International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B2. Istanbul 2004
Statusbar and Map components are part of the View, as they
help present information and processing results to the user.
For the Web Client, all of the user accessible tools appear to be
part of the Toolbar, at least as seen from the user's point of
view. However, the implementations of these functions are
actually in the Parent Shell. The Toolbar is only used to
activate the proper functions in the Parent Map. The tools that
have been created include typical GIS-type functions for map
viewing and manipulation as well as for viewing and querying
spatial and non-spatial information. These functions interface
with the Data Module and retrieve data from it. Another
category of functions are used for asset control, which sends
user-issued commands to the Relay Server. The type of control
functions. available vary depending on the asset and the
configuration of the onboard remote sensor but typically
include positioning, tracking and safety and security related
controls. The current configuration of the remote sensor and
asset combination is part of the information stored into the
database dedicated to assets. This database is queried by the
Web Client to determine which command functions, if any, to
show to a user when a certain asset is selected. In addition to
asset information that can be queried using the Web Client,
spatial information regarding the current address of assets or
nearby streets can also be queried using the geo-referencing
tools available in the Web Client. The nearest vector feature to
a mousé click is determined using a nearest vector feature
search algorithm. Each vector feature has metadata that
includes the necessary identification numbers that allow the
Parent Shell to request extended information regarding the
feature.
While the Web Client can run on numerous platforms, there are
certain requirements that must be met in order for a computer to
properly run the Web Client. The primary requirement is that
the client computer must have a recent Java Virtual Machine
(JVM) available. A JVM is necessary in order to run the Java
based Web Client and to provide the built-in Java classes that
are used by the application, so that the downloaded application
can be as small as possible. The JVM is also necessary to run
other Java applications. Fortunately, JVMs are offered by
numerous providers for multiple platforms and operating
systems. The version developed by Sun is one of the most
popular and featured-filled, which is not surprising since Java
was developed by Sun. It is freely available for download from
Sun's website and is known as the Java Run-Time Environment
(JRE).
When a user first accesses the Application Module, the Web
Client is downloaded onto the user's computer, compiled and
executed within the Internet browser environment. Once the
initialization processes are complete, the Web Client is in a
blank state with no data or parameters stored in the Web
Clients memory. It must then request an
parameters from the Application Module back at the Office
server. This first set of parameters provides important details
regarding the map and data that would be needed for the rest of
the client session. It provides the access addresses for the Data
and Relay Server modules, the coordinate extent of the selected
map area as well as information regarding other map data
sources that are available from the Data Modules.
When a vector data message is received from the Data Module,
the Parent Shell passes the message to the Map component. The
contents of a vector data message includes the coordinate extent
of the new visible area, the vector feature type (polygons,
initial set of
204
polylines, etc.), metadata regarding each distinct vector
feature's class as well as any assets that are within the visible
area. The Map decodes the packed vector and asset data into an
array of coordinates, converting from coordinate space to the
display space using the coordinate extent of the visible area.
Each vector feature is drawn onto the display using Java
provided tools for drawing polygons and polylines. Information
about assets can be provided in graphical form, by indicating
the location of assets on the map, or in text and tabular form
using JSPs to query the Data Module's database for current or
historical information.
A unique ability offered by the Platform is the ability for users
to remotely check on and control assets in real-time. This is
possible through the integration of the Aeris MicroBurst service
with CSI Asset-Link sensors. Users can issue a specific
command through the Web Client to the. Communication
module. It passes the message onto the Aeris's AS server. Aeris
then proceeds to deliver the command by paging the onboard
Asset-Link sensor which then performs the desired operation
and reports back the success or failure of the operation as well
as any results that may have occur. An Asset-Link sensor can
be preprogrammed to perform a series of operations
automatically based on conditions or triggered manually
through a page. Operations of use in real-world applications
include requests for current positions, unlocking doors, arming
and unarming alarm systems, enabling or disabling engine
ignition, speed limiters and continuous tracking. The configured
operation and their numbered command strings are stored into
the sensor database as the configuration can be unique for
different sensors and/or asset combinations. For security
reasons, the actual command strings and sensor identification
numbers are not shown to users.
4. TESTING RESULTS
A prototype system, named as iVCAMS3 (Internet-based
Vehicle Control And Monitoring System for Safety and
Sccurity), has been developed using the development platform
at The University of Calgary to monitor and control vehicles for
safety and security purposes. The main screen can be seen in
the following figure.
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Figure 1. iVCAMS3 main screen
4.1 Field Testing
Field-testing was conducted to ensure that iVCAMS3 could
successfully receive messages from Asset-Link equipped assets
using the MicroBurst network and send commands back. Asset-
Link sensors were placed onto cars in several cities throughout
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