Study On The Principle And Method Of Road Three-Dimension Measurement System

With the development of our highway construction, the traditional two-dimensional measurement technology has been unable to meet the requirements of Pavement Management System, Intelligent Transportation System (ITS) and the increasingly sophisticated pavement evaluation. The three-dimensional road measurement technology is becoming the direction of the future road tests.Pavement measurement technology has developped a process from manual to automatic, damage tests to NDT tests, slow to high-speed, a single index to multi-function tests. Studing the new technology of the 3-D surface detection can not only meet our ever-increasing acceptance of the road quality and conservation needs, but also be important for the development of road evaluation and ITS.Pavement is a three-dimensional body, under the three-dimensional road coordinate system with the profiling be x-axis, cross-sectional be y-axis and the relative height be z-axis, the three-dimensional measurement of road can be simplified to the longitudinal profiles tests or cross-sectional profiles tests.Because of the vibration of the test vehicles, each received cross-sectional has its different baseline. Through a linear correction, the rutting information of the road can be accurate get. But the three-dimensional information can't be derived. Two additional elevation informations of the longitudinal profiles must be introduced with the transverse profiles data to complete the three-dimensional reconstruction.The traditional road profiling tests only contains a wavelength of 0.5 to 80 m, but the real profiling is not only including the micro-texture, the macro-texture, the magi-texture, but also contain the evenness and road lines information. A three-layer-test model including of texture layer, evenness layer and GPS layer is proposed to achieve the entire longitudinal profiles information. Since each layer has its coordinates, detection technologies, accuracy and different information, each coordinate should be changed to a unified road coordinates to add up to a whole profiling by information fusion. A non-inertia principle based on the datum transfer is proposed to solve the question of speed limit in inertia test system. The tests speed has little influence on the result of datum transfer system.By analysis the errors in the cross-sectional detection based on the multi-sensor principle, the error caused by the sampling point inconsistent leads to a random error, and the error caused by the limited accuracy of sensors introduces a system error. When the number of sensors is smaller, the rut error is mainly caused by the inconsistent sample points; when the number of the sensors is bigger enough, the rutting error is mainly caused by the sensor's accuracy. Based on the statistical law of the road rut, a dual-cosine rut model is establishment to estimate the relationship between the number of sensors and the rut measurement error. Computer simulation result shows that when the number of sensors increase to 31, the rut error is reduced very slowly, the biggest error does not exceed 2%.Unlike ordinary reflective objects, pavement has a rough surface, its reflective rate can changes from approximate mirror to zero. By studying the curve of the CCD saturation, a new structure of two mirror systems with reverse CCD direction is given. It gives a good result to elimination the problem of CCD saturation. It can be applied to various roads.Based on the whole spectrum profiling model and three-dimensional road reconstruction model, a platform which contains of 39 laser sensors, 2 based-line GPS, a road optical encoder is established to reformed a three-dimensional surface. A three-dimensional detection Results is given.