Comparing Interpolated Data of Sonic Tomograph and Ground Penetrating Radar to Characterize Tree Roots in Urban Environments

Background Urban afforestation is widely recognized for providing numerous aesthetic and functional benefits to both the population and the environment. However, poor planning ranging from improper species selection to inadequate tree management can lead to various issues, including accidents caused by falling trees. These incidents often result from root failure, underdeveloped root systems, or advanced tree degradation. Methods To evaluate a tree’s root system, indirect methods are recommended, particularly in urban environments with sidewalks or pavements. Techniques such as sonic tomography and ground penetrating radar (GPR) each have their own advantages and disadvantages when applied to urban trees. This study aimed to assess and compare qualitatively the use of sonic tomography and GPR to characterize the root systems of 5 trees located on a sidewalk and in a square. Additionally, a new visualization approach for tomographic data is presented, using kriging interpolation of velocity and error values. Results The results established a qualitative relationship between the high velocity zones detected by tomography, indicating root presence, and the roots mapped by GPR. The new visualization of tomography data provides better opportunities for clearer interpretation together with information of measurement errors. Conclusions Sonic tomography and GPR both assess trees roots in urban environments, but sonic tomography is faster for mapping the extent of root coverage, whereas GPR provides a more detailed characterization of the root system’s spatial distribution, depth, and diameter of coarse roots.