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International Archives of the Photogrammetry, Remote Sensin 
g and Spatial Information Sciences, Volume XXXIX-B4, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
most common are flat (Figure 10a), gable (Figure 10b) and hip 
roofs Figure 10c : 
    
  
  
  
Figure 10 Different types of building's roof 
4.6 Building's damage grades 
For identify building's damage grades, the extracted building's 
outlines was registered on the post-event remote sensing image. 
Then visual inspection of building's damage grades was 
conducted. Four damage grades were concerned, slightly 
damage (Figure 11a), moderate damage (Figure 11b), heavy 
damage (Figure 1 1c) and destruction (Figure 11d). 
Figure 11 Different types of building's damage grades 
4.7 Traffic network 
Traffic network is the fundamental geographic data which could 
further used to provide complete road status and damage 
assessment information to emergency operations. In the study 
area, roads are divided into arterial road and secondary road, 
different road type was digitized in different layer with ArcMap. 
4.8 Modeling of Buildings 
3D models allowing decision makers to be more quickly 
recognizing and understanding changes in elevation, pattern and 
features, so they are used for the visualization of disaster risk 
indexes and vulnerabilities to support disaster decision 
processes. As described above, 2D vector building outlines, 
building's roof type, structure material, floor number and 
damage grades could be used to construct 3D textured buildings. 
With the tool of Google SketchUP 6.0 (which enables user to 
quickly create very realistic models of buildings and other 3D 
objects), the models were conducted efficiently. To construct 
textured 3D seismic buildings, building's outlines were firstly 
exported from ArcMap with a geographic reference, models 
were created in SkethchUP next, and then models were 
exported into an ESRI Personal Geodatabase that can be opened 
in ArcScene. For modeling, we firstly extrude building 
polygons by a height value (which calculated with Formula 1.) 
to create realistic building shapes; secondly, we roof was 
construct with its roof type and building's facades were 
textured different with structural materials; thirdly, building's 
roof was colored different with damage grades, as shown in 
Figure 8. 
  
Building floor is the unit object for desired 3D urban model. In 
the study area, maximum floor number is 12 and assumed floor- 
"floor height is 3.0 m. the formula for calculating the height of a 
uilding: 
   
  
   
H,=NxH,, (1) 
Where, H p is the height of building, N „is the number of 
ories and H fif is the floor-to-floor height. 
  
Figure 1. Example of reconstruction of buildings 
4.9 Scene Rendering and 3D Visualization 
Multi-scale 3D visualization is required for disaster 
management due to the need for different details of information 
for different kinds of decisions. For coarse scale, seismic data 
like fault trace and seismic intensity map which are largest 
close to the earthquake are the primary data source for 3D 
visualization, because they concern where the earthquake 
occurs, where is the worst-hit area, where the fault trace, etc. so, 
for 3D visualization of coarse scale, data of fault trace seismic 
intensity map, DEM (Digital Elevation Model), remote sensing 
images should be rendered in the same reference frame, as 
shown in Figure 6. While, for fine scale, building's attributes 
are the primary data source for 3D visualization, and the most 
concerned thing for decision makers is which building damaged 
and how to implement survivors rescue. For this purpose, data 
of traffic network, 3D building models, building's damage 
grade, DEM, remote sensing images were incorporated into a 
GIS environment for decision-making and further disaster 
management. The result is visualized using the ArcScene which 
enables to overlay many layers of data in a 3D environment 
shown in Figure 12. 
Damage Grades 
Slightly 
Moderate 
Heavev 
Destruction 
  
Figure 12: The distribution of seismic damaged buildings in 
Gyégu town in Yushu earthquake 
Figure 12 shows the comprehensive evaluation results of 
seismic damaged buildings in the Gyégu town by using the 
aerial images and damaged building evaluation models. The 
Yushu earthquake causing tremendous damage in the urban 
areas of Gyégu town, Qamdo, etc, killing about 3000 people, 
503