Diagnosis using ground-penetrating radar (GPR) is an electromagnetic nondestructive evaluation technique. We can apply this technique to highlight the existence of underground cavities in buildings, make it possible to locate areas of greatest weakness, and even avoid potential collapse accidents. The first use of this technique dates back to the beginning of the twentieth century, with the GPR ground-penetrating radar, and like all types of radar, it is based on the emission of a signal and the recovery of an echo. Our main objective of this work is to recover digital data by using the finite time difference domain (FDTD) method; in the first stage, we will simulate a TEz propagation mode in an isotropic homogeneous medium of two dimensions, the second stage is to implement a cavity in the same medium, and study the radargrams recovered from each measurement mode used by GPR radars, namely the common offset method, the midpoint method, and finally the multistatic mode. These data can then be used in other experiments to derive maximum information about the target, that is, its position, size, and even shape.