Impulse radar for the investigation of pavements

This paper describes research carried out to develop new techniques to meet the needs of today´s pavement engineers. Impulse radar can be utilised to perform various road investigation tasks. The two most popular being (1) problem solving e.g. investigation of the sub-surface to find the causes of subsidence; and (2) inventorying the road network. Task (2), until traffic speed surveying was possible, was not practical due to the large range of data collection required. Using the ALPS system (Automated Layer Profiling System) impulse radar data can be collected at traffic speed sampling the pavement at 250 mm intervals which is comparable to the sampling achieved by the slowly towed systems. Most of the slow systems are analogue systems with the only output being black and white paper charts whereas with the new digital system that are available the data can be recorded in a form ready for processing an a PC. Processing and manipulation of the data has been a major advance in the impulse radar technique, made possible by digital technology and readily available computer power