Evaluation of laser scanning technology for bridge inspection

In United States, there are almost 600,000 highway bridges. The average life time of these bridges is about 70 years. When bridges reach their mid-life, some damages on structures may occur. The prospective causalities for unproductive bridge inspection can cause serious problems. The main purpose of the bridge inspection is to satisfy the public safety in bridge structural capacity and to protect the public investment. All these emphasize the importance of the accurate and reliable geometric information of the bridges. Geometric data, such as maximum span and minimum vertical clearance are the main parameters of bridge inspection process. All these challenges highlight the importance of terrestrial laser scanner for bridge inspection. Laser scanner is a reliable technology for geometric data collection. Although laser scanners enable surveyors to acquire the data in shorter time, data accuracy should be investigated. The main objectives of proposed study are to investigate and evaluate the accuracy of laser scanners for bridge inspection and to determine the reliability of laser scanners data. The objective of the proposed study was to investigate laser scanner data reliability on bridge inspection projects. Based on laser scanner data, specific bridge component dimensions have been measured and a 3D model of the bridge was created. On the field, the laser scanner was set up on four different locations and captured the bridge substructures data. The office work consisted of registering different point clouds from individual scans together into a single coordinate system. By using registered point cloud, a 3D model of the bridge was created. Afterwards, dimensions of substructure components of the bridge were measured and compared with design drawing data. As a result, error ratio of the compared results is mostly under 1% aside from some irregular conditions at the edges. Comparisons showed that the scanned data is reliable in terms of accuracy. Also data acquisition is faster and data density is much higher than other surveying methods.