International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004
two-dimensional in general. Today’s technology development
enabled GIS users to render very complicated and rich
detailed simulations of various environments over the internet
in an easy way of interaction and understanding that is not
currently present in many simulation models. Exceptional than
others, GeoServNet, provides this ease. GeoServNet, is a
2D/3D web-based GIS package developed by York University,
GeoICT Lab. It generates 3D models that can be used as a
comprehensible interface for querying features, hyper-linking
web-based information, for analyzing and visualizing model
results, and accessing different simulation models.
Furthermore, the addition of a third dimension to our
knowledge base of modeled features allowed GeoServNet to
greatly enrich the simulation capacity of predictive models,
which are very crucial for emergency preparedness
applications.
2. 3D VISUALIZATION FOR EMERGENCY
PREPARDNESS
2.1 Types of Visualization
Much of GIS contribution to Infrastructure Protection and
Emergency Preparedness could be addressed at different levels
and in various interconnected applications. GIS visualization
mainly focuses on two domains: computer graphics and GIS
data. Because of interconnections between the two domains, it
is not difficult to integrate techniques exploiting the two
respective domains in terms of 3D application. However, by
reviewing the recent advances in GIS technology, particularly,
web-based GIS, it is found that visualization and rendering
techniques have the largest usage. These developments in
visualization models are in the following areas: a) interpretive:
where the user is basically a “reader” who is attempting to
extract the meaning of the data by visualization. b) Expressive:
In expressive modeling, the user is an “author” who is
attempting to convey the meaning of the data through
visualization, and c) Interactive: where the user integrates both
interpretive and expressive models to generate and extract the
meaning. Interestingly, GIS modeling combines the three;
nevertheless it always depends on the perspective of the
recipient.
2.2 3D Web-based GIS Visualization requirements
Van Driel (1989) recognized that the advantage of 3D lies in
the way we see the information. The real contribution that 3D
web-based GIS present for Emergency Preparedness comes
from its special characteristics. Simply, the purpose of
interactive web-based visualization is to provide smooth
navigation through large 3D GIS models. There are basic
requirements of the visualization process in order for it to be
used as the basis of the GIS client's user interface. It is very
necessary for us to have 1) Display quality 2) Stable network
and system performance 3) Modeling Efficiency 4)
Interoperability that allow for data and system capabilities
share with others 5) Reliability to the level that permits of
having continued analysis. 6) Security, that prevents from
undesired intrusions.
Some of the 3D web-based GIS visual models for users
Infrastructure Protection and Emergency Preparedness include,
Governmental/municipal authorities require tools to perform
administrative tasks (including traffic planning, disaster
preparedness etc.) more efficiently. 3D models also help to
improve public participation in a decision making process.
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Figure 1 showing some applications of 3D Visualization
Integration
3. CASE STUDY
Santa Barbara lies on the West Coast of the United States, 148
km north of Los Angeles and 534 km south of San Francisco. It
is the largest city in Santa Barbara County. Santa Barbara gains
special importance due to the distinguished topography of its
region. It as well falls in a seismic active zone, which puts it
under earthquake risks.
Figure 2 showing study area
3.1 Datasets and Scenario
Vector datasets represented by obstruction layers. Raster data
sets in the form of LIDAR imagery and a Digital Elevation
Model (DEM) were used for conducting this analysis.
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