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Stilla, Uwe

' Institute of Surveying and Mapping, Information Engineering University, No.66, Longhai Road, Zhengzhou,
b .
KEY WORDS: Navigation assistant, Mobile devices, Pyramid model, Quad-tree structure, Multi-resolution
Traditional navigation visualization utilizes two-dimensional digital maps for road guidance, and with the advances in visualization
technique, algorithms, and computer hardware, it offer an opportunity of applications for mobile users in 3D virtual environment.
The main challenge comes from how to efficiently provide up-to-data location-specific data and navigation services. For the real 3D
world usually contains a lot of details and represents a huge amount of datasets, so it is a difficult to visualize the complex virtual 3D
scenes and navigate in them on mobile devices. To solve the problem, this paper proposed a novel approach that is based on
geographic web services and the servers dynamically generate the 3D scenes in terms of the navigation commands and then send the
resulting as video-encoded image stream to the mobile client. In order to enhance the efficiency of 3D scenes rendering, those virtual
3D models’ datasets were prepared and organized in an offline process. The approach allows us to provide interactivity for complex
virtual 3D scenes on resource and bandwidth limited mobile devices.
Traditional navigation and trip planning is two-dimensional
map display mode, and user can only accept limited information
organization, poor presentation, and lack of interaction. On the
contrary, applying 3D techniques for realistic visualizations into
navigation fields provides new or better solutions that are
hardly solved by 2D means, the advantages over 2D case are as
follows: 1) easy navigation of the information space allowing
better user interaction with the virtual objects and user can
understand the displayed data through the existence of visual
metaphors better. In contrast, 2D map reading is a skill which
requires specific training; 2) the capability to display more data
at one time, because each location on a 2D map is shown in the
same scale, and users need to change scales in order to switch
from viewing local details to overviews. The perspective view,
on the other hand, has the inherent capability of combining
different scales into one scene by dedicating a larger amount of
the screen to the immediate surrounding while at the same time
showing the entire route in an overview.
Mobile devices, like personal digital assistants (PDAs), mobile
phones, Palm Pilots, or Pocket PCs, have made undreamed
progress in computing power, function of displaying and input
options a few years ago. Combined with a Global Positioning
System (GPS) receiver, the mobile devices offers an
opportunity to interact with a map display showing the current
location and orientation.
Therefore, focused on how to represent 3D environment which
support navigation on mobile devices, this paper presents a
client-server solution for accessing virtual 3D scenes for
navigation. The approach is based on 3D modelling techniques
in which a full 3D model is generated on sever and sends the
resulting as video-encoded image stream to the mobile client.
The solution can be decomposed in three steps. The first one is
pre-processing. The main purpose is preparing data offline. The
second one is 3D scenes rendering. The user controls the client
by navigation command sketches drawn directly on the view-
plane and the sketches are sent to the server, then the server
interprets these sketches in terms of navigation commands, and
generates the 3D panorama scenes. The last one is sends the
results as image sequences to the mobile client.
Mobile applications of virtual 3D scenes represent a major and
complex research challenge and bottlenecks due to limited
bandwidth and graphic capabilities, restricted interaction
capabilities, data standardizations and distribution techniques,
and digital rights issues. The main challenge here is how to
render the 3D scenes and models as to usable navigation task
within the 3D environment because there lack of an efficient 3D
engine and suitable 3D model that would allow such
development and field experiments. And the other challenge for
the navigation domain comes from how to maintain real-time
update rates in loading and unloading large, complex datasets.
In fact, 3D space data obtain from the natural environment is
Institute of Surveying and Mapping, Information Engineering University, No.66, Longhai Road, Zhengzhou, R.P.China. 450052.
E-mail: chxy_wenjiang37@yahoo.cn; kissfro9642@sina.com. Tel: 86-13017690807.