GPR Data Analysis of Weak Signals and GPR Investigation at Dholavira Site

Abstract

Ground Penetrating Radar is a non-invasive geophysical method used for subsurface investigation. However, GPR often encounters difficulty in visualizing the buried target when signals are weak and enveloped by noise, despite using the best of existing GPR data analysis tools. In this study, new method has been proposed based on Modified S-Transform to analyze weak signals of GPR data. The time-frequency analysis has been implemented to capture the change in electromagnetic waves reflected at the boundary of dielectric contrast. A series of experimental tests were conducted at different site conditions and with different materials using GSSI SIR 3000 GPR system with 400 MHz antenna. An improved 2-D vertical subsurface profile has been developed using time-frequency information to locate the target spatially as well as temporally. The new method has provided better results to improve the target visualization in case of noisy signals. However, it did not add any significant where conventional processing could do reasonable. The proposed method is convenient to use and capable of processing large number of scans effectively. A new area has been explored at an archaeological site of Harappan civilization at Dholavira in Gujarat. GPR survey is done using GSSI system equipped with 200MHz and 400 MHz antenna independently. A wall like T-shape feature is identified which is further interpreted on the basis of the available information about Dholavira. Although the GPR data quality is found to be good, where features were located in conventionally processed profile, however, profiles processed with proposed method has shown improvement in the localization of features and therefore, added confidence in the interpretations of those features.