level. In order to support the construction of
international tourism island and Digital Hainan
Province, it is required to build Hainan Province
"Digital Ocean" platform to integrate all ocean
environment 3D monitoring data, including sea, land
and air data to support ocean information
visualization and decision-making support. Because
of the complex of ocean data, such as spatio-
temporal, 3D and dynamics, new technical
framework of "Digital Ocean" platform and new
techniques such as multisource spatial data
organization and management and self-adaptive
visualization need to be developed.
This paper introduces the design and
development of Hainan Province "Digital Ocean"
platform, with characteristic of “software, data and
services all-in-one integration” and “dynamic, high-
resolution, automatic ocean information
procession”, and its applications on natural disasters
prevention and reduction.
2 SYSTEM DESIGN
The Hainan Province "Digital Ocean" Platform is an
integrated system that integrates ocean factor
visualization and ocean phenomenon visualization
models, databases, graphical user interfaces, and
ocean information services to help the public and
decision makers for ocean information sharing
(Figure 1). It also can be used for natural disasters
prevention and reduction for forecasting, risk
prediction, and disaster loss assessment of typhoon
storm surge.
This system has a multi-tier architecture
consisting of presentation, business logic, and data
tiers. Figure 1 provides an overview of system
architecture. The presentation tier is the interface for
users to interact with system, users can submit
requests from the presentation tier, and it also can be
used as the system client viewer for accessing 3D
ocean factor and phenomenon visualization
information. The business tier copes with the
requests from the presentation tier. The business tier
has three parts, including spatial database engine and
metadata management, ocean information 3D
visualization model and ocean information services.
The data tier includes all available data sources,
such as basic geographic database, remote sensing
image database, ocean basic geographic database
and 3D and dynamic ocean database. The database
server is used to manage those sharing databases in
this system, and it also supplies data services for the
application server and spatial analysis and model
analysis server.
3 THE CONSTRUCTION OF 3D
VISUALIZATION MODEL
BASED ON EARTH SPHERE
MODEL
As the base of Hainan Province "Digital Ocean"
platform, the construction of 3D visualization model
based on earth sphere model is very important, the
technical realizations are as following: firstly, the
reference datum of earth sphere model is defined as:
the model is based on the 3D coordinate system of
the earth centroid as the original point O, it is a
right-handed Cartesian coordinate system with Z
axis pointing north direction, Y axis is from west to
east, and the X axis is the orthogonal basis of Z and
Y axis; secondly, the Digital Orthophoto Maps
(DOM) is fused with Digital Elevation Model (DEM)
to create real 3D terrain model by project
transformation, geometric transformation (including
pan, rotation, zoom in and zoom out etc.) and
texture mapping using DirectX; then through the
overlay of vector data with DEM and integration of
building model, scene model and facility model with
terrain model to implement 3D visualization model
based on earth sphere model. Finally, navigation
operations such as rotation, pan, zoom in and zoom
out, and spatial query are implemented by using free
Active X in client side.
The construction of 3D visualization model
includes the following 5 steps.