scholarly journals Tree Monitoring Using Ground Penetrating Radar: Two Case Studies Using Reverse-Time Migration

Author(s):  
Iraklis Giannakis ◽  
Fabio Tosti ◽  
Lilong Zou ◽  
Livia Lantini ◽  
Amir M. Alani

<p>  Non-destructive testing (NDT) for health monitoring of trees is a suitable candidate for detecting signs of early decay [1]. Recent developments [2,3,4] have highlighted that ground-penetrating radar (GPR) has the potential to provide with a robust and accurate detection tool with minimum computational and operational requirements in the field. In particular, a processing framework is suggested in [2] that can effectively remove ringing noise and unwanted clutter. Subsequently, an arc length parameterisation is employed in order to utilise a wheel-measurement device to accurately position the measured traces. Lastly, two migration schemes; Kirchhoff and reverse-time migration, are successfully applied on numerical and laboratory data in [3].</p><p>  In the current paper, the detection scheme described in [2,3] using reverse-time migration is tested in two case studies that involve diseased urban trees within the greater London area, UK (Kensington and Gunnersbury park). Both of the trees were cut down after the completion of the measurements and furthermore cut into several slices to get direct information with regards to their internal structure. The processing scheme described in [3,4] managed to adequately detect the internal decay present in both trees. The aforementioned case studies provide coherent evidences to support the premise that GPR is capable of detecting decay in diseased trunks and therefore has the potential to become an accurate and efficient diagnostic tool against emerging infectious diseases of trees.</p><p> </p><p><strong>Acknowledgements </strong></p><p>The authors would like to express their sincere thanks and gratitude to the following trusts, charities, organizations and individuals for their generosity in supporting this project: Lord Faringdon Charitable Trust, The Schroder Foundation, Cazenove Charitable Trust, Ernest Cook, Sir Henry Keswick, Ian Bond, P. F. Charitable Trust, Prospect Investment Manage- ment Limited, The Adrian Swire Charitable Trust, The John Swire 1989 Charitable Trust, The Sackler Trust, The Tanlaw Foundation and The Wyfold Charitable Trust.</p><p>  This paper is dedicated to the memory of Jonathon West, a friend, a colleague, a forester, a conservationist and an environmentalist who died following an accident in the woodland that he loved.</p><p> </p><p><strong>References</strong></p><p>[1] P. Niemz, D. Mannesm, ”Non-destructive testing of wood and wood-based materials,” J. Cult. Heritage, vol. 13, pp. S26-S34, 2012.</p><p>[2] I. Giannakis, F. Tosti, L. Lantini and A. M. Alani, "Health Monitoring of Tree Trunks Using Ground Penetrating Radar," IEEE Transactions on Geoscience and Remote Sensing, vol. 57, no. 10, pp. 8317-8326, 2019.</p><p>[3] I. Giannakis, F. Tosti, L. Lantini and A. M. Alani, "Diagnosing Emerging Infectious Diseases of Trees Using Ground Penetrating Radar," IEEE Transactions on Geoscience and Remote Sensing, Early Access, doi: 10.1109/TGRS.2019.2944070 </p><p>[4] A. M. Alani, F. Soldovieri, I. Catapano, I. Giannakos, G. Gennarelli, L. Lantini, G. Ludeno and F. Tosti, “The Use of Ground Penetrating Radar and Microwave Tomography for the Detection of Decay and Cavities in Tree Trunks,” Remote Sensing, vol. 11, no. 18, 2019.</p>

2021 ◽  
Author(s):  
Hai Liu ◽  
JianYing Lin ◽  
Xu Meng ◽  
Yanliang Du

<p><em>Abstract—</em>Metro traffic in subsurface tunnels is under a rapid development in many cities in the recent decades. However, the voids and other concealed defects inside and/or behind the tunnel lining pose critical threat to the safety of the operating metro tunnels. Ground penetrating radar (GPR) is a non-destructive geophysical technique by transmitting electromagnetic (EM) waves and receiving the reflected signals. GPR has proved its capability in the detection of the existence of tunnel structural defects and anomalies. However, the voids are still hard to be recognized in a GPR image due to the strong scattering clutter caused by the dense steel bars reinforced inside the concrete lining [1]. In this paper, we analyze the propagations of EM waves through reinforce concrete segments of shield tunnels by finite difference time domain (FDTD) simulations and model test.  Firstly, a series of simulations results we have done, indicates that the center frequency of GPR ranges from 400 MHz to 600 MHz has a good penetration through the densely reinforced concrete lining. And the distance between the antennas and the surface of shield tunnel segments should be less than 0.2 m to ensure a good coupling of incident electromagnetic energy into the concrete structure. Then, to image the geometric features of the void behind the segment, reverse-time migration method is applied to the simulated GPR B-scan profile, which presents higher resolution results than the results by using the traditional diffraction stack migration (Figure 1) [2]. Finally, the field experiment results prove that a commercial GPR system operating at a center frequency of 600 MHz do detect a void behind the shield tunnel (Figure 2). The reflection from the void, which starts from the back interface of the segments and lasts over 20 ns, are significantly different from the reflections from the rebars (Figure 3). In summary, GPR has potential in the detection of voids behind the shield tunnel segment. More simulations and field experiments will be performed in the future.</p><p>Keywords—ground penetrating radar (GPR); shield tunnel; voids; reverse time migration (RTM)</p><p>Acknowledgement—this work was supported by Shenzhen Science and Technology program (grant number:KQTD20180412181337494).</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.5ecbddc6f70069664311161/sdaolpUECMynit/12UGE&app=m&a=0&c=eb6a5ae55b4b24b5585021db0e5ca760&ct=x&pn=gnp.elif&d=1" alt=""></p><p>Fig. 1 Numerical simulation of two segments of 2D shield tunnel. (a) numerical model, (b) simulated GPR B-scan profile, (c) migrated profile by using diffraction stack migration and (d) migrated profile by using reverse-time migration.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.659ecbe6f70069964311161/sdaolpUECMynit/12UGE&app=m&a=0&c=07531c033a4f74c3a8e3ac1f5f47316c&ct=x&pn=gnp.elif&d=1" alt=""></p><p>Fig. 2 One photo of the field experiment.</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.d7c12807f70068274311161/sdaolpUECMynit/12UGE&app=m&a=0&c=dd5c073fd4c06a9fd77db502c1d017f2&ct=x&pn=gnp.elif&d=1" alt=""></p><p>Fig. 3 GPR reflections from a void behind the segment of a subway tunnel</p><p>References</p><p>[1]     H. Liu, H. Lu, J. Lin, F. Han, C. Liu, J. Cui, B. F. Spencer, “Penetration Properties of Ground Penetrating Radar Waves through Rebar Grids” , IEEE Geoscience and Remote Sensing Letters ( <strong>DOI:</strong> 10.1109/LGRS.2020.2995670)</p><p>[2]          H. Liu, Z. Long, F. Han, G. Fang, Q. H. Liu, “Frequency-Domain Reverse-Time Migration of Ground Penetrating Radar Based on Layered Medium Green's Functions”, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, vol. 11, no. 08, pp. 2957-2965, 2018.</p><p> </p>


2020 ◽  
Vol 115 ◽  
pp. 102294 ◽  
Author(s):  
Amir M. Alani ◽  
Iraklis Giannakis ◽  
Lilong Zou ◽  
Livia Lantini ◽  
Fabio Tosti

Geophysics ◽  
1992 ◽  
Vol 57 (4) ◽  
pp. 577-586 ◽  
Author(s):  
Elizabeth Fisher ◽  
George A. McMechan ◽  
A. Peter Annan ◽  
Steve W. Cosway

A single‐channel, ground‐penetrating radar (GPR) profile portrays a distorted, unfocused image of subsurface structure due to apparent position shifts associated with dipping reflectors and to diffractions from corners and edges. A focused image may be produced from such data by using any of the migration algorithms previously developed for seismic data; we use reverse‐time migration based on the scalar wave equation. Field work was performed over a simple stratigraphic soil sequence and a complicated fluvial environment. In the migrated images, reflector continuity is enhanced and the level of detail available for high‐resolution interpretation is significantly increased.


Sign in / Sign up

Export Citation Format

Share Document