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Advances in the use of the Short-Time Fourier Transform for assessing urban trees’ root systems

Urbanisation often leads to the destruction of green areas in the urban environment. To this extent, urban trees help mitigating its detrimental effects, as well as offering a variety of socioeconomic and environmental benefits. The presence of root systems in built environments usually results in structural damage, as for example shrinkage of expansive soils due to water suction by roots, resulting in subsidence and fissures in foundations, or roots obstructing pipes and sewers and damaging roads and pavements. Ground Penetrating Radar (GPR) has been extensively used in various areas of civil and environmental engineering. Research has focused on implementing 3D algorithms and investigating root density, and a recent experimental research examined the feasibility of a novel tree root assessing methodology, that processes GPR data both in time and frequency domains. The aim of this research is to improve upon the above-mentioned data processing algorithm, investigating the variation of the frequency spectrum of the GPR signal in urban tree root systems’ surveys by means of a Short-Time Fourier Transform (STFT). Results proved the viability of the methodology and paved the way to further developments for the investigation of urban trees’ root systems using GPR.