Dynamic calibration of radio pulses in horizontally and vertically varying media: an analysis of the problems of radar data collection at speed

It is well established that radar signals used in an echo sounding mode can be used to measure travel times through, and therefore the thickness of, layer of solid media, providing that the velocity through the medium is known: the specific advantage of using this technique is that it is noninvasive, can be operated from one side of the material, and requires neither mechanical contact nor surface preparation. It therefore offers itself as the ideal technique for measuring the thickness of road pavements, at speed in the traffic flow. However, some form of calibration of the sounding velocities is necessary. For the purposes of this paper the whole question of how thick a road is and how an absolute value of that can be assessed is laid aside and it assumed that such a figure is available. The interest lies in the way the calibration systems themselves work, and interact with the pavement being studied. Three separate solutions or techniques of calibration are examined