Detecting defects in conifers with ground penetrating radar: applications and challenges

Abstract

Our objective was to test ground penetrating radar (GPR) to non-destructively estimate decay volumes in living coniferous trees. GPR is geophysical tool which uses an antenna to propagate short bursts of electromagnetic energy in solid materials and measure the two-way travel time and amplitude of reflected signals. We compared estimates of bole decay from data collected with a SIR 3000 GPR system equipped with a 900 MHz antenna to measurements of decay from stem cross sections and increment cores for three conifer species (Pseudotsuga menziesii, Thuja plicata and Tsuga heterophylla). We found that near-surface decay, air-filled voids and desiccated boles had unique electromagnetic signatures, which could be separated from other defects. GPR successfully estimated the percent area of air-filled cavities and was not significantly different than results from destructive sampling. However, separation of incipient to severe decay from benign reflectors (e.g. moisture gradient between sapwood and heartwood) in conifers was much less diagnostic than with angiosperms. A limited assessment of Acer saccharum showed that GPR has potential to detect defects in angiosperms; however, more research is needed to outline the full range of detectable defects. Based on the trees in this study, the potential for GPR to detect decay-related defects in conifers seems limited. Despite problems detecting decay, reflections originating from the sapwood : heartwood boundary may prove useful to determine thickness of functional sapwood in conifers, but accurate quantification will require further technical development.

Evaluation of GPR surveys for assessment of trees condition in urbanized areas

“…Examples of studies on discs cut out perpendicularly to the trunk axis (Nicolotti et al 2003), and on root systems (Barton & Montagu 2004, Cermak et al 2000 were found. In literature, one can also find works on the analysis of the electromagnetic wave amplitude used to locate objects' defects (Butnor et al 2009), and the effects of trees scanning using antennas with frequencies up to 1000 MHz (Lorenzo et al 2010). Careful analysis of the literature resulted in main aim of this paper -verification if the GPR method eligible for process of detection internal structure of trees for purpose of eliminating ones with inferior quality and those which can threaten public safety.…”

Forestry applications of ground-penetrating radar

“…As a result, the authors established correlations between GPR data and root biomass, finding an important relation between the root biomass and the reflected energy. The last reference we have found is attributable to Butnor et al (2009), who test GPR to non-destructively estimate decay volumes in living coniferous trees.…”

A Method for Layered Identification of Defects in Trees Using Ground Penetrating Radar

“…In this way, most of radar waves were reflected when encountered a mental plate. Thus, the propagation velocity and the average dielectric constant of trees could be calculated by the two-way travel time in the known distance (diameter trees) [10]. …”