A Comparison of Four Methods for Accurate Ultrasonic Range Estimation

Four methods of range estimation for airborne ultrasonic systems|namely simple thresholding, curvetting, sliding-window, and correlation detection|are compared on the basis of bias, standard deviation, total error, robustness to noise, and the di culty of implementation. Whereas correlation detection is theoretically optimal, the other three methods can o er acceptable performance at much lower cost. Two variations of curve tting and four variations of sliding-window have been considered. Performances of all methods are investigated as a function of target range, azimuth, and signalto-noise ratio (SNR). Curve tting, sliding-window, and thresholding follow correlation detection in the order of decreasing complexity. Apart from correlation detection, minimum bias and total error is most consistently obtained with the curvetting method. On the other hand, the sliding-window method is always better than the thresholding and curvetting methods in terms of minimizing the standard deviation of the estimate. The experimental results follow the simulations closely. Overall, the three simple and fast estimation methods provide a variety of attractive compromises between estimation accuracy and system complexity.