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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.

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... 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. ...
Article
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.
... In recent years, Unmanned Aerial Vehicle (UAV) or drones have garnered significant research interest in many interesting applications, such as disaster management, surveillance, mapping, medical assistance, policing, and consumer goods delivery [1][2][3]. In this context, autonomous navigation of drones is a critical enabling technology that has conventionally relied on fused measurements of lidar [4] and radio satellite navigation [5]. ...
... where Ψ(Θ k ) = 1 L I L ⊗ a(Θ k )a(Θ k ) H ∈ C LN ×LN . 2 The BCD for two blocks also reduces to alternating optimization. 3 We denote by "cycle"an update of both κ and X. The internal steps of updating entries of the code matrix X are called "iterations". ...
Conference Paper
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The limited battery power of Unmanned Aerial Vehicles (UAVs) is a major challenge in equipping them with onboard radar. Low power results in short flight times, short ranges, and modest radar detection performance. These limitations are overcome by deploying an array of multiple drones. However, challenges due to interference from on-ground services, clutter echoes, and platform motion could distort the antenna radiation pattern. In this paper, we consider beampattern design for a two-dimensional array of multiple single-antenna drones operating in a multiple-input multiple-output (MIMO) radar configuration. The resulting optimization problem has a quartic objective function with constant modulus and discrete-phase constraints enforced to account for hardware limitations. We solve this non-convex problem using a variation of the coordinate-descent algorithm and obtain MIMO transmit waveforms that achieve the desired UAV-borne radar beampattern. Our extensive numerical experiments validate our methods.
... 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. ...
Article
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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. ...
Article
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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]. ...
Article
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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. ...
Article
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.
... 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. ...
Article
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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.
... 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]. ...
Article
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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).
... 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]. ...
Article
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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 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. ...
... 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. ...
Article
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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.
... 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. ...
... 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. ...
... 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. ...
... 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. ...
Article
Full-text available
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.
... 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. ...
Article
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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.
... 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]. ...
Conference Paper
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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 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. ...
Article
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.
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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. This article is protected by copyright. All rights reserved.
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We present an ultra-wideband (UWB) frequency-modulated (FM) microwave radar instrument capable of preserving cm-scale vertical resolution from very long range (verified up to 6 km). The system can operate either as a conventional continuous-wave FM radar (2 GHz to 18 GHz) or in time-delayed stretch processing mode (2 GHz to 14 GHz), providing high sensitivity, fine range resolution, and very low range sidelobes. We present an overview of the system and laboratory tests results to validate its performance. As a practical demonstration of its capabilities, we tested the system’s ability to map snow cover thickness on Arctic marine ice. We present sample results from airborne measurements carried out at altitudes between 500 m to 6 km above ground level onboard a long-range fixed-wing platform.
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Owing to usual logistic hardships related to field-based cryospheric research, remote sensing has played a significant role in understanding the frozen components of the Earth system. Conventional spaceborne or airborne remote sensing platforms have their own merits and limitations. Unmanned aerial vehicles (UAVs) have emerged as a viable and inexpensive option for studying the cryospheric components at unprecedented spatiotemporal resolutions. UAVs are adaptable to various cryospheric research needs in terms of providing flexibility with data acquisition windows, revisits, data/sensor types (multispectral, hyperspectral, microwave, thermal/night imaging, Light Detection and Ranging (LiDAR), and photogrammetric stereos), viewing angles, flying altitudes, and overlap dimensions. Thus, UAVs have the potential to act as a bridging remote sensing platform between spatially discrete in situ observations and spatially continuous but coarser and costlier spaceborne or conventional airborne remote sensing. In recent years, a number of studies using UAVs for cryospheric research have been published. However, a holistic review discussing the methodological advancements, hardware and software improvements, results, and future prospects of such cryospheric studies is completely missing. In the present scenario of rapidly changing global and regional climate, studying cryospheric changes using UAVs is bound to gain further momentum and future studies will benefit from a balanced review on this topic. Our review covers the most recent applications of UAVs within glaciology, snow, permafrost, and polar research to support the continued development of high-resolution investigations of cryosphere. We also analyze the UAV and sensor hardware, and data acquisition and processing software in terms of popularity for cryospheric applications and revisit the existing UAV flying regulations in cold regions of the world. The recent usage of UAVs outlined in 103 case studies provide expertise that future investigators should base decisions on.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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
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Cited By (since 1996):47, Export Date: 1 December 2013, Source: Scopus
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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.
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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.
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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.
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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.
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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.