ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001
285
(GIS-OT)
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transportation. The basic transportation data-sharing model is the
core model of sharing of ocean transportation information. It
includes common features of ocean transportation data. But it is
not a large integrated data model, it is a seed model which can be
extracted and extended conveniently in data, data structure and
data type (it is not include the basic data structure and data type).
This model is an object-oriented data model. Due to the
differences we talked above, especially the second and the third
differences, we establish some intermediate components to
derive data from basic data model. With the derivation, we
achieve dynamic extension for the basic data model and form the
new chart for application. In derivation, we adopt the standard
rules of information generalization and some intelligent data
extraction and mining technology, such as Artificial Intelligence,
Rough Set, etc. to satisfy the consistence of derivation. These
functions are carried out in Data Extension Model.
2.2 Distributed Computing
In ocean transportation field, transportation decisions supported
by GIS-OTs must often be made by many stakeholder groups
who are distributed both geographically and socially, such as
ocean transportation monitoring and management departments,
ship companies, ships, etc. In addition, stakeholder groups are
often located in different tiers of the administrative hierarchy. Data
providers and users may also be distributed. They use different
sophisticated software to process GIS-OT data. Different
departments have different demands to GIS-OT and use different
combinations of computing and analysis models. We cannot
satisfy so many differences if we still use traditional approach (All
data and computing models located in server, users send their
demands through client to server) to deal with transportation
information.
With the development of Web technology and considering the
differences and the balance of network workload, we should
adopt distributed computing approach. All data, computing
models and analysis models of GIS-OT (all computing models
and analysis models must be separated into independent
function components, which cannot be divided more and each
component can achieve a basic function of ocean transportation)
are maintained by their own providers, ocean transportation
decision makers, users, etc. and located in distributed servers.
But these separated data and models are not messy and
disordered. Their locations and usages are ruled by a uniform
standard of Computing And Analysis Cooperation Service.
Different users send their request to computing and analysis
cooperation service, the service returns the appropriate
combination of computing and analysis models based on user’s
request, and organize data from distributed servers to get the
request results.
2.3 Acquisition And Integration Of Real-time Information
One of the most important features of GIS-OT is real-time. The
main research object in GIS-OT is voyaging ship; go further and
say, is ship features of each ship and all kinds of statistical results
of all voyaging ships. But the information are changed each
minute, even each second, in other words, is real-time. The main
characters of real-time data are mass and messy. And different
department have different demand to real-time data. For example,
ocean transportation monitoring and management department
only need statistical historical ocean transportation data every
day, every month or every year to analyze, make decision and
plan, but a single ship may need real-time data of its own or other
ships every second to make decision when it in emergency. Thus,
there are mainly three problems to deal with real-time data. First,
real-time data is mass data, and was collected from many land
sensors and ship equipments that are geographic distributed. But
the bandwidth is limited. Second, because real-time data were
collected from different sensors, they have different formats. The
third, different land sensors and ship equipments give different
data accuracy, some data very accurate, but others are not. On
the whole, how to establish quicker access data models, more
powerful spatial data fusion techniques and dynamic routing
algorithms to storage, retrieval, processing and analysis are
bottleneck to deal with real-time data of GIS-OT.
In GIS-OT, for each different kind of sensors and ship equipments,
we rectify the equipment error of real-time source data through
special error correction function integrated in Real-time
Information Error Correction Service. And we also provide
different data transform functions for different kinds of data
acquisition sensors and equipments in Real-time Information
Acquisition Service. Through these data transform functions, we
transform different data formats into standard of GIS-OT and
stored in local database as a distributed server cooperated by
Computing And Analysis Cooperation Service.
3. BUILD INTERNET-BASED DISTRIBUTED GIS-OT MODEL
In general, Internet-based distributed GIS-OT mainly consists of
three parts: Background Ocean Transportation Information
(Including geographic information, navigation information and
other data), Basic System of Geographic Information for Ocean
Transportation (The basic parts of Ocean Transportation System,
which includes the basic functional components), and
Applications to different users. Considering the Browser/Server
architecture, network balance of front-end system and
background service, and the features of ocean transportation,
distributed GIS-OT can be divided into several keys functional
parts described as follows. The general architecture of GIS-OT is
shown in Figure 1.
3.1 Data Service
This service is the basic service of GIS-OT, it includes all data
models to storage and process ocean transportation data from all
different sources:
• Basic Data Sharing Model: This is the core data model; it
represents the basic elements of ocean transportation and
can be extended.
• Data Extension Model: Through this model, we can extend
Basic Data Sharing Model to satisfy the development of
ocean transportation.
• IHO-S57 International Transmit Standard Model.
• Real-time Information Acquisition Service: This service
obtains real-time data from different sensors, and
transforms them into standard model.
• Real-time Information Error Correction Service: This
service rectifies the equipment errors of different real-time
source data.
3.2 System Service
The system service provides background service for GIS-OT, All
its models are independent of application, satisfy the demand of
distributed computing environment, and manage the distributed
system. It includes:
• Security Management: This service satisfy multi-users
request in distributed environment and manage access
privilege of different user to guarantee the security of
GIS-OT.
• Metadata: Metadata provides more efficient approach to
search and use distributed ocean transportation data, and
aid to assign and balance the data and operation.
• Event Management: This service deal with the request to
different component.
• Data Connection: This service provides a unitary access
interface for heterogeneous data.
3.3 Computing And Analysis Cooperation Service
This service is the core service of GIS-OT. It includes all
components about computing, analysis and statistic model of
ocean transportation information, and achieves the common
functions of GIS-OT. The main functional components of
Computing and Analysis Cooperation Service are:
• Cartography Service: Different departments provide ocean
transportation information to system through this service.
