The Application And Research Of Three-dimensional Entity Modeling In Highway Survey

With the fast development of the computer software and hardware technology, 3D entity modeling technology has been studied and applied extensively in a lot of professions, but there are relatively less research and application in the highway survey. Because the labor intensity is high during field operations of highway survey, 3D entity modeling technology is studied and applied to highway survey, which will translate field operations into inside operations, reduce the labor intensity, shorten construction time and gain a great of economical benefit, so it has an important theoretical and practical value. In terms of the superiority of 3D entity modeling in highway survey, this paper has mainly carried on the research of the following aspects:(1) Data acquisition. At first the band digital topographic map is pretreated, all picture layers are closed except one with elevation points, then 3D Spatial Data is acquired using the secondary development platform of AutoCAD software and VBA language based on selective gather and SQL Server 2000 data management system. The process of 3D Data acquisition is analyzed from the plane diagram of roadbed and the map of vertical and transverse section.(2) 3D entity modeling. Firstly, Digital Elevation Model (DEM) and the side enlarger arithmetic in the arithmetic of triangular irregular networks (TIN) generation are studied. Secondly, the process of 3D entity modeling is researched using the powerful function of 3D entity modeling in AutoCAD software, which is transferring the database and establishing DEM by AutoCAD software and VBA programming language. At last, every triangle is extruded along vertically in AutoCAD, triangular prism is generated, and 3D entity model is built using union Boolean operations.(3) Research on calculation of diagram's basic string. Mutual conversion between coordinates and milepost of arbitrary points is systematically discussed in the different blocks of sectioning route in vertical section (highway's centerline), and determining methods of transverse section are studied in view of baseline, circular curve and transition curve.(4) Mapping vertical and transverse section. On the basis of studying sectioning technique in AutoCAD software, vertical and transverse sections drawing are realized by programming. (5) Earthwork calculation. The grid method and triangular method are studied for calculating earthwork. Then, the fill entity, cut entity and calculation of earthwork are realized based on AutoCAD software.(6) Softwar for mapping vertical and transverse sections is developed, and then development platform, development language, selection of database, and their correlations are analyzed in detail. Finally, a case is study from some highway banding digital topographic map, thus the main functions of the system are verified.