## 1 Introduction
### Ground Penetrating Radar (GPR)  
Ground Penetrating Radar (GPR) is a non-invasive, high-resolution geophysical method where antennas may be up to a few GHz to produce an image of the subsurface conditions [11]. It has a wide range of applications in the field of civil engineering, such as the mapping of soil layers, detection of buried services, inspection of pavement layers, inspection and quality control of concrete structures, etc. [PERSON] et al. [12] discussed that using parallel profiles can help identify significant differences between the profiles. It was also possible to construct stages of the leak and water dissipation through the soil. Additionally, [PERSON] et al. [13] devoted their research efforts to collect signature images to a water leak, utilizing differences of the dielectric contrast and reflection coefficient at various water injection stages. These images are used to identify water leaks in pressurized water supply pipes or drainage pipes. Another study by [PERSON] et al. [14] focused on using advanced, integrated radar data processing and visualization strategies. They used full-wave inversion to estimate the medium properties, in addition to the removal of near-field antenna effects as well as reflection detection and segmentation algorithms. They also highlighted the importance of 3D images and qualitative data processing strategies that help in detecting continuous objects (pipes) from buried stones. A review by [PERSON] and [PERSON] [15] highlighted that 3D image models are used to provide details about the soil layers, thickness, and volume calculations. However, one of the disadvantages is the time and data acquisition required to build these models. In addition, there have been many experiments conducted on the use of the GPR to detect leaks in water pipes buried underground, as summarized in Table 2. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Study Type** & **Soil** & **Pipe Material** & **Pipe Diameter (mm)** & **Results** & **Reference** \\ \hline Lab & Dry soil & PVC & 100 & \begin{tabular}{c} GPR was successful in not only detecting the \\ leak but also reconstructing the various stages \\ of the leak and how water dissipated through \\ the soil \\ \end{tabular} & [12] \\ \hline Field & \begin{tabular}{c} Gravel, sand, silt, \\ and clay \\ \end{tabular} & Unknown & - & \begin{tabular}{c} GPR produced inferior results as the presence \\ of clay resulted in absorption of the GPR \\ signals \\ \end{tabular} & [16] \\ \hline Field & Unknown & Unknown & - & \begin{tabular}{c} GPR can be applicable for leak detection of \\ several types of pipes \\ \end{tabular} & [17] \\ \hline Lab & Sand & Metal and PVC & 19 & \begin{tabular}{c} Raw data collected in the field by GPR is \\ sufficient to detect water leaks \\ \end{tabular} & [18] \\ \hline Lab and field & Dry soil & \begin{tabular}{c} Lab: PVC, Field: \\ cast iron \\ \end{tabular} & Lab: 100 Field: 400 & \begin{tabular}{c} Difficult to interpret raw images, more \\ complex models are needed \\ \end{tabular} & [19] \\ \hline Lab and field & Slit and clay & \begin{tabular}{c} Plastic and \\ metallic \\ \end{tabular} & - & \begin{tabular}{c} GPR technique provided a good estimation of \\ the position of the leak; however, its response \\ is influenced by the presence of other buried \\ objects/ anomalies underground \\ \end{tabular} & [20] \\ \hline Lab and field & Dry sand & Plastic & 50 & \
\begin{tabular}{c} Successful but detection through voids highly \\ depends on the investigated medium and the \\ radar system parameters \\ \end{tabular} & [21] \\ \hline Lab & Soil & Cement & 200 & GPR was successful in water leak detection & [22] \\ \hline Field & Slity clay & PVC & 152.4 &
\begin{tabular}{c} The pipe appears slightly deeper in the image \\ above the leak, which could indicate radar \\ waves slowed by saturated soil near the leak \\ \end{tabular} & [23] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Studies using GPR for water leak detection. GPR uses electromagnetic (EM) pulses in the microwave range.