2.1 Automatic Generation of 3D City Models
The material data for the automatic generation system includes
laser profiler data, aerial image, and 2D digital map (Table 1).
With the material data, detailed and accurate 3D city model is
automatically generated
Material data Specification
Laser profiler |-Point cloud data obtained by airborne
data laser profiler, which offers elevation of
terrain and buildings.
-Distance of points: approx. 1m
-Elevation accuracy: 15cm
-Horizontal accuracy: 30cm
-Each point has latitude and longitude
information.
Aerial photo -Digital ^ aerial photo data and
data standardized local coordination
information.
-Resolution: 20-40cm per pixel.
-Vector data based on 2D map of
1/2,500.
-Outlines and attribute data of objects
including buildings, roads, railroads.
2D digital map
Table 1. Material data
The system consists of several programs including 3D city
model automatic generation program, database management
program, material data input program, and 3D CG/VR data
output program (Figure 1).
3D city model automatic generation program, which consists of
several tool programs, generates geometry data of building,
terrain, and overpass and elevated object, using input material
data including laser profiler data, aerial image and 2D digital
map data as input data.
Laser
2D Digital Acrial Profiler
Map Photo Data
3D City Model
Automatic Generation
Program
; Building Model
Data Loading Generation Tool
Program
cS Data for Building Model
/ Generation dition,
Database Editiion Tool
Operation d
Program
Generated Terrain
v Data
3D CG / VR Data
Output Program
Modeling Tool
Overpass
Modcline Tool
Texture Editiion
* Data for Tool
CG/ VR
Texture Data
Figure 1. Program structure of the system
Through the application of 3D automatic generation program,
accurate "geometry model" of terrain and building are
automatically generated. Then, photo-realistic 3D city model
with facade texture on geometry model, which is called
"textured model," is generated (Figure 2). Textured model is
being produced along major roads of major cities with priority.
Presently, geometry model of all major cities of Japan including
Tokyo, Yokohama, Kawasaki, Osaka, Nagoya, Kyoto, Kobe,
Fukuoka, Hiroshima, Sendai and Sapporo are available.
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004
Geometry model of MAP CUBE is revised annually based on
revision of 2D digital map data for car navigation systems.
In addition to geometry model and textured model, 3D models
of well-known buildings/objects, which are called “landmark
models,” are being produced with more detailed geometry and
texture (Figure 3). More than 1,000 landmark models are
presently available.
Ar iC I
d
Figure 2.
Figure 3. Examples of landmark models
(Budoh-kan Hall, City Hall, and Tokyo Tower in Tokyo)
2.2 Application Developments for Virtual Reality
Applications for VR that deal with accurate and photo-realistic
3D city models are becoming indispensable in many fields
including urban planning and navigation. However, there had
been no VR viewer that can appropriately deal with a great
amount of 3D city data in real time.
VR viewer software for popular use on the market has often
difficulties when they are applied for specific purposes in terms
of easy operation or drawing speed. It is also often difficult to
put additional functions in those software It was true too in the
case of displaying 3D city model. In order to solve the problems,
a new VR viewer software that can easily deal with wide areas
of 3D city models has been developed, and it was named
UrbanViewer (Figire 4). It has been available on the market
since 2002.
We eC I
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face of
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UrbanViewer
JrbanViewer provides a variety of functions that are useful and
indispensable in urban design, real estate development, hazard
prevention, urban navigation 3D-GIS and so on.
They include:
-Seamless display of wide area of city
-Fly-through and walk-through
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