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In this work, a novel signal processing framework for polarimetric GPR measurements is presented for inspection of tree trunks decay. The framework combines a polarimetric noise filter and an arc-shaped diffraction imaging algorithm. The polarimetric noise filter can increase the signal-to-noise ratio (SNR) of B-scans caused by the bark and the high-loss propriety of the tree trunk based on a 3D Pauli feature vector of the Bragg scattering theory. The arc-shaped diffraction stacking and an imaging aperture are then designed to suppress the effects of the irregular shape of the tree trunk on the signal. The proposed detection scheme is successfully validated with real tree trunk measurements. The viability of the proposed processing framework is demonstrated by the high consistency between the results and the real-truth trunk\ud cross-sections.

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.\ud 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.

In this work, the novel imaging algorithm of synthetic aperture radar (SAR) system to be used in near-range based on fractional Fourier transform is presented. The algorithm projects the target reflectivity function onto pseudopolar coordinates and focuses along the short time through the fractional Fourier transform. The discrete format procedure for imaging near-range target is also introduced in this paper. The numerical simulation results show that the algorithm is more suitable for the high-precision synthetic aperture radar imaging in the near field.