsh Arctic environment [9]. ...
The Arctic is one of the least developed and most under-invested regions in the world, primarily due to its harsh environment and remoteness. However, with the current retreat of Arctic sea ice, the pristine Arctic region is gradually open for economic activities and has been of great interest for Arctic council members. For example, the European Union (EU) Integrated Policy for the Arctic has a clear emphasis on the issues specific to the European Arctic. In particular, it focuses on sustainable Arctic maritime economic growth and launches a process of identifying and developing its relevant key enabling technologies. Unmanned Aircraft System (UAS) or drone is a key enabling technology for missions in harsh and remote Arctic environment, such as finding shorter and safer shipping routes, geological survey for undiscovered rare earth elements, delivering medical supplies to remote areas, Search & Rescue operations, and tracking Arctic ice and vegetation for climate change study. In this paper, we present challenges, opportunities, and enabling technologies related to the development of UAS for Arctic applications. Furthermore, we discuss our hands-on experience of flying drones in harsh Arctic environment and provide a list of operational risks and recommendations.
... The development of GPR surveys has been accompanied by separate aerial UAV surveys of the same area in some projects in the Antarctic to provide, for instance, a more complete assessment of ice volumes and surface topography [82,109,111]. Although the integration of GPR sensors in UAV platforms is already technically available, their use in cryosphere studies is still limited to few surveys in the Arctic, namely to measure snowpack properties [213], and still without references in the Antarctic. The benefits of its use are immediate and evident, namely in clear time efficiencies in the development of the field work compared to traditional ground surveys, as well as clear cost advantages when compared to aircraft manned flights. ...
Remote sensing is a very powerful tool that has been used to identify, map and monitor Antarctic features and processes for nearly one century. Satellite remote sensing plays the main role for about the last five decades, as it is the only way to provide multitemporal views at continental scale. But the emergence of small consumer-grade unoccupied aerial vehicles (UAVs) over the past two decades has paved the way for data in unprecedented detail. This has been also verified by an increasing noticeable interest in Antarctica by the incorporation of UAVs in the field activities in diversified research topics. This paper presents a comprehensive review about the use of UAVs in scientific activities in Antarctica. It is based on the analysis of 190 scientific publications published in peer-reviewed journals and proceedings of conferences which are organised into six main application topics: Terrestrial, Ice and Snow, Fauna, Technology, Atmosphere and Others. The analysis encompasses a detailed overview of the activities, identifying advantages and difficulties, also evaluating future possibilities and challenges for expanding the use of UAV in the field activities. The relevance of using UAVs to support numerous and diverse scientific activities in Antarctica becomes very clear after analysing this set of scientific publications, as it is revolutionising the remote acquisition of new data with much higher detail, from inaccessible or difficult to access regions, in faster and cheaper ways. Many of the advances can be seen in the terrestrial areas (detailed 3D mapping; vegetation mapping, discrimination and health assessment; periglacial forms characterisation), ice and snow (more detailed topography, depth and features of ice-sheets, glaciers and sea-ice), fauna (counting penguins, seals and flying birds and detailed morphometrics) and in atmosphere studies (more detailed meteorological measurements and air-surface couplings). This review has also shown that despite the low environmental impact of UAV-based surveys, the increasing number of applications and use, may lead to impacts in the most sensitive Antarctic ecosystems. Hence, we call for an internationally coordinated effort to for planning and sharing UAV data in Antarctica, which would reduce environmental impacts, while extending research outcomes.
... Recently, many research proposed different radar systems to fulfill the foregoing requirements. Tan et al. [4] and Jessen et al. [5] designed an UWB and lightweight UAV radar systems for snow depth measurements using a vector network analyzer (VNA) to generate the signal with a total payload between 3 and 4 kg. Similarly, Wu et al. [6] presented another lightweight ground penetrating radar (GPR) based on a VNA for soil moisture mapping with 200 MHz bandwidth. ...
This letter presents a novel approach to build a compact lightweight unmanned aerial vehicle (UAV) radar for remote sensing applications. The proposed radar exploits the recent advancement of an automotive radar chip for broadband chirp generation and rapid data processing. To compensate for the path losses and improve penetration at the millimeter wave (mm-wave) frequency range, an up- and down-converters are developed to generate an UWB (3.25-5.15 GHz) chirp signal. The total payload of the radar is 2.5 kg. The proposed radar is installed on a UAV and tested in the field at 100 m altitude above the ground surface. The results show that the compact low-power UWB radar can be used to map vegetation and soil moisture with fine resolution.
... Different methods are being implemented to improve the performance of an of ultrawide band (UWB) radar systems, based on the modification of the geometries of the antennas, the use of meta-materials, and the use of lenses (Jenssen et al. 2019;Choudhary et al. 2020). These methods have found applications in ground-based non-destructive testing. ...
we present a printed lens for radar applications. The structure of the presented lens consists of an array of modified micro-strip lines, which is positioned in the antenna’s aperture on the same planar substrate. Simulations show that the gain and directivity increase with the proposed lens in a wide band frequency band. The proposed design is insensitive to rotation of the antenna. This paper focuses on real industrial applications and problems. Further, we show that the lens can be used to improve the object detection ability of an ultrawide band radar system, which is used in industrial applications such as non-destructive monitoring of built-structures and for use in the renovation process. The signal to noise ratio is improved. Furthermore, we show how the microwave lens can also be used to reduce the clutter in applications where the complex refractive index of objects is determined. Further, different simulated results (for different cases) are compared, presented and concluded.
... Machguth et al. (2006) show an early application of helicopter borne GPR for snow thickness profiling on alpine glaciers. Wu et al. (2019) use a frequency domain radar for soil moisture mapping and Jenssen et al. (2019) and Jenssen and Jacobsen (2020) also use a drone-mounted radar for snow thickness estimation. Najad (2020) use a GPR mounted on a drone to map ice and determine freezing rates on Canadian lakes. ...
... Following the encouraging preliminary results, the use of UAV-borne radars has become more attractive in the international scientific community. Recently, an ultrawideband snow sounder was presented in [82]. The system was designed with a focus on low payload weight to fulfill mini-UAV mounting and high-range resolution requirements for snow measurements. ...
This article provides a comprehensive overview of the current state of the art in contactless ground-penetrating radar (GPR) systems. These devices offer many large-scale subsurface sensing possibilities based on different observation platforms and measurement configurations. On the other hand, new challenges must be faced because the radar system is not coupled directly to the ground; hence, data processing plays a crucial role to achieve reliable imaging results. In this respect, microwave tomography (MWT) turns out to be a very flexible tool to address the aforementioned challenges. This methodology allows modeling, in a relatively simple way, of the radar signal propagation in an inhomogeneous medium as well as the handling of arbitrary measurement modalities and radar configurations. Experimental examples regarding different types of contactless GPR are presented to validate the effectiveness of MWT when combined with ad hoc signal filtering procedures.
... The broad measurement capability of the UAV has led to its widespread use in a range of systems including both military and civilian applications [3]- [5]. Unfortunately, to guarantee their metrological traceability and to evaluate their metrological performance (i.e., in terms of measurement uncertainty) involves very difficult tasks. ...
Although Unmanned Aerial Vehicles (UAVs) are used as mobile measurement platforms in several applications, no guidelines are provided to include the measurement uncertainty assessment in the design steps of the UAV platform. In this article, the steps required for the design of a UAV-based measurement instrument according to the application measurement target and the uncertainty assessment are delineated. In order to highlight the necessity of the proposed design guidelines, the case study of 3D reconstruction of archaeological sites is discussed.
... It has also been deployed to aid in the detection of buried landmines, where its use can lead to a significant reduction in the rate of false alarms [2]. Other applications include the evaluation of pavements [3], measuring snow depth [4] and imaging ice sheets [5]. Microwave UWB measurements are also widely used in instruments and measurement devices, for varying applications. ...
Microwave ultra-wideband technology has been widely adopted in instrumentation and measurement systems, including ground-penetrating radar (GPR) sensors. Baluns are essential components in these systems to feed balanced antennas from unbalanced feed cables. Baluns are typically introduced to avoid issues with return signals, asymmetrical radiation patterns and radiation from cables. In GPR systems, these issues can cause poor sensitivity due to a reduction in radiated power, blind spots due to changes in the radiation pattern and additional clutter from common mode radiation. The different balun technologies currently available exhibit a wide variation in performance characteristics such as insertion loss, reflection coefficient and phase balance, as well as physical properties such as size and manufacturability. In this study, the performance of two magnetic transformer baluns, two tapered microstrip baluns and an active balun based on high-speed amplifiers were investigated, all up to frequencies of 6 GHz. A radio frequency current probe was used to measure the common mode currents on the feed cables that occur with poor performing baluns. It was found that commercially available magnetic transformer baluns have the best phase linearity, while also having the highest insertion losses. The active balun design has the best reflection coefficient at low frequencies, while, at high frequencies, its performance is similar to the other baluns tested. It was found that the active balun had the lowest common mode current on the feed cables.
... Moses proposed an X-band radar mounted on a drone in [15] for collision avoidance in a realistic scenario. The use of radars mounted on drones for glaciology [16] and soil moisture mapping [17] has also shown to be effective. ...
In recent years, the demand for small-scale remote sensing, which is used in disaster monitoring, agriculture, and ground subsidence has increased. A multichannel synthetic aperture radar (SAR) system can provide image and topographic information of the illuminated scene, regardless of adverse weather conditions. As a cost-effective solution to radar imaging, a multichannel W-band SAR system mounted on a multirotor unmanned aerial vehicle (UAV) is presented. The radar module was designed to operate at W-band to achieve small size and weight allowing the module to be mounted on multirotor UAVs with small payload. A detailed description of the design and measurement of the system is provided in this paper. The radar imaging capability of the developed system was verified by performing outdoor experiments using isolated buildings as targets. The multichannel functionality of the system was verified by measuring height of a point target placed above the ground. The measurements and experiments verified the feasibility of a multichannel radar mounted on a multirotor UAV for imaging and topographic applications.
... In the past decades, wireless systems and handy devices such as mobile phones and tablets were able to provide different services and tools which require high bandwidth and channel capabilities [1,2]. Moreover, the recent evolution of digital transformation and industry 4.0 lead to a dramatic evolution and diffusion of wireless sensors. ...
... On an appropriate scale, the applications of UAVs cover across multiple disciplines related to cold environments, such as albedo measurement [9], sea-ice characterization [10], navigation over polar ocean [11], snowpack property estimation [12], penguin counting [13], and vegetation ecology [14]. A UAV platform could also mount sounding radar to probe fine-resolution basal topography in the West Antarctic ice sheet [15]. ...
Ice doline is a particular kind of ice morphology, usually scattered on ice-streams which are far from research bases. For this reason, glaciologists rarely have opportunities to document its developments in detail. Satellite observations are too coarse to capture such fine features, whereas Unmanned Aerial Vehicle (UAV)-based Structure-from-Motion (SfM) and Light Detection and Ranging (LiDAR) technologies have revolutionized geosciences research, especially in less accessed polar regions. We developed two bespoke UAV systems for glaciological investigation and carried out four campaigns during two consecutive Chinese Antarctic expeditions in 2017 and 2018. Founded on manual co-registration and accuracy assessment, a successful application to characterize a doline's spatio-temporal evolution is presented in this paper. The overlying weight of surface melting directly triggered the collapse event on 30 Jan 2017 near the Dalk Glacier, then the newborn doline grew for another 8135.6 m2 in area and 280303.38 m3 in volume by early 2018. The UAV-based results revealed the doline's changes during a year, showing a maximum horizontal extension of 50 m and vertical subsidence of more than 10 m. Furthermore, we evaluate the photogrammetry and LiDAR systems and find the former is cost-effective and time-efficient on a large-scale survey while the latter enjoys a better capability to characterize morphological details. Based on systematic comparisons, other pros and cons of the two techniques are discussed. To achieve the best performance for applications in similar scenarios, we recommend adopting an integrated approach, in which LiDAR restores the fine features on the basis of extensive SfM coverage.
... In the context of I&M, monitoring of conditions in extreme environments with a variety of instruments becomes increasingly possible. This is seen in applications like underwater acoustic monitoring and remote sensing [26][27][28]. ...
The field of Instrumentation and Measurement (I&M) is constantly and rapidly changing. These changes manifest themselves as evolutions of technologies and techniques but also as innovations. They come from the technical creativity of people in this field and also from advances in other fields. Conversely, advances in I&M also lead to advances in other fields. Given this two-way relationship, while it is impossible to know the future, we can look at emerging trends across different technological fields and application realms and begin to predict what trends may be at the forefront of I&M over the next five years. These trends can be examined as Trends of Choice and Trends of Consequence (Fig. 1).
Recent research has highlighted the potential for high-resolution, high-density, 3D and 4D ground-penetrating radar (GPR) acquisitions on alpine glaciers. When carried out on foot, such surveys are laborious and time consuming, which limits their application to small domains of limited glaciological interest. Further, crevasses and other hazards make the data acquisition risky. To address these issues, we have developed a drone-based GPR system. The system has a payload weight of 2.2 kg and a data output rate of 14 traces per second. An 80-MHz antenna and a recording time of 2800 ns mean that depths of over 100 m can be reached in temperate ice. Differential GPS positioning assures accurate flight paths. At a speed of 4 m s ⁻¹ and height of 5 m above the glacier surface, our system can acquire over 4 line-km of GPR data in 20 min on a single set of drone batteries. After presenting the technical specifications of the system and tests required to optimize its performance, we showcase a recently acquired 3D dataset from the Otemma glacier in Switzerland, where 462 parallel GPR profiles were surveyed at a 1-m line spacing, totaling over 112 line-km of data, in only 4 days.
A talajnedvesség-tartalom variabilitásának mérését jelentősen megnehezíti a talaj heterogenitása és a környezeti változatosság. Jelenleg még nem fejlesztettek ki olyan univerzális módszert, amely a magas vagy alacsony talajnedvesség-zónák szántóföldi léptékű feltérképezésére alkalmas úgy, hogy a talajnak és a talajnedvesség áramlásának teljes zavarásmentességét nagy mélységben is biztosítja.
A talajnedvesség-mérés részben (talajkapcsolt), vagy teljesen roncsolásmentes (levegőkapcsolt) lehetőségét biztosítja a földradar (GPR), amely nagy felbontást és jelentős behatolási mélységet biztosít a közepes léptékű talajnedvesség meghatározáshoz, így hiánypótló technikát jelent a kisléptékű pontszerű és a nagyléptékű távérzékelt mérési technikák közötti metodikai hiány kitöltésére. Emellett jobb időhatékonyággal alkalmazható más roncsolásos és roncsolásmentes eljárásokkal összevetve.
A talajradart sikeresen alkalmazták a talajnedvesség-meghatározásra, de hidrológiai vizsgálatokban történő alkalmazásának nagy potenciálja ellenére nem minden körülmény között működik optimálisan. Felhasználhatósága többnyire olyan területekre korlátozódik, ahol viszonylag alacsony az elektromos vezetőképesség (az elektromágneses hullám gyenge csillapodására való tekintettel). Ezen túlmenően egyes talajradar módszerek működésének alapfeltétele a jól azonosítható és folyamatos jelvisszaverődés, továbbá a dielektromos állandó tekintetében a földradar-rendszerek térben folyamatos felszín alatti kontrasztot igényelnek.
A talajnedvesség és annak áramlása kulcsparaméter a mezőgazdaság különböző területein. A talajnedvesség (és a talajvíz) látja el a növényeket, ami elengedhetetlen feltétele a növények fejlődésének. Ennélfogva a talaj nedvességtartalmának, eloszlásának, áramlásának, valamint a beszivárgás sajátosságainak alapos és lokális ismerete az öntözés hatékony megvalósításának alapköve, különösen a félszáraz és száraz éghajlatú területeken.
A talajradar mérési alapjaival, valamint hasznosítási lehetőségeivel összefüggésben az elsősorban nemzetközi szakirodalmat összegezve megállapítható, hogy a GPR előnyös mérőeszköz lehet, amely segíthet a talaj nedvességeloszlásának feltérképezésében, tekintettel a beszivárgásra, a párolgás és a növényi vízfelvétel okozta vízveszteségre is. Következésképpen mezőgazdasági felhasználhatósága lehetséges.
A talajradar hasznos része lehet a „Smart farming”-nak (intelligens gazdálkodás), segítséget nyújthat a talajban elhelyezett talajnedvesség-mérő szenzorok kijelölésében. Különösen, ha a közelmúltban megjelent új, szimultán többeltolásos és többcsatornás (SiMoc) GPR rendszerre asszociálunk, amely gyors talajprofil-feltérképezést tesz lehetővé a hét vevőegységével, de a hagyományos egycsatornás GPR sebességével.
Ha a teljes roncsolásmentesség a cél, úgy a drónra szerelt levegőkapcsolt GPR-ek nyújthatnak lehetőséget. Megjegyzendő azonban, hogy a talaj-levegő határfelületen jelentkező szignifikáns jelcsillapodás (hullámszóródás) következtében a feltárási mélység jelentősen csökken.
A földradar végső soron mérési alapul szolgálhat a hatékony (precíziós) öntözési gazdálkodás kialakításához, és a megfelelő vízfelhasználási hatékonyságot biztosítva járulhat hozzá a precíziós mezőgazdasági programok megvalósításához.
Current methods of snowpack stability assessment primarily rely on professional observations, mainly digging a snow pit. This technique has spatial limitations, is time-consuming, and places observers at risk. The combined usage of UAVs and GPR is capable of providing detailed snowpack layering data at scale without human exposure to potential avalanche-prone areas. The presented study aims to obtain radargrams of the study area's internal snowpack layering structure. A single-channel GPR with a 1000 MHz shielded antenna is attached to a UAV to survey the snowpack. The UAV flights are carried out semi-automatically from a safe spot at a speed of 1 m/s at a LiDAR altimeter-adjusted distance to the snow surface of 5 m. The data obtained by the GPR is then compared to density measurements and manual snowpack observations following international standards. The preliminary results indicate the success of the UAV's flight performance and the accuracy of the GPR data in determining the snow depth and detecting the most prominent layers of the snowpack.
Unmanned aerial vehicles (UAVs) are expected to be used extensively in the future for various applications, either as user equipment (UEs) connected to a cellular wireless network, or as an infrastructure extension of an existing wireless network to serve other UEs. Next generation wireless networks will consider the use of UAVs for joint communication and radar and/or as dedicated radars for various sensing applications. Increasing number of UAVs will naturally result in larger number of communication and/or radar links that may cause interference to nearby networks, exacerbated further by the higher likelihood of line-of-sight signal propagation from UAVs even to distant receivers. With all these, it is critical to study network coexistence of UAV-mounted base stations (BSs) and radar transceivers. In this paper, using stochastic geometry, we derive closed-form expressions to characterize the performance of coexisting UAV radar and communication networks for spectrum overlay multiple access (SOMA) and time-division multiple access (TDMA). We evaluate successful ranging probability (SRP) and the transmission capacity (TC) and compare the performance of TDMA and SOMA. Our results show that SOMA can outperform TDMA on both SRP and TC when the node density of active UAV-radars is larger than the node density of UAV-comms.
This study aims to investigate the layer structure within an alpine snowpack using UAV-borne GPR. Weak layers are the target of this survey as they are relevant with regards to the formation of slab avalanches, being the most frequent type of avalanche when it comes to avalanche fatalities and infrastructural damage. The main goal is to evaluate this innovative approach through several field campaigns where both airborne GPR data and manual snow pit observations including stability tests are acquired. The data are then compared to assess the feasibility of this method to detect weak layers within the snowpack, and its suitability to contribute to quality enhancement in avalanche forecasting and monitoring is critically evaluated. Application is also assumed to be successful for infrastructural avalanche monitoring purposes, e.g., along roads and railways, or to assess slope stability in case of freeride contests to minimize risk for professional riders. In a future, more mature state of the research project, it is aimed to automatically analyze the remotely acquired GPR data.
Due to the increasing number of aerial radars and joint communication/sensing technologies, interference from uncoordinated radars will limit the target detection and ranging performance in the future. In this paper, we investigate the interference behavior in an aerial radar network for sensing ground targets. We consider that the radars mounted on unmanned aerial vehicles (UAVs) that fly at a certain altitude are randomly distributed according to a two-dimensional homogeneous Poisson point process (HPPP), and that the propagation is modeled using a probabilistic line-of-sight (LoS) channel model. For such a sensing network, we derive the distribution of the radar interference using a stochastic geometry based analysis. In particular, when Swerling I model is considered for radar cross-section area (RCS) for the target, we derive the Laplace transform of the radar interference. To avoid a strong interference between neighboring radars, a guard zone is introduced within which the UAV radar transmission around the permitted active radar is inhibited. As the radar performance metric, we derive the successful ranging probability (SRP) of a given radar by exploiting the Laplace transform of radar interference. Using the analytic SRP, we show that we can optimize the radar network parameters such as the radius of the guard zone and the density of the active radars. In addition, we also discuss how the analytic SRP gives an insight into the spectrum utilization strategy for the UAV radar networks with the guard zones.
The field of multicopter unmanned aerial vehicles (UAVs) has seen massive technological advances and decreasing costs over the last decade. Due to the higher prevalence and availability of these multicopter UAVs, there have also been rapid improvements in the software interfaceability, enabling the easy integration of custom software for flight planning and controllers. This opened up completely new possibilities, such as low-cost individual aerial photography, the most common civilian application. Furthermore, lightweight multicopters became widely accessible to the public, boosting the development of UAVs even more.
Nowadays, the ultrawideband (UWB) has become a popular solution to the indoor localization problem of quadrotor unmanned aerial vehicle (UAV) due to its low power consumption and ease of implementation. Nonetheless, the accuracy of UAV localization is affected by the skew-
$t$
measurement noises of the UWB sensor induced mainly by the nonline-of-sight (NLOS) errors and the multipath effects, and the uncertainties in the UAV dynamics caused by external wind disturbances. In this article, a composite filtering approach is proposed for time difference of arrival (TDOA)-based UWB localization of the quadrotor UAV. The main advantage of the composite filtering approach lies in its capability of dealing with the skew-
$t$
measurement noises and the dynamic uncertainties simultaneously. Specifically, the external winds are estimated and rejected in real time via the disturbance observer (DO). Meanwhile, the posterior state distribution under skew-
$t$
measurement noises is updated in an iterative fashion within the variational Bayes (VB) framework. The effectiveness of the proposed approach is validated through both numerical simulation and experimental tests on a quadrotor UAV.
MonitoringMonitoring efforts for remote high-latitude and high-altitude glacierized regions heavily rely on remote sensingRemote sensing. Rapid ongoing changes in polarPolar and cryosphericCryosphere environments owing to contemporary climate changeClimate change have attracted more attention towards these regions than ever before. Satellite Satellitesremote sensingRemote sensing has its own limitations related to low sun angles in high latitudes, high acquisition costs for high-resolution images, and persistent cloud cover over ice-dominated land and oceanOceans surfaces. As such, over the past several years, small unoccupied aerial systems (sUAS)Small unoccupied aerial systems (sUAS) have become a viable data collection tool to address the challenges related to spaceborne or expensive airborne remote sensingRemote sensing for monitoringMonitoring the cryosphereCryosphere and polarPolar regions. This chapter discusses sUASSmall unoccupied aerial systems (sUAS) adaptations for collecting data on snowSnow, glaciers, permafrostPermafrost, polarPolar biology, the oceanOceans, and atmosphereAtmosphere; the challenges of conducting sUASSmall unoccupied aerial systems (sUAS) operations in polarPolar latitudes; and the advantages and disadvantages of the technology. It also provides resources that can be used to guide future efforts in applying sUASSmall unoccupied aerial systems (sUAS) to polar and Polarcryospheric researchCryosphere.
Advances in unmanned aerial vehicle (UAV) technology have fostered its use in a wide range of areas, such as agriculture and forestry, surveillance and security, and infrastructure inspection. One of the advantages of UAVs is their ability to conduct remote inspection and sensing by placing different kinds of sensors on board them. In this sense, UAV-based ground-penetrating radar (GPR) systems are of particular interest as they bring together the advantages of UAVs and GPR, resulting in contactless subsurface sensing and imaging systems capable of performing a fast scanning of difficult-to-access scenarios. This contribution reviews the advances on UAV-based GPR systems, describing their architecture and subsystems. In particular, an analysis of different UAV-based GPR systems is presented, focusing on the technical solutions adopted in each case and the detection capabilities that have been achieved. Attention will be also given to the methodologies implemented to obtain 3D high-resolution images of the underground. Finally, the main challenges faced by these systems concerning further improvements of the scanning throughput and the detection accuracy will be discussed.
We present results from a field campaign to measure seasonal snow depth at Cameron Pass, Colorado, using a synthetic ultrawideband software-defined radar (SDRadar) implemented in commercially available Universal Software Radio Peripheral (USRP) software-defined radio hardware and flown on a small hexacopter unmanned aerial vehicle (UAV). We coherently synthesize an ultrawideband signal from stepped frequency 50-MHz subpulses across 600–2100-MHz frequency bands using a novel nonuniform nonlinear synthetic wideband waveform reconstruction technique that minimizes sweep time and completely eliminates problematic grating lobes and other processing artifacts traditionally seen in stepped waveform synthesis. We image seasonal snow across two transects: a 400-m open Meadow Transect and a 380-m forested transect. We present a surface detection algorithm that fuses data from LiDAR, global navigation satellite system (GNSS)/global positioning system (GPS), and features in the radargram itself to obtain high precision estimates of both snow and ground surface reflections, and thus total snow depth, represented as two-way travel time. The measurements are validated against independent ground-based ground-penetrating radar measurements with correlations coefficients as high as
$\rho = 0.9$
demonstrated. Finally, we compare backscattered radar data collected by the UAV-SDRadar while hovering proximal to a known snow pit with
in situ
measured snow dielectric profiles and demonstrate imaging of snow stratigraphy.
In near-field measurements, the correction of the field probe influence is crucial for achieving high accuracy. With the increasing interest in antenna measurements based on unmanned aerial vehicles (UAVs), probe correction becomes essential also in this field. Here, the actual probe comprises the UAV together with the mounted probe antenna and in particular also the rotors which are spinning during flight. In this contribution, we investigate the field modulation caused by the rotating rotor blades of an unmanned aerial vehicle. We show that the arising modulation depends on the polarization of the used probe antenna as well as on the spatial separation from the UAV. It is also revealed that the rotor-caused modulation effect correlates with the rotation speed and that it is independent of the actual measurement frequency.
Adaptive and targeted allocation of mobile sensing agents, in the form of unmanned aerial vehicles (UAVs) with software defined radar (UAV-SDRadar) payloads, enable mapping of surface soil moisture in regions where
in situ
wireless sensor networks (WSNs) undersample soil moisture or upscaling models perform poorly. This work presents an optimization-based UAV path planning methodology that seeks to maximize UAV flight coverage over areas where a complementing WSN yields upscaled soil moisture estimates with high uncertainty. By recursively mapping soil moisture over such areas, the combined UAV and WSN instrumentation can gradually capture the domain’s true mean soil moisture. A series of numerical simulations are presented to demonstrate the algorithm’s basic function while considering real-world and feasible operational scenarios.
This study demonstrates the potential value of a combined UAV Photogrammetry and ground penetrating radar (GPR) approach to map snow water equivalent (SWE) over large scales. SWE estimation requires two different physical parameters (snow depth and density), which are currently difficult to measure with the spatial and temporal resolution desired for basin‐wide studies. UAV photogrammetry can provide very high‐resolution spatially continuous snow depths (SD) at the basin scale, but does not measure snow densities. GPR allows nondestructive quantitative snow investigation if the radar velocity is known. Using photogrammetric snow depths and GPR two‐way travel times (TWT) of reflections at the snow‐ground interface, radar velocities in snowpack can be determined. Snow density (RSN) is then estimated from the radar propagation velocity (which is related to electrical permittivity of snow) via empirical formulas. A Phantom‐4 Pro UAV and a MALA GX450 HDR model GPR mounted on a ski mobile were used to determine snow parameters. A snow‐free digital surface model (DSM) was obtained from the photogrammetric survey conducted in September 2017. Then, another survey in synchronization with a GPR survey was conducted in February 2019 whilst the snowpack was approximately at its maximum thickness. Spatially continuous snow depths were calculated by subtracting the snow‐free DSM from the snow‐covered DSM. Radar velocities in the snowpack along GPR survey lines were computed by using UAV‐based snow depths and GPR reflections to obtain snow densities and SWEs. The root mean square error of the obtained SWEs (384 mm average) is 63 mm, indicating good agreement with independent SWE observations and the error lies within acceptable uncertainty limits.
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Airborne synthetic aperture radar (SAR) sensors have been commonly used during the last decades to monitor different phenomena in medium-scale areas of observation, such as object detection and characterization or topographic mapping. The use of unmanned aerial vehicles (UAVs) is a cost-effective solution that offers higher operational flexibility than airborne systems to monitor these types of scenarios. The Universitat Politècnica de Catalunya has developed the first fully polarimetric SAR system at X-band integrated into a small UAV multicopter platform (UAV MP). The sensor, called AiR-based remote sensing, has been integrated into the platform overcoming restrictions of weight, space, robustness, and power consumption. To demonstrate the validity of the developed system, some measurement campaigns have been conducted in the outskirts of Barcelona, Spain.
High-resolution, downward-looking radar imaging is demonstrated using a small consumer drone. The entire system including an ultra-wideband radar, antennas, camera, and a single-board computer fits on a small drone and is controlled through a Wi-Fi connection. The drone-fitted system is able to collect concurrent radar and video data of the same scene. The measurement results of three real-world settings (trees, parked vehicles, and humans) are presented and discussed.
Synthetic aperture radar (SAR) imaging is demonstrated using a small consumer drone. The entire imaging system including an ultra-wideband radar, antennas, and a single-board computer fits on a small drone and is controlled through a Wi-Fi connection. Motion compensation is carried out based on a prominent scatterer algorithm. The focused SAR image of four trihedrals is validated against simulation. Measured SAR images of a human and a car are also presented.
In this paper, a tapered slot antenna capable of ultra-wideband communication was designed. In the proposed antenna, rectangular slits were inserted to enhance the bandwidth and reduce the area of the antenna. The rectangular slit-inserted tapered slot antenna operated at a bandwidth of 8.45 GHz, and the bandwidth improved upon the basic tapered slot antenna by 4.72 GHz. The radiation pattern of the antenna was suitable for location recognition in a certain direction owing to an appropriate 3 dB beam width. The antenna gain was analyzed within the proposed bandwidth, and the highest gain characteristic at 7.55 dBi was exhibited at a 5-GHz band. The simulation and measurement results of the proposed tapered slot antenna were similar.
The complex dielectric constant of snow has been measured at microwave frequencies. New and old snow at different stages of metamorphosis have been studied. The results indicate that the complex dielectric constant is practically independent of the strncture of snow. For dry snow, the dielectric constant is determined by the density. For wet snow, the imaginary part and the increase of the real part due to liqnid water have the same volumetric wetness dependence. The frequency dependence of the complex dielectric constant of wet snow is the same as that of water. A nomograph for determining the density and wetness of wet snow from its dielectric constant is given. A snow sensor for fielmd easurement of the dielectric constant has been developed. It can be used for determining the density and the wetneosfs snow bya singlem easurement.
The stratigraphy of an alpine snowpack is very important for avalanche danger assessment, as well as interpretation of remote sensing measurements for hydrological purposes. Since spatial variability is often widespread, due mainly to wind, micro-climatic and topographic effects, extrapolating point measurements can be difficult. Tools which can quickly characterize snowpack stratigraphy, such as high frequency radar and mechanical probes, will be required for a complete understanding of the effects of spatial variability, however interpretation of these kinds of measurements still remains challenging. We compare measurements from a portable 8–18 GHz Frequency Modulated Continuous Wave (FMCW) radar with SnowMicroPenetrometer (SMP) and standard snowpit measurements. Although significant variability existed at the sub-meter scale, major stratigraphic horizons could be followed along radar profiles and identified in SMP measurements. A very thin hard crust (0.2–0.4 mm) that was continuous caused strong signals that were identifiable in both the SMP and the radar measurements at five different sites along a 10 m traverse. Two other more subtle transitions in the SMP signal were highly correlated with the locations of radar reflections. This work suggests that combining FMCW radar measurements, to characterize snowpack geometry, with SMP measurements, to characterize mechanical properties of layers, may be a useful technique for quantifying the spatial variability of the snowpack.
During the spring of 2009, an ultrawideband microwave radar was deployed
as part of Operation IceBridge to provide the first cross-basin surveys
of snow thickness over Arctic sea ice. In this paper, we analyze data
from three ˜2000 km transects to examine detection issues, the
limitations of the current instrument, and the regional variability of
the retrieved snow depth. Snow depth is the vertical distance between
the air-snow and snow-ice interfaces detected in the radar echograms.
Under ideal conditions, the per echogram uncertainty in snow depth
retrieval is ˜4-5 cm. The finite range resolution of the radar
(˜5 cm) and the relative amplitude of backscatter from the two
interfaces limit the direct retrieval of snow depths much below ˜8
cm. Well-defined interfaces are observed over only relatively smooth
surfaces within the radar footprint of ˜6.5 m. Sampling is thus
restricted to undeformed, level ice. In early April, mean snow depths
are 28.5 ± 16.6 cm and 41.0 ± 22.2 cm over first-year and
multiyear sea ice (MYI), respectively. Regionally, snow thickness is
thinner and quite uniform over the large expanse of seasonal ice in the
Beaufort Sea, and gets progressively thicker toward the MYI cover north
of Ellesmere Island, Greenland, and the Fram Strait. Snow depth over MYI
is comparable to that reported in the climatology by Warren et al.
(1999). Ongoing improvements to the radar system and the utility of
these snow depth measurements are discussed.
An investigation was made to estimate the variance, measurement errors and sampling error in currently accepted practices for manual snow density measurement carried out as part of snow profile observations using the available variety of density cutters. A field experiment in dry snow conditions was conducted using a randomized block design to account for layer spatial variability. Cutter types included a 500 cm3 aluminium tube, 200 and 100 cm3 stainless-steel box types, 200 cm3 stainless-steel wedge types and a 100 cm3 stainless-steel tube. Without accounting for variation due to weighing devices, the range of values for 'accepted practice' determined in this study included variation within individual cutters of 0.8-6.2%, variation between cutters of 3-12%, variation between cutter means and layer means of 2-7%, and under-sampling errors of 0-2%. The results of a statistical analysis suggest that snow density measurements taken using various density cutters are significantly different from each other. Without adjustment for under-sampling, and given that the mean of all measurements is the accepted true value of the layer density, variation exclusively between cutter types provides 'accepted practice' measurements that are within 11% of the true density.
Ultra-wideband (UWB) sensing is an upcoming technique to gather data from complex scenarios such as nature, industrial facilities, public or private environments, for medical applications, non-destructive testing and many more. Currently it is hard to estimate the full spread of future applications. The measurement approach traditionally used is based on stimulation of the test objects by either short sub-nanosecond impulses or sine waves which are stepped/swept over a wide spectral band. This paper deals with an alternative approach, which uses very wideband pseudo-noise binary signals such as M-sequences for example. Such devices have a very high time stability, enable high measurement speed and do not burden the test objects with high voltage peaks. Furthermore, the device concept promotes monolithic circuit integration in a low cost semi-conductor technology. In what follows, the basic device concept and some extensions will be considered as well as some selected applications will be discussed.
The pioneers of radio science made their first trials of wireless information transmission and demonstrated localization of a steel vessel by radio waves more than 100 years ago. Back then, the world of radio frequencies was organized in a very simple way. The researchers could use any frequency band. There was no interference by others and no controlling government bodies. Since then, governmental authorities have established tight regulations that have split up the available frequency band into small partitions for exclusive use. This article discusses the architecture of a baseband, pseudo-noise UWB radar and gives some examples of applications
This paper presents a Ku-band (14-16 GHz) CMOS frequency-modulated continuous-wave (FMCW) radar transceiver developed to measure dry-snow depth for water management purposes and to aid in retrieval of snow water equivalent. An on-chip direct digital frequency synthesizer and digital-to-analog converter digitally generates a chirping waveform which then drives a ring oscillator-based Ku-Band phase-locked loop to provide the final Ku-band FMCW signal. Employing a ring oscillator as opposed to a tuned inductor-based oscillator (LC-VCO) allows the radar to achieve wide chirp bandwidth resulting in a higher axial resolution (7.5 cm), which is needed to accurately quantify the snowpack profile. The demonstrated radar chip is fabricated in a 65-nm CMOS process. The chip consumes 252.4 mW of power under 1.1-V supply, making its payload requirements suitable for observations from a small unmanned aerial vehicle.
Ground Penetrating Radar (GPR) of antenna frequency 1000 MHz was used for snow depth estimation and snow stratigraphic studies in the Pir Panjal and Greater Himalayan range of NW Himalayas. GPR profiles were acquired at a selected site near Solang observatory (Himachal Pradesh (HP), India) for snow depth estimation. It was observed that the estimated snow depth correlates well with ground measurements taken using snow stakes. Based on these snow depth measurements with GPR and manual density measurement at different locations within the sampling area, the snow water equivalent was also estimated. Experiments were also conducted at Patseo (HP) for snow depth estimation and snowpack layer identification. By analysing the profiles we were able to capture the prominent snow layers present within the snowpack at Patseo. Manual stratigraphy was also performed along with the GPR profiles, and it was found that layer positions in the radargram correspond fairly well with the stratigraphic layer positions. Dielectric constant of snow, which is an important parameter for acquisition/interpretation of GPR profiles was also measured using snow fork.
In this paper, a realization of archimedes spiral antenna for a Radar detector is presented, where this Radar detectors are used to detect Radar signal transmission within the frequency range of 2-18 GHz. In this research, an antenna was designed for the above information band. Multiple frequency bands covered by this antenna S band (2-4 GHz), C band (4-8 GHz), X band (8-12 GHz) and Ku band (12-18 GHz). The designed antenna has a shape of a spiral with a diameter of 5 cm. The antenna was implemented on a Roger Duroid 5880 substrate with εr = 2.2, thickness of 0.787 mm, and 1 oz for copper cladding. These spiral antennas have ultra wideband characteristics due to the planar structure and circular polarization with impedance of 188 Ohm. From the simulation results of the designed antenna, we obtained VSWR of 1.1 up to 1,27, a gain ranging from 3 to 6 dBi, with 3dB bandwidth of 61.7 degree. There is a similarity between the measurements and the simulation results. The realized antennas show advantages, e.g., VSWR <;2 and high gain, compared which the existing antennas in the market.
This paper presents a radar sensor package specifically developed for wide-coverage sounding and imaging of polar ice sheets from a variety of aircraft. Our instruments address the need for a reliable remote sensing solution well-suited for extensive surveys at low and high altitudes and capable of making measurements with fine spatial and temporal resolution. The sensor package that we are presenting consists of four primary instruments and ancillary systems with all the associated antennas integrated into the aircraft to maintain aerodynamic performance. The instruments operate simultaneously over different frequency bands within the 160 MHz-18 GHz range. The sensor package has allowed us to sound the most challenging areas of the polar ice sheets, ice sheet margins, and outlet glaciers; to map near-surface internal layers with fine resolution; and to detect the snow-air and snow-ice interfaces of snow cover over sea ice to generate estimates of snow thickness. In this paper, we provide a succinct description of each radar and associated antenna structures and present sample results to document their performance. We also give a brief overview of our field measurement programs and demonstrate the unique capability of the sensor package to perform multifrequency coincidental measurements from a single airborne platform. Finally, we illustrate the relevance of using multispectral radar data as a tool to characterize the entire ice column and to reveal important subglacial features.
Now-a-days there has been growing interest in dual-pol systems, especially in hybrid-pol mode. In comparison to quad-pol system, the dual-pol system has the advantage of halved average transmitted power and double swath coverage. In this paper, we have discussed, in brief, the benefits of using hybrid-pol scheme. We also present comparisons of hybrid-pol and Quad-pol data based on the amount of information content. The airborne multi-polarization GTRI data set is used for demonstration.
In article was researched, the possibility of improving the characteristics of Vivaldi antenna by use of printed lens located in aperture. It is shown that use of lens leads to increase in gain and reduce level of side lobes. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:369–371, 2014
Cited By (since 1996):47, Export Date: 1 December 2013, Source: Scopus
We describe a prototype ultrawideband radar. We show how the system was designed and how the hardware was developed for the radar prototype. Waveform generation, radar parameters, and signal processing for the stepped frequency waveform are discussed. The radar operates from 500 MHz to 3 GHz with a nominal resolution of 6 cm in air. The advantage of the stepped frequency approach over an impulse radar is better matching between the transmitted waveform and the receiver. We use range gating to improve the system dynamic range. The advantages are illustrated with laboratory measurements and field measurements from glacial ice and permafrost in Svalbard, showing penetration depths of 11 m. Antennas which do not require contact with the ground were developed and used in the experiments.
Snow depth was measured with an L-band frequency-modulated continuous wave (FMCW) radar operating from an aerial tramway up to 70 m above the ground. Snow depth, wetness, and slope varied greatly along the 2.4-km transect, with 640 m of relief. Radar measurements taken in the morning, when the snowpack was frozen were compared against concurrent manual depth probes, and good agreement was found between the estimates. The results suggest that deep snowpacks in rugged terrain can be accurately and safely surveyed by helicopter-borne radar.
The fundamental principles of radar backscattering measurements are presented, including measurement statistics, Doppler and pulse discrimination techniques, and associated ambiguity functions. The operation of real and synthetic aperture sidelooking airborne radar systems is described, along with the internal and external calibration techniques employed in scattering measurements. Attention is given to the physical mechanisms responsible for the scattering emission behavior of homogeneous and inhomogeneous media, through a discussion of surface roughness, dielectric properties and inhomogeneity, and penetration depth. Simple semiempirical models are presented. Theoretical models involving greater mathematical sophistication are also given for extended ocean and bare soil surfaces, and the more general case of a vegetation canopy over a rough surface.
An accurate knowledge of snow thickness and its variability over sea ice is crucial in determining the overall polar heat and freshwater budget, which influences the global climate. Recently, algorithms have been developed to extract snow thicknesses from satellite passive microwave data. However, validation of these data over the large footprint of the passive microwave sensor has been a challenge. The only method used thus far has been with meter sticks during ship cruises. To address this problem, we developed an ultrawideband frequency-modulated continuous-wave radar to measure the snow thickness over sea ice. We synthesized a very linear chirp signal by using a phase-locked loop with a digitally generated chirp signal as a reference to obtain a fine-range resolution. The radar operates over the frequency range from 2-8 GHz. We made snow-thickness measurements over the Antarctic sea ice by operating the radar from a sled in September and October 2003. We performed radar measurements over 11 stations with varying snow thicknesses between 4 and 85 cm. We observed an excellent agreement between radar estimates of snow thickness with physical measurements, achieving a correlation coefficient of 0.95 and a vertical resolution of about 3 cm. Comparison of simulated radar waveforms using a simple transmission line model with the measurements confirms our expectations that echoes from snow-covered sea ice are dominated by reflections from air-snow and snow-ice interfaces.
Conical spiral antennas can have an input impedance and gain that are nearly frequency independent over a wide bandwidth. However, these antennas normally have dispersive properties that produce significant distortion when they are used to radiate a pulse. We examine this dispersion in detail and the possibility of compensating for the dispersion so that the antenna can be used for pulse radiation. First, a simple, qualitative model for this antenna is described. This model provides physical insight into the causes for the dispersion. Next, the antenna is examined using an accurate, full electromagnetic analysis done with the finite-difference time-domain method. Results from this analysis support the conclusions reached with the simple model and provide additional insight into the dispersion. Finally, an approach for compensating for the dispersion in the antenna is described, and the interesting features of the pulse radiated from this antenna, after compensation, are discussed.
Development of an unmanned aircraft mounted software defined ground penetrating radar
- J F Fitter
- A B Mccallum
- J X Leon
J. F. Fitter, A. B. Mccallum, and J. X. Leon, "Development of an
unmanned aircraft mounted software defined ground penetrating radar,"
in Proc. 5th Int. Conf. Geotech. Geophys. Site Characterisation, vol. 5,
2016, pp. 957-962.
Snow Stratigraphy Measurements With UWB Radar
- R.-O R Jenssen
R.-O. R. Jenssen. (2016). Snow Stratigraphy Measurements With UWB
Radar. [Online]. Available: http://hdl.handle.net/10037/11117
Potential of microwave remote sensing for assessing critical snow properties
- C Mätzler
C. Mätzler, "Potential of microwave remote sensing for assessing critical
snow properties," in Proc. Workshop Adv. Techn. Assessment Natural
Hazards Mountain Areas, Innsbruck, Austria, 2000, pp. 38-41.
Development of an unmanned aircraft mounted software defined ground penetrating radar
- fitter
Snow, Weather, and Avalanches: Observation Guidelines for Avalanche Programs in the United States
- E Greene
- K Birkeland
- K Elder
- I Mccammon
- M Staples
- D Sharaf
The complex dielectric constant of snow at microwave frequencies
- M E Tiuri
- A H Sihvola
- E Nyfors
- M Hallikaiken