A new method to simultaneously estimate the radius of a cylindrical object and the wave propagation velocity from GPR data

We present a new method to simultaneously estimate cylindrical object radius (R) and electromagnetic (EM) wave propagation velocity (nu) from ground penetrating radar (GPR) data. R estimation methods have been investigated since the middle of the previous decade, but studies have become more intensive and important over the last several years since they increase the utility of GPR data and enable new GPR applications. Since existing methods, according to the author's best knowledge, are based on a priori known nu, the proposed method has an advantage: it eliminates the measurement of nu and its influence on R estimation quality. Estimating nu accurately results in better soil characterisation. Three steps are used to simultaneously estimate nu and R. First, using the extracted raw data, the coordinates of the hyperbola apex (x(0), t(0)) are estimated. Second, the boundary speed (nu(0)) is estimated, based on the previous results. In the final step, nu is reduced from nu(0) to a predefined nu(min). From the analysis of propagation velocity choice criterion, an optimal nu is chosen, which is used to calculate a unique R. This proposed method is a nonlinear least squares fitting procedure. The method is implemented and verified, using data collected under real conditions, in a Matlab environment. A comparison of the proposed and existing methods shows that the new method is significantly more accurate and robust with regard to noise and the amount of raw data. (C) 2009 Elsevier Ltd. All rights reserved.