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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV. Part B2. Istanbul 2004
2. JAVA, WIRELESS LOCATION AND
COMMUNICATION TECHNOLOGY
The Platform is created using Java and leverages object-
oriented principles to realize advantages in maintenance and
ease of integration for third-party developers. It offers two-way
communication and control capabilities in conjunction with a
widespread cellular network and remote intelligent sensors.
Users have access to assets through the Internet.
2.1 Java
Java is a software development platform that was released in
1995 and offered the following benefits:
e The ability to write code once and have it run on multiple
hardware and software platforms with minimal effort
e Designed object-oriented
principals
e Better inherent security and safer memory management
compared to the C/C++ programming languages.
e Allow full-fledged applications to run completely within
an Internet browser
* Developing server-side applications for dynamic and
interactive Internet content
* Usable on a wide range of consumer devices
from the ground up on
Java has especially become popular in the creation, serving and
presentation of content through the Internet and for Internet
enterprise applications. Three Java technologies, namely
Applets, Servlets and Java ServerPages, have features that are
especially useful for the serving and presentation of asset data
to users in a MAMS and are used in the Platform.
2.1.1 Java Applets
An Applet is a Java application designed specifically to work
within the confines of an Internet browser. An Applet is used
whenever complex or graphical information needs to be
presented as it has all the capabilities of a Java application, such
as a graphical user interface. However, as the Applet runs on
the remote user's computer, it is a client-side process and is
therefore barred by Java security practice from accessing
resources on the server directly. To get access to these
resources, some application must be available on the server that
can respond to the Applet's request and provide it with the
resources it needs. For this task, the Servlet is used.
2.1.2 Java Servlets and ServerPages
A Servlet is also a Java application, but one that resides on a
server and listens for requests from the outside. Potential
requests could be initiated by Applets. A Java Server Engine or
a fully Java Servlet enabled web server is needed to properly
operate Servlets. The Servlet is designed to primarily handle
multiple short-lived tasks simultaneously so it utilizes child
threads to handle new requests. Creating only a new child
thread, which can share global memory with other child
threads, is much faster and consumes less computer resources
than previous server-side applications. Child threads also have
local variables that are only visible within a thread context, so
that data meant for one client does not go to another client and
do not interfere with each other in any way.
Java ServerPages (JSP) is Java's answer for server-side
scripting. A JSP file is simply a normal web page containing
201
HTML code intermixed with Java source code and has an
extension of JSP to identify it. The JSPs, like Servlets, are
processed by a Java Server Engine and is executed when it is
called by a user. After execution, the results are outputted as
HTML code in place of the Java source code in the JSP anc
sent to the user for display. Because the JSP is a server-side
application, it also has access to all the resources that ar
available on the server-side. The advantage that JSP has over
other server-side scripting methods is that JSP is a true
programming language and allows the full use of the extensive
Java class libraries. Any new development in Java, even if it
has nothing to do with Internet development, is automatically
available to JSPs and Servlets. This greatly enhances the reuse
of software and code. Another advantage is that JSPs are
precompiled and this benefits response time and performance.
JSPs are primarily designed to handle simple dynamic text
content, such as querying databases and returning the results in
a tabular form. Servlets can transfer any form of data to a
requester, including complex class objects containing desired
data. The class is serialized into a binary stream and sent to the
user application, which casts the binary data back into the
original class object and be directly used in the application.
2.2 Intelligent Sensors for Wireless Location and Asset
Data Acquisition
Remote sensors are important tool in MAMS; not only do they
provide the location of the mobile assets but they can also
acquire important data about the assets. Unlike human data
collectors, they are always at the asset and ready to acquire data
at any time and condition. There are several such sensors
available from different manufactures designed for mobile asset
management and could be used by the Platform. However, in
this paper, only the Asset-Link sensors from CSI Wireless will
be discussed. Asset-Link sensors has been used with a
prototype system, which will be discussed in Section 4, to
combine cellular communication, GPS technologies and greater
“intelligence” to create a fully integrated yet low-cost sensor
that is highly suitable for mobile asset management.
Asset-Link sensors are an intelligent and fully autonomous
location and data acquisition system developed specifically for
mobile asset management applications. Asset-Link sensors
utilize an onboard high-sensitivity GPS receiver chip to provide
location data and data transmission through Aeris MicroBurst.
Not only does the Asset-Link acquire data, it can also be pre-
programmed to perform operations with the asset automatically
or when directed by a command from the asset owner. Because
of its small size, the Asset-Link sensors can be discretely
hidden into vehicles, making it an effective alarm and
monitoring system. Its low power consumption ensures that it
does not detrimentally affect the performance or usability of a
monitored asset, even if the asset is put into storage or is
inactive for weeks or months. [CSI, 2003]
2.3 Wireless Communication
Mobile location and data acquisition sensors from different
manufactures may use different wireless carriers in their
products. The Platform is designed to handle current and future
wireless technologies as they become available and allow users
of the Platform to take advantage of the technologies with little
effort. In the following, Aeris MicroBurst will be described
since it has been integrated with the Asset-Link sensors.
