Root orientation can affect detection accuracy of ground-penetrating radar
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Ground-penetrating radar (GPR) has been applied to detect coarse tree roots. The horizontal angle of a root crossing a scanning line is a factor that affects both root detection and waveform parameter values. The purpose of this study was to quantitatively evaluate the influence of root orientation (x, degree) on two major waveform parameters, amplitude area (A, dB × ns) and time interval between zero crossings (T, ns).
We scanned four diameter classes of dowels in a sandy bed as simulated roots using a 900 MHz antenna from multiple angles to clarify the relationships between the parameters and x.
Angle x strongly affected reflection images and A values. The variation in A(x) fitted a sinusoidal waveform, whereas T was independent of x. The value of A scanning at 90° was estimated by A values of arbitrary x in two orthogonal transects. The sum of T in all reflected waveforms showed a significant linear correlation with dowel diameter.
We clarified that root orientation dramatically affected root detection and A values. The sum of T of all reflected waveforms was a suitable parameter for estimating root diameter. Applying grid transects can overcome the effects of root orientation.
KeywordsCarbon storage Coarse root Grid transect Nondestructive root method Root angle Root diameter
Root angle subtended to the transecting lines
Time interval between zero crossings
Sum of amplitude areas for all of reflection waveforms
Sum of time intervals for all reflection waveforms
- Single Amax
Amplitude area of the maximum reflection waveform
- Single Tmax
Time interval of the maximum reflection waveform
We thank D. Nomoto of KANSO Technos, N. Makita and R. Sasaki of Kyoto University, and U. Kurokawa, T. Chikaguchi, S. Narayama, M. Tanaka, and Y. Shimada and the other members of Kansai Research Center, Forestry and Forest Products Research Institute for their help with the field experiment. We additionally thank M. Ohashi for reading a draft of this manuscript. We acknowledge financial support from Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan (No. 22380090, 25252027). This study was also supported by the Program for Supporting Activities for Female Researchers funded by MEXT’s Special Coordination Fund for Promoting Science and Technology.
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