The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008
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abnormal detection appears, the server sends out the detection
signal. And the PC client downloads the newest detection
information from the server through the internet, communicates
with the field client, and disposes the event investigations and
measures. The field client uses the portable digital equipment
(PDA or intelligent cell phone), communicates with the server
and PC client through mobile network, sends back the
investigation data and information to the server, and completes
the emergency response work.
Figure 1. Structure design of collaborative surveillance and
response system
The collaborative server is an internet work station with
powerful computing and storage abilities, employs large
database systems (e.g. Oracle, SQL Server) for the storage of
disease data, runs a full-time epidemical surveillance program,
and with the multi-thread mode and the network protocol,
implements the communication and information transmission
between the server, the PC client and the field client. PC client
has a collaborative operation program and a 3-D visual
surveillance program, downloads the detection data from the
server through the internet, completes the visualization of
surveillance and detection, and provides directly visible effects
about the detection which could help the operators make the
correct and exact decisions. The portable digital equipment of
the field client has a communication program which could
connect to the server and PC client through mobile network,
completes the data collecting and feedback in event
investigation, and meanwhile has a program for event treatment,
which could help the working people finish the emergency
response conveniently and effectively.
5. IMPLEMENTATION OF PROTOTYPE SYSTEM
Prototype system of this paper is developed based on standard
C/C++ programming language. Programs of server and PC
client are developed by Microsoft Visual C++ IDE, and
programs of PDA client are developed by Microsoft eMbedded
C++ IDE. Collaborative server, whose operation system is
Windows 2003 Server Edition, has CPU of Intel Core 2 T5600,
2G memory and 1000M network card. Database system used in
server is Microsoft SQL Server 2000. PC client is common
microcomputer. PDA client is PDA with Windows Mobile 5.
Collaborative server, which is the main part of epidemical
surveillance subsystem, assumes the responsibility of whole
time surveillance, and meanwhile provides collaborative service
for PC client and PDA client. The prototype system uses a
powerful computing and storage server in internet as the
collaborative service, and disposes two services: PC service and
PDA service which are responsible to the PC and PDA clients
respectively. PDA service is a multi-thread program for data
exchange based on Winlnet structure, and is in charge of the
data exchange between collaborative service and PDA client.
PC Service is a multi-thread service program developed with
Socket protocol, and monitors and responds the requests of
computer terminals in specified port. According to the function
demands, PC Service could include terminal computing service,
database service and information service of sending and
receiving. Furthermore, according to the information types
during the information sending and receiving, information
service could be classified into three different types: message
service, text service and file service. The service types and
functions of collaborative server are shown in Table 1.
PC client is the information bridge of collaborative work
between surveillance and response subsystems. When the
surveillance computing results of server terminal appear
exceptions, collaborative server will send exception information
to PC client. And then PC client directs PDA client to perform
emergency response work in exception regions. PC client
builds up the communication connection to collaborative server
and PDA client by Socket and Winlnet respectively.
PDA client accepts the directions from collaborative server and
PDA, provides various functions of response subsystem for the
response personnel to accomplish the epidemical fieldwork
investigation and emergency response, and sends the response
data back. The communication connection between PDA client
and collaborative server is built up on the basis of Http protocol
and GPRS mobile network.
Service Name
Service Function
PDA Service
Collaboration and data exchange
between Server and PC Client
PC
Service
Computing
Service
Terminal surveillance computing
and information exchange of the
computing results
Database
Service
Database server and storage of
geographical and epidemical data
Information
Service
(Send and
Receive)
Message
Service
Information exchange
of messages
Text
Service
Information exchange
of texts
File
Service
Information exchange
of binary datafiles
Table 1. Service types and functions of collaborative server
6. APPLICATION OF PROTOTYPE SYSTEM
The terminal computing program of collaborative server uses
spatial and space-time scan statistics methods, and implements
the real-time epidemical surveillance according to the existed
geographical and disease data. When the exceptions appears in
both spatial and space-time scan statistics, collaborative server