A Time-Domain Finite Difference Decomposition Method for Boulders in the Cultivated Layers Based on Ground-Penetrating Radar

Abstract

Afinite difference time domain (FDTD) model of the electromagnetic wave of the two-dimensional Maxwell's discrete equation is established, based on the optimization of the Ground-penetrating radar (GPR) antenna frequency (recommended 100MHz), time window length, and sampling interval parameters. In our study, three test schemes are designed: The electromagnetic wave enters the boulder medium from the soil to have the first reflection (top reflection) when a boulder point appears in the homogeneous soil, and then passes through the boulder in the water and re-enters the soil. The secondary reflection (bottom reflection) is generated, and radar image interpretation shows that the size of the boulder is the same as the designed size (0.5m).Then, the interference phenomenon of the reflection waves of the two boulders can be simulated when two boulders appear in a homogeneous soil, and the spatial position and size of the two boulders can be distinguished. For the cultivated soil layer with obvious horizontal stratification, the upper soil layer does not affect the reflection of the boulder when the boulder is located in the lower layer, and the location and size of the boulder can still be accurately interpreted. Numerical test results show that the FDTD method is a very effective method to forward simulate the boulder phenomenon in the cultivated soil layer, which has the advantages of simple principle, high simulation accuracy and fast calculation speed.