Assessment of Construction Points for Grade Control and Reference in 3D

2019Final; July 2016 - January 2019PDFTech ReportFHWA-GA-19-16180015155Best practicesCase studiesDronesQuestionnairesReferencingRoad constructionSurveysConstruction pointsgrade control3DUAVTLSroad constructionGeorgiaUnited StatesGeorgia. Dept. of TransportationCho, Yong KwonPark, JisooGeorgia Institute of Technology, Office of Performance-Based Management and ResearchGeorgia. Department of Transportation. Office of Performance-Based Management & ResearchUnited States. Department of TransportationUnited States. Federal Highway AdministrationUS Transportation CollectionThe objective of this research is to investigate the causes of inaccuracies of grade elevations from current practices and identify best practices for grade control and referencing on transportation infrastructure construction projects in Georgia. A nationwide questionnaire survey was conducted with contractors, engineers, surveyors, and owners, and the following causes of the discrepancies are identified: (1) long time gap between design and construction phases; (2) poor techniques in surveying; and (3) long interval between survey points. Through an actual case study with an ongoing highway construction project, the following conclusions and recommendations are made: (1) a mandatory field survey before earth moving is recommended; (2) unmanned aerial vehicle (UAV) and Mobile Mapping System (MMS) are effective for 3D grade control in planning and site cleaning phases; (3) terrestrial laser scanning (TLS) is appropriate for 3D grade control in a subgrade grading stage; and (4) robotic total station (RTS) is recommended for the final grading stage.78