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RECONSTRUCTING ROAD AND BLOCK FROM DEM IN URBAN AREA 
Shoichi HORIGUCHI, Shiro OZAWA, Shigeru NAGAL, Kazuhiro SUGIYAMA 
NTT, Japan 
Cyber Space Laboratories 
horiguti ? marsh.hil.ntt.co.jp 
KEY WORDS: Urban objects, Reconstruction, Modeling, Texture mapping, DEM, Aerial images, GPS 
ABSTRACT 
This paper targets the reconstruction of 3D urban models consisting of realistic architecture models and different objects 
on a ground surface. When reconstructing 3D urban models it is necessary to handle a diverse range of complex 
structures and objects, and the models must be efficiently and precisely formed. Onto these models will be projected the 
textures acquired from the actual objects. Research into building reconstruction has been active, but there is little 
research on structures other than buildings. This paper describes a new approach to reconstructing models for roads, 
intersections and blocks, that is to say, ground surface objects in urban areas. 
When reconstructing road, intersection and block models there are three problems. The first is the separation of roads 
and blocks. The second is the accurate determination of surface model parameters. The third is the construction of the 
optimal model, that is, both the model degree and the model error is minimum Against the first problem, we use digital 
2D maps and separate roads and blocks by matching the edge points of buildings acquired from DEM to the building 
shapes on maps. Against the second problem, we extract only scattered elevation points to avoid obstacles such as 
buildings, trees inside the block and cars on the roads, and determine the surface model parameters by analyzing the 
partial cross sections of roads and blocks, using the MDL principle and heuristic construction knowledge. 
Finally we show an example of 3D urban models of many buildings on a ground surface. Onto these models are 
projected realistic textures. 
1 INTRODUCTION 
1.1 What's 3D urban model 
3D urban model is needed in the fields of urban planning, urban investigation, and urban disaster simulations. Because 
realistic texture is projected onto each model, the 3D urban model is also expected to be used more often in the 
conservation of houses, reproduction of urban views, and forming the Digital City. Moreover, we expect to use the 3D 
urban model as the infrastructure for the Geometric Information System (GIS) in urban areas. This system will build a 
better urban life for us. Examples include traffic control, evacuation guidance, route guidance, and local information. 
For putting these goals into practice we need detailed 3D urban model, especially road and block models, that is to say, 
ground surface models are very important. They make it possible to simulate disaster scenarios such as inundation, 
earthquake, fire, and traffic. By extracting polygonal ground surface models we can project realistic textures onto the 
models to create walkthrough worlds. 
1.2 State of Object Extraction from DEM 
There are two main techniques that realize automatic object extraction for the recovery of 3D urban models. One 
extracts buildings from multiple aerial images (Baillard, C. et al., 1999). The other extracts buildings from DEM 
(Digital Elevation Map) data acquired by airborne laser scanning systems. In recent years laser scanning systems have 
become a very attractive way to acquire 3D data. Especially when mounted in a helicopter, such systems can produce 
high-density height data revealing detailed information about the presence and shape of buildings. By using a helicopter 
we can efficiently and easily acquire 3D data. Compared to the height points determined by matching aerial images, the 
airborne laser scanning systems yield very precise and reliable measurements. Therefore, we utilize DEM data acquired 
by an airborne laser scanning system. 
Several papers have been presented that deal with building extraction from DEM. The pioneers used parametric 
building models and determined the shape and position parameters by fitting the models to the DEM (Haala, N., 1994). 
They also reconstructed prismatic building models with flat roofs using the Minimum Description Length principle 
(Haala, N., 1997). They then utilize the known ground plan information to improve model accuracy. The ground plan of 
a building is subdivided in rectangles. Several models of building primitives are fitted to the height data within each 
rectangle. Merging the models of the primitives using the results of best fitting forms the building models. Moreover, 
they extracted planar roof faces from DEM. In this case, building plans were utilized to determine the orientation of the 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B3. Amsterdam 2000. 413