It is well known in B-scan ground penetrating radar (GPR) imagery that the underground scatterers generally exhibit defocused, hyperbolic characteristics. This is mainly due to the data collection scheme and the finite beam width of the main lobe of the GPR antenna. To invert this undesirable effect and obtain focused images, various migration or focusing algorithms have been developed. In this paper, we survey the performance of our recent focusing algorithms, namely; hyperbolic summation (HS) and frequency-wavenumber (w-k) based synthetic aperture radar (SAR) focusing. The practical usage of these focusing methods were tested and examined on both simulated and measured GPR data of various buried targets. The simulation data set is obtained by a physical optics shooting and bouncing ray (PO-SBR) technique code. Measurements were taken by a stepped frequency continuous wave (SFCW) radar set-up. Scattered C-band field data were measured from a laboratory sand box and from outdoor soil environment. The proposed focusing methods were then applied to the B-scan GPR images to enhance the resolution quality within these images. The resultant GPR images obtained with the proposed algorithms demonstrate enhanced lateral resolutions.
2. Capineri, L., P. Grande, and J. A. G. Temple, "Advanced image-processing technique for real-time interpretation of ground-penetrating radar images," Int. J. Imaging Systems Tech., Vol. 9, No. 1, 51-59, 1998.
3. Yilmaz, O. and S. M. Doherty, Seismic Data Processing-Investigations in Geophysics, Vol. 2, Society of Exploration Geophysicits, 1987.
4. Gazdag, J., "Wave equation migration with the phase-shift method," Geophysics, Vol. 43, 1342-1351, 1978.
5. Claerbout, J. F. and S. M. Doherty, "Downward continuation of moveout-corrected sesimograms," Geophysics, Vol. 37, 741-768, 1972.
6. Schneider, W. A., "Integral formulation for migration in two and three dimensions," Geophysics, Vol. 43, 49-76, 1978.
7. Stolt, R. H., "Migration by Fourier transform," Geophysics, Vol. 43, 23-48, 1978.
8. Cafforio, C., C. Prati, and F. Rocca, "SAR data focussing using seismic migration techniques," IEEE Trans. Geosci. Remote Sensing, Vol. 27, 194-207, 1991.
9. Soumekh, M., "A system model and inversion for synthetic aperture radar imaging," IEEE Trans. Image Processing, Vol. 1, 64-76, 1992.
10. Gunawardena, A. and D. Longstaff, "Wave equation formulation of synthetic aperture radar (SAR) algorithms in the time-space domain," IEEE Trans. Geosci. Remote Sens., Vol. 36, No. 6, 1995-1999, 1998.
11. Gilmore, C., I. Jeffrey, and J. LoVetri, "Derivation and comparison of SAR and frequency-wavenumber migration within a common inverse scalar wave problem formulation," IEEE Trans. Geosci. Remote Sens., Vol. 44, No. 6, 1454-1461, 2006.
12. Anxue, Z., J. Yansheng, W. Wenbing, and W. Cheng, "Experimental studies on GPR velocity estimation and imaging method using migration in frequency-wavenumber domain," Proceedings ISAPE, 468-473，Beijing, China, 2000.
13. Yigit, E., S. Demirci, C. Ozdemir, and A. Kavak, "A synthetic aperture radar-based focusing algorithm for B-scan ground penetrating radar imagery," Microw. Opt. Tech. Letters, Vol. 49, 2534-2540, 2007.
14. Ozdemir, C., S. Demirci, E. Yigit, and A. Kavak, "A hyperbolic summation method to focus B-scan ground penetrating radar images: An experimental study with a stepped frequency system," Microwave Opt. Tech. Letters, Vol. 49, No. 3, 671-676, 2007.
15. Chew, W. C., Waves and Fields in Inhomogeneous Media, 2nd Ed., IEEE Press, NewY ork, 1995.
16. Ling, H., R. Chou, and S. W. Lee, "Shooting and bouncing rays: Calculation the RCS of an arbitrary shaped cavity," IEEE Trans. Anten. Propagat., Vol. 37, 194-205, 1989.