Recommended CitationBethel, J. S., S. D. Johnson, M. Prezzi, B. H. Van Gelder, B. G. McCullouch, A. F. Cetin, S. Han, M. Hawarey, C. Lee, A. Sampath, and J. Shan. Modern Technologies for Design Data Collection. Publication FHWA/IN/JTRP-2003/13. Joint Transportation Research Program, Indiana Department of Transportation and Purdue University, West Lafayette, Indiana, 2005. doi: 10.5703/1288284313273.
Design data collection involving the use of Lidar instrument, in conjunction with GPS proves to be very effective. Data required to model two bridges over the I-70 was collected on a single day, involving five and six sessions with Lidar equipment. Even though the data was collected on two bridges, it did not cause any disruption of the traffic, either on the Interstate or on the bridges. A major cause of concern during survey activities, particularly along interstates is safety, both for the motorists as well as the people involved in data collection. Lidar data collection was found to be extremely safe in both aspects. The whole process of collecting Lidar data and GPS coordinates for control was completed in 2 days for both bridges. Office work involved combining the GPS data with conventional survey data to bring control on six pre-selected points within the Lidar point cloud. This control information was later used to bring the point cloud into a geographic coordinate system. This survey provided the means to compare the 3D point cloud with bridge designs that were created using other methods of data collection. It was found that the 3D point cloud exhibits a very high degree of accuracy, both internally and also when georeferenced independently using GPS and conventional control survey. The Lidar model was compared to the MXRoad data model provided by INDOT. The discrepancies between the two models were not larger than 0.125 ft/3.81 cm horizontally and 0.05 ft/1.52 cm vertically. The data collected completely modeled the bridge and the accuracy of the data ensures that any model of the bridge, either as a whole or in part, will correctly reflect the current state of the bridge. The data collected can also be used for various applications including cut-and-fill estimates, modeling the state of the bridge, making measurements on various parts of the bridge. A cause of concern is the amount of data involved. As millions of 3D points are collected, popular CAD/GIS packages are unable to deal with it. For this reason proprietary software, designed particularly to handle such huge volumes of data involved, was used for analyzing this data. However, it is possible to export data from this software to other commonly used CAD packages. Using satellite imagery instead of aerial photos may provide faster results to investigate the project area. Conversion of the MXROAD data into the ArcGIS system is not easy, but it is hoped that this problem can be solved very easily. The Lidar point cloud should be processed and a CAD model of the data should be obtained to obtain more useful information. With the help of the GIS a variety of data sources and types can be integrated, visualized and used to make about resource management, and perform modeling and analysis. GIS helps organize bridge management information contained in various forms, such as inspection reports, rehab plans, and CAD files. Maintenance management and asset valuation may be enhanced with GIS and linear referencing systems.
Lidar, GPS, GIS, Satellite Imagery, Control, Design Software, SPR-2450
Joint Transportation Research Program
West Lafayette, IN
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