Health Monitoring of Tree Trunks Using Ground Penetrating Radar

Abstract

Ground penetrating radar (GPR) is traditionally applied to smooth surfaces in which the assumption of halfspace is an adequate approximation that does not deviate much from reality. Nonetheless, using GPR for internal structure characterization of tree trunks requires measurements on an irregularly shaped closed curve. Typical hyperbola-fitting has no physical meaning in this new context since the reflection patterns are strongly associated to the shape of the tree trunk. Instead of a clinical hyperbola, the reflections give rise to complex-shaped patterns that are difficult to be analyzed even in the absence of clutter. In the current paper, a novel processing scheme is described that can interpret complex reflection patterns assuming a circular target subject to any arbitrary shaped surface. The proposed methodology can be applied using commercial handheld antennas in real-time avoiding computationally costly tomographic approaches that require the usage of custom-made bespoke antenna arrays. The validity of the current approach is illustrated both with numerical and real experiments.

The Use of Ground Penetrating Radar and Microwave Tomography for the Detection of Decay and Cavities in Tree Trunks

“…Regarding the excitation, a modelled equivalent of the GSSI 1.5 GHz signal, was used [73]. Table 1 shows the dielectric properties of the tree layers used for the numerical simulations, which were derived from the available literature [58].…”

“…Further application examples of these methods are found in other cylinder-like objects, such as columns [63] and tunnel imaging [37]. A similar approach has been put into practice for the evaluation of the internal structure of tree trunks, with encouraging results [31,58].…”

“…Recently, several studies have been carried out on the feasibility of using GPR for large-scale investigations in forestry engineering as well as for the monitoring of tree trunks [50][51][52][53] and root systems [54][55][56][57]. In this regard, the numerical simulation of the GPR signal is relatively recent and it has proven to aid in the interpretation of radar images when assessing the geometric and physical characteristics of trunks and potential decay [52,58,59].…”

Diagnosing Acute Oak Decline Using Ground Penetrating Radar

“…Currently, the most dominant EIDs affecting the European forests are the ash dieback [1], the Xylella Fastidiosa [3] and the acute oak decline (AOD) [4]. AOD is a bacterial infection that can lead to tree mortality within 3-5 years [4] and has rapidly spread in the United Kingdom since its first outbreak in 2012 [5]. Monitoring modern EIDs such as AOD requires new forestry approaches and modern detection schemes [2].…”

“…Monitoring modern EIDs such as AOD requires new forestry approaches and modern detection schemes [2]. To this effect, ground penetrating radar (GPR) has been suggested as a diagnostic tool against AOD [5]. GPR is a non-destructive method that has the potential to detect treedecay in a non-intrusive manner [5].…”