International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004 
  
enhancement of the space quality is the origin at the genesis and 
still be the kernel problem of urban design until now. There is 
another famous word of Barnett: Design the city, not design the 
building. "Unlike architecture where the concern is primarily 
with the construction, appearance, and internal organization of 
buildings, urban design relates physical arrangements of 
buildings and streets to functional organization which in turn 
reflects the social and economic structure which makes the built 
environment function or dysfunction." (Batty M, 2000) 
In the history of urban design development, Camillo Sitte is the 
first researcher to insist upon the three-dimensional study of 
city form. In his famous work: City Planning According to 
Artistic Principles. He believed that the designers of cities must 
consider three-dimensional urban form. His work was 
influential in shifting the design of cities from engineers to 
architects. "Though planning was concerned with many things, 
the physical form of the city was a central concern 
“ (Langendorf R, 1999). The urban designer take the urban 
space environment as the mainly design object. 
In fact, all the effort of the architects and planner is to construct 
a pleased, comfort, and efficient space. People always think that 
they plan the city, design the physical form of the buildings, 
actually they use the space formed by the building entities, 
whether inside space or outside space. That is the reason why 
the urban designers take the urban space as their design object. 
Eliel Saarinen thinks that urban design is the art of 3D space 
organize (Saarinen E,1943). Now Urban design has no longer 
simply been taken as the organizational art of geometric space, 
the human life and the social meaning contained by the urban 
space has been recognized more and more, but as the media of 
the human city life, urban space is the major research object of 
urban designer all along from the beginning to now. The spatial 
analysis is very important for planner and designer, but there is 
no any efficient way to control and design the urban space until 
now. 
2.2 The Existing Problem 
Although urban design is a practice process needs much 
detailed and multi-dimensional description, however the urban 
designer can only analyze the urban space with script and 
imagination in the past, and only the urban design guideline and 
some drawing picture were carried out in the traditional design 
project. With the traditional design tools, we can only find the 
problems firstly, analyse the space with the sketch, put forward 
the scheme, visualize the design result through the 2D map or 
picture. How to improve the quality of urban space effectually 
and to express the design schema perfectly are the problems 
troubling the urban designer for a long time. 
Urban designer and architects need to represent and 
communicate their viewpoint in a proper way. In the same way, 
urban manager want to control the urban space efficiently; the 
owner or the stakeholder of course want to communicate with 
the designer without any obstacle; for most of citizen, they look 
forward to know the plan or the design process and participate 
in it conveniently. All these also need a multi-dimensional 
environment, but the true 3D space or 4D space (to consider the 
dynamic change) can't be expressed and designed in 2D plane 
because of its multi-dimensional characteristics. That is the 
reason why the 2D GIS has been used in urban planning field 
for so long time while urban design hardly have any new 
application in this domain. For urban planner and the urban 
designer, the development of 3DCM just can make up the lack 
of traditional GIS. 
Lo 
Urban visualization is proved to be a valuable tool for designers 
and planners. The 3D city models based spatial analysis gives 
the possibility of solving these problems. Comparing with the 
traditional applications of 2D GIS in urban plan, the 3D city 
models based 3D spatial analysis would be more meaningful for 
the urban designer. 
3. THE THEORETICAL FRAMEWORK OF THE 
APPLICATION OF 3D CITY MODELS 
Instead to be described with some adjective words, the 
designing schema and rules can be presented and analysed in 
3D virtual environment. There is three evaluate principles for 
the urban space quality: comfort, pleasant to the eye, and 
convenient. The range of urban space study is so great that it 
can be classified into three aspects based on the three principles 
mentioned above: 
3.1 Physical Quality Analysis of Urban Space 
The physical quality analysis decides the comfortable degree of 
the people's sense. The noise environment, sunlight condition, 
heat environment, ventilation condition, and pollution condition 
could be analyzed through the physical quality analysis. 
In 2003, the HK news media reported that the reasons why the 
Taoda Garden residential area break out SARS, one of reason is 
the poor ventilation condition, especially the “wind curtain" 
between the tall buildings. It was discovered through the 
airflow dynamics analysis in computer by Pro. J.Y.Zhou of the 
Chinese University of Hong Kong (CHUK, 2003) This 
research suggests that the physical quality analysis of urban 
space may often have a social impact on the human life. The 
arrangement and properties of the buildings and the urban space 
around us could control our behaviour. 
Based on the 3DCM, we can choose any date and get the 
sunlight time of any place on any building of a day (sunlight 
analysis), for example, the windowsill of the first floor. If the 
sunlight time below the set time, this building will be 
highlighted and show the lacking time. Especially, we can see 
the dynamic change of the building shadow in the range of time 
set, thus the sunlight condition can be evaluated in 4D 
environment as shown in Figurel. 
    
Figure computation of building shadow 
Another potential application of 3D city models is the 
ventilation analysis. With the merge of more and more 
skyscraper, the ventilation problem appears. Minus pressure 
behind the windward of tall building is good for the inside 
ventilation, but for outside it would make people discomfort 
especially in cold winter. The more the tall building has, the 
more complex the airflow is. How to compute the airflow 
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