In coal mining, thickness of thin coal layer is measured for maintaining a defined coal mining horizon. Researchers working in the geotechnical field for detection and thickness measurement of near surface interface address challenges using recent development in radar signal processing. This paper addresses challenge in measuring thickness of thin coal layer left on mine haulage way roof for mine safety. Here, step frequency continuous wave ground penetrating radar (SFCW GPR) signal processing is given for measuring thickness of thin coal layer in presence of interfaces as coal-shale and coal-shale-clay. We use multiple signal classification (MUSIC) algorithm for detecting the interfaces of dissimilar material. In order to improve the resolving power, MUSIC with spatial smoothing process (SSP) and modified spatial smoothing process (MSSP) are applied. Experimental results on thickness measurement using synthetic data models, full wave model (FWM), plane wave model (PWM) and modified plane wave model (MPWM) are demonstrated to compare the effectiveness of estimation algorithms. © 2017 IEEE.