Aerial-Ground collaborative sensing: Third-Person view for teleoperation

Rapid deployment and operation are key requirements in time critical application, such as Search and Rescue (SaR). Efficiently teleoperated ground robots can support first-responders in such situations. However, first-person view teleoperation is sub-optimal in difficult terrains, while a third-person perspective can drastically increase teleoperation performance. Here, we propose a Micro Aerial Vehicle (MAV)-based system that can autonomously provide third-person perspective to ground robots. While our approach is based on local visual servoing, it further leverages the global localization of several ground robots to seamlessly transfer between these ground robots in GPS-denied environments. Therewith one MAV can support multiple ground robots on a demand basis. Furthermore, our system enables different visual detection regimes, and enhanced operability, and return-home functionality. We evaluate our system in real-world SaR scenarios.Comment: Accepted for publication in 2018 IEEE International Symposium on Safety, Security and Rescue Robotics (SSRR

3-D broadband ground-based polarimetric SAR data processing for the monitoring of vegetation growth variations

Subtitle of Symposium: Science for society: exploring and managing a changing planetSAR is usually used for airborne or space borne remote sensing. It can also advantageously be exploited in a ground-based radar imaging system named Ground-based SAR (GB-SAR). We extended earlier approaches and developed an ultra-wideband, ground-based, fully polarimetric SAR (Pol-GB-SAR) system for the monitoring of vegetation growth variations. Measurements on three type trees in different conditions were carried out by the developed SAR system. We proposed effective three-dimensional (3-D) broadband Pol-GB-SAR data processing algorithms in the paper. In situ polarimetric calibration obviously improved the features of the system. 3-D images were reconstructed from the acquired data by a series of signal processing procedures based on a variety of wave equation migration methods. By implementing methods of radar polarimetry, the broadband GB-SAR system has possibility for monitoring changes in tree structure characteristics due to seasonal variations. Interpreted results demonstrated the target scattering characteristics in different vegetation growth situations showed good agreement with the ground truth.http://cat.inist.fr/?aModele=afficheN&cpsidt=1824454

SAR-Based Vibration Estimation Using the Discrete Fractional Fourier Transform

A vibration estimation method for synthetic aperture radar (SAR) is presented based on a novel application of the discrete fractional Fourier transform (DFRFT). Small vibrations of ground targets introduce phase modulation in the SAR returned signals. With standard preprocessing of the returned signals, followed by the application of the DFRFT, the time-varying accelerations, frequencies, and displacements associated with vibrating objects can be extracted by successively estimating the quasi-instantaneous chirp rate in the phase-modulated signal in each subaperture. The performance of the proposed method is investigated quantitatively, and the measurable vibration frequencies and displacements are determined. Simulation results show that the proposed method can successfully estimate a two-component vibration at practical signal-to-noise levels. Two airborne experiments were also conducted using the Lynx SAR system in conjunction with vibrating ground test targets. The experiments demonstrated the correct estimation of a 1-Hz vibration with an amplitude of 1.5 cm and a 5-Hz vibration with an amplitude of 1.5 mm

Potential of ALOS2 and NDVI to estimate forest above-ground biomass, and comparison with lidar-derived estimates

Remote sensing supports carbon estimation, allowing the upscaling of field measurements to large extents. Lidar is considered the premier instrument to estimate above ground biomass, but data are expensive and collected on-demand, with limited spatial and temporal coverage. The previous JERS and ALOS SAR satellites data were extensively employed to model forest biomass, with literature suggesting signal saturation at low-moderate biomass values, and an influence of plot size on estimates accuracy. The ALOS2 continuity mission since May 2014 produces data with improved features with respect to the former ALOS, such as increased spatial resolution and reduced revisit time. We used ALOS2 backscatter data, testing also the integration with additional features (SAR textures and NDVI from Landsat 8 data) together with ground truth, to model and map above ground biomass in two mixed forest sites: Tahoe (California) and Asiago (Alps). While texture was useful to improve the model performance, the best model was obtained using joined SAR and NDVI (R2 equal to 0.66). In this model, only a slight saturation was observed, at higher levels than what usually reported in literature for SAR; the trend requires further investigation but the model confirmed the complementarity of optical and SAR datatypes. For comparison purposes, we also generated a biomass map for Asiago using lidar data, and considered a previous lidar-based study for Tahoe; in these areas, the observed R2 were 0.92 for Tahoe and 0.75 for Asiago, respectively. The quantitative comparison of the carbon stocks obtained with the two methods allows discussion of sensor suitability. The range of local variation captured by lidar is higher than those by SAR and NDVI, with the latter showing overestimation. However, this overestimation is very limited for one of the study areas, suggesting that when the purpose is the overall quantification of the stored carbon, especially in areas with high carbon density, satellite data with lower cost and broad coverage can be as effective as lidar

MMW FM-CW ground-based SAR

This paper presents the design of two ground based synthetic aperture radar (GB-SAR) systems working at 94 and 300 GHz respectively. Frequency-modulated continuous-wave (FM-CW) technique is used for both systems, being described in the first section. Afterwards the first design at 94GHz is presented, explaining its geometry of exploration and describing the architecture of the W-band radar setup. Regarding the integrated receiver system, two models of low noise (LNA) and medium power amplifiers are disclosed, presenting noise figure and S parameters curves comprising frequencies between 75 and 110 GHz (W-band). Finally the second radar setup working at 300GHz is presented, depicting the hardware block diagram and explaining the main performance parameters of the system

Development of a ground-based polarimetric broadband SAR system for noninvasive ground-truth validation in vegetation monitoring

Copyright © 2004 IEEEWe have developed a ground-based polarimetric broadband synthetic aperture radar (SAR) system for noninvasive ground-truth validation in polarimetric SAR remote sensing of terrestrial vegetation cover. This system consists of a vector network analyzer, one dual-polarized antenna, and an antenna positioner. It can be operated in a frequency range from 50 MHz to 20 GHz, with a scanning aperture of 20 m in the horizontal and 1.5 m in the vertical direction. Tests carried out with standard reflectors showed that the polarimetric measurement capabilities of this system are satisfactory. Using the polarimetric ground-based SAR (GB-SAR) system, we carried out measurements on a specific vegetation cover pertinent to the remote sensing of forested regions within Sendai City, consisting of three different kinds of trees common within the Kawauchi Campus of Tohoku University. Measurements were collected in spring, summer, and autumn. Three-dimensional (3-D) polarization-sensitive images were reconstructed from the acquired data. Analysis of the 3-D polarimetric images of each measurement found differences (at times strong differences) among the polarization signatures. There were stronger reflections in all of the HH, VH, VV images in the second (summer) measurement, especially in the VH image, due to the substantial growth of branches and leaves in summer. This ground-truth validation system provided valuable information about the scattering mechanisms of the three trees selected for analysis in different seasons, which can be detected by broadband polarimetric ground-based SAR measurements. The experimental results demonstrate the excellent polarimetric performance of the newly developed SAR imaging system, which should find many useful and immediate applications in noninvasive ground-truth validation of diverse terrestrial vegetation covers.Zheng-Shu Zhou, W.-M. Boerner and M. Sat

A weighted least squares solution for space intersection of spaceborne stereo SAR data

The use of stereoscopic SAR images offers an alternative to interferometric SAR for the generation of digital elevation models (DEMs). The stereo radargrammetric method is robust and can generate DEMs of sufficient accuracy to geocode SAR images. Previous work has shown that ground coordinates with accuracy of four times the resolution cell can be obtained from ERS data without using any ground control points (GCPs), where the high accuracy of the orbit and satellite position of the order of metres introduce insignificant errors into the intersection procedure. The orbit data for RADARSAT is not as accurate as that for ERS, and the perpendicular relationship between the resultant velocity vector and the resultant range vector is uncertain in terms of image geometry. Hence, it is necessary to refine the method to allow for possible errors. This paper introduces a weighted space intersection algorithm based on an analysis of the predicted errors. A radargrammetric error model for observation errors is also formulated to predict the accuracy of the algorithm. The revised method can be used without any GCPs, but this can lead to systematic errors due to less accurate orbit data, and it has been found that the use of two GCPs provides a reasonable solution. The method is insensitive to the spatial distribution of GCPs, which is often critical in traditional methods. The error statistics of the results generated from 32 independent check points, distributed through the entire SAR image, approach the predicted errors and give positional accuracy of 38 m in three dimensions

Pendugaan Cadangan Karbon Di Atas Permukaan Pada Hutan Rakyat Dengan Memanfaatkan Data Synthetic Aperture Radar Sentinel-1 (Studi Kasus Di Kabupaten Sukoharjo)

The high amount of carbon dioxide in the atmosphere is one of the causes of global warming. Preserve carbon stocks is an effort to reduce carbon emissions, including in the community forest which need to be recorded. Remote Sensing Data of Sentinel-1 SAR (Synthetic Aperture Radar) was used to determine the above ground carbon stocks on community forest in Sukoharjo Regency. The objectives of this reasearh are: 1) analyze the relationship between the backscatter value of Sentinel-1 SAR dual polarization data and the value of carbon stock in community forest based on the above ground green biomass value; 2) to estimate above ground carbon stock of community forest in Sukoharjo Regency by utilizing the dual-polarization SAR Sentinel-1 data; and 3) to determine the total and the spatial distribution of above ground carbon stock on community forest in Sukoharjo Regency based on Sentinel-1 SAR data. The method was used in this study is a survey method using purposive sampling to complement remote sensing data related to biomass and above ground carbon stock in community forest using allometric equations based on the the extraction result of backscatter value of each polarization VV (Vertical-Vertical), VH (Vertical-Horizontal), and band ratio VV/VH. Statistical analysis was used to generate equation for estimating carbon stocks based on the SAR data and field data. Geographic Information System (GIS) was used to represent data spatially well as information of above ground carbon stock value and used spatial data analysis approach both quantitatively and qualitatively. The results showed that: 1) there is a significant and inversely relationship between the value of VV polarization backscatter (R = -0.438 (very low)) and VH polarization (R = -0.612 (Low)) on above graound carbon stock value. 2) How to Estimate Above ground carbon stock on community forest in Sukoharjo was obtained from Sentinel-1 SAR data using VH polarization with chosen simple linear regression equation (R2 = 0.375; RMSE = 101.1648) is Y = -61.499 -493.268 + X. The Total of above ground carbon stock in Sukoharjo Regency is 228,456.36 tons of 7738.287 hectares community forest and it has a spread spatial distribution pattern at random and clustered. The largest above ground biomass carbon stock is in the community forest of Bulu Sub-district is 49540.21 tons (1782.008 ha) and least in the Gatak Sub-district is 49.50 tons (1,357 ha)

Imaging SAR phenomenology of concealed vibrating targets

This paper describes the novel imaging of SAR phenomena produced from vibrating targets with multipath effects. It has been established, through numerical SAR experiments, that different physical mechanisms interact to produce new artefacts. The computations demonstrated that the edges of a dielectric medium can act as a source for multipath effects to emanate from, leading to the hypothesis that SAR artefacts can arise from through-wall SAR imagery. This deduction and mechanism of origin were validated through several experimental measurements, undertaken at Cranfield University’s Antennas and Ground-based SAR laboratory, yielding results that closely match those predicted