This goal of this project was to develop a high-resolution millimeter sensor prototype (Figure 1) and demonstrate its use in real time measurements of transverse and longitudinal profiles and micro/macro textures of pavements. The millimeter-wave sensor prototype system was designed, integrated and tested in the laboratory. The compact and low cost sensor was completely realized using millimeter-wave integrated circuits. Laboratory tests produced promising results on the feasibility of the system in mapping surface profiles. In one test, the prototype measured the surface profiles of a metal foil deposited on top of a foam block. The measured contour resembled very closely with the shape of the actual sample. In another test, the sensor system imaged several tiles placed next to each other at different heights. Again, the sensor produced a profile closely resembling the actual surface. The results indicate that the system can map surface profiles with sub-millimeter resolution. The prototype is ready for laboratory and field evaluations to measure macro and micro textures of pavement. However, a redesign of the sensor and a new horn antenna should further improve the performance of the system.
The Texas and North Carolina DOTs have agreed to cooperate and support this development effort, and have expressed strong interest in using the new millimeter-wave system. The Texas Transportation Institute (TTI) will make available its National Skid Resistance test site at the Texas A&M Riverside campus and also the recently constructed TTI roughness calibration facility. These are actual pavement sections with either known surface characteristics or known rut depths. The final report is available from the National Technical Information Service (NTIS # PB2002-103443).