THE RESEARCH OF TRANSECT-BASED THREE-DIMENSIONAL ROAD MODEL 
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Tang Luliang 
Li Qingquan' ^ 
| R&D Center of Spatial Information and Network Communication, Wuhan University , Wuhan 430079, China — 
tl wtusm.edu.cn 
2 State Key Lab. of Information Engineering in Surveying! Mapping and Remote Sensing, Wuhan University, Wuhan 
430079, China —lqq@wtusm.edu.cn 
Commission PS WG V/2 
KEY WORDS: GIS, Modelling, Sampling, Virtual Reality, Three-dimensional, Transect-based Road Model 
ABSTRACT 
With the rapid development of 3D GIS, especially Computer Graphics!” Simulation and Virtual Reality, 3D GIS is applied in many 
fields (Li Deren, 2000). On the base of study the road elements and the existing three-dimensional road data model, such as the 
standard road flight in the MultiGen Creator and the TIN-based partition model(Chen Jun, Sun Min, 1999), This paper put forward 
the transect -based road modelling, resolve the modelling of the simplest road with two road transects, and fulfil the visualization of 
the road. OpenGL is applied as the tools of visualization. The map texture technology LjLOD algorithm Li dynamic multi- 
differentiating texture technology are of benefit to the construction of 3D road GIS, and improve the speed of roaming and effective 
visualization. The authors study the combination of the 2D road digital map and 3D road scene, and the dynamic response between 
2D road digital map and 3D road scene. 
Finally, base on the research of the transect-based road model, The authors develop the three-dimensional road geographic 
information system called Virtual Road ( VRoad ), The VRoad does not only supply for road designer a set of tool which can turn 
the designed 2-dimensional road data into three-dimensional road and the high road assistant function area in computer, but also 
supplies for the road management a set of tool which can realize the road real time and interactive roaming, high-efficiency 
managem ent. 
1. INTRODUCTION 
Road plays very important role in the human activities. If 
there are no roads, we can’t imagine what the world be. With 
the rapid development in construction of transportation in China, 
more and more roads have already been running or will be 
going to run, The Ministry of Communications of China claims 
that Chinese road length is the forth longest all of the world. 
Therefore, the more optimizing-ways are demanded to improve 
the road surveying, planning, designing, constructing and 
efficient managing. 
With the rapid development of 3-Dimensional Geographical 
Information System (3DGIS), especially Computer Graphics! | 
Simulation and Virtual Reality, 3DGIS is applied in many fields, 
including the road designing and construction. But the road 
design and management are so complex that 3DGIS is applied 
in a limited task of the road construction. 3DGIS enable the 
road designers to make collaborative and interactive design, and 
provide a tool for the design group to explore many “what if” 
situations quickly, and turn the real-time interactive road design 
into the work. 
Virtual reality applications in road design show great potential. 
For example, complicated road designs can be modelled and 
tested in a virtual environment before construction. VR 
applications can improve the  constructability and 
maintainability of roads and bridges, and also be used by 
designers and builders to better plan and schedule road and 
bridge maintenance operations and efficient management. The 
road three-dimensional Geographical Information System can 
simulate the landscape of the road. During the road driver 
testing and research, many applications have been developed to 
evaluate driver response and the road designing performance in 
computer-generated environments, which make the road 
designers modify their thinking, optimize their designing, which 
  
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Corresponding author, Email: tll@wtusm.edu.cn 
also enable the department of the road management to improve 
their managing pattern and improve the efficiency of 
management. 
2. MODELLING OF ROAD 
The modelling of road elements is the base and precondition of 
road visualization and construction of the road three- 
dimensional system. 
2.1 The Road Elements 
Road elements include terrain, road surfaces, road center 
greenbelt, roadbed, road ditch, road counterfort, road auxiliaries 
(such as road lamp, guidepost, road fencing, road outline sign), 
the buildings ( such as gas station, repair bay, dining-room, 
restaurant, toilet, park ), traffic sign (such as road drive way 
line), road scene ( such as sky, road tree, grass )and so on 
( Figure 1). 
22 The Road Data model and Structure 
3DGIS data model and data structure are the most important to 
express the three-dimensional entities. Many researchers of the 
world who work in the GIS domain have being done lots of 
studies, and progresses has been made, for example, a surface- 
based model, such as grid, shape and NURBS (Harbaugh and 
Merriam, 1968 ); A volume-based model, such as Octree, 
Construction Solid Geometry (CSG) (Samet, 1990), TEN model 
( Pilouk 1994, Oosterom 1995, Chen 1995, Li Qingquan 1998 ); 
an integration of a volume-based and a surface-based model, 
Examples of hybrid models include the integrated CSG and 
  
   
   
   
  
   
  
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
   
   
  
  
   
   
    
   
    
     
  
   
  
  
   
  
    
   
    
   
    
   
   
   
  
    
  
  
      
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