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International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B-YF. Istanbul 2004
can be timely sent to the control centre. The control centre
design is shown in Figure 2.
3 Vehicle operatin,
information daladabe
PUIS server S
Information application server Dispatch Arorkstztion
customer Maintenance man manager
Figure 2. Control centre design
The control centre stores messages in the database, which
consists of spatial, attribute and graphical data. The GIS-based
operator interface presents a digital map of the rail line and
display locations uploaded by each on-board unit onto this map.
The operator can change the area displayed and zoom in on any
particular section of the railroad line to predetermined
resolution. The locations for which alert/alarm conditions are
reported will be clearly differentiated on the map with specific
icons. The operator can see data content of any particular
message by clicking the message icon on the map. The operator
can use different queries in order to display on the interface
only the information that the operator needs, for example, the
operator can specify type of message to be displayed, vehicles
of interest, time interval, and so on. In addition to the
geographical map based display, the users have access to
various reports generated automatically from the database (Lin
et al., 2002; Derekenaris et al., 2001).
4.0 On-board Unit with GPS and Wireless Communications
The on-board unit consists of communication satellite antennae,
satellite positioning antennae, the on-board receiver system and
communication interface devices, etc (shown in Figure 3). The
on-board unit can continuously measure different parameters,
tag the data with time and position information, reports irregular
conditions.
Po
Communication satellite
GPS satellite
GSMR/ wireless cab
signal
GPS antenna
Sensors
Figure 3. On-board unit design
The on-board unit use GPS to determine its geographical
position. The signals emitted by satellite in the GPS are
analysed at the time intervals defined in advance or simply on
73
request (Chakrabarti, et al., 1999). This enables the position of
the mobile unit to be calculated. GPS signal cannot
continuously provide the positioning information when GPS
signal obstruction occurs in the tunnel or under the trees, so
auxiliary devices and techniques are needed to provide
supplemental positioning information for vehicles in above
cases. GPS, transponder and odometers will be used to position
the on-line train in the Qinghai-Tibet railway. GPS receivers
will be fabricated on a circuit board, and transform the data to
the desktop computer, thus realize real-time positioning and
display.
4.3 Communication Links between On-board Monitors and
the Control Centre
The track circuit train control system will not be available to
transmit information from trackside to on-board units in
Qinghai-Tibet line mainly due to the bad environment along the
line. There are two solutions under research. One is an
intermittent radio based on cab signal system (Wang, et al.,
2002; Ma et al., 2002). Instead of track circuit, an intermittent
radio link between the on-board units and the station is used to
transmit and receive the train control information within a
radius of 3km from the station. The control centre is connected
with the station by the optical fibre network. The other is real-
time, continuous communication between the on-board units
and the control centre. Until now, the specialists of China'
Ministry of Railways are inclined to choose the second solution.
So the paper focuses on the latter. Communication Links
between on-board monitors and the control centre of the latter
are shown in figure 4.
ü
E
[o^ s
El * GPS satellite
CLAN
Communication satellite &
me =3 ES
00000 station station I |
mmm
Wireless communication Xining control ccentre
Wire communication
Golmud maintenance centre
Figure 4. Communication link architecture
S. CONCLUSIONS
China' Ministry of Railways has produced a series of projects
and operating solutions to simplify the organisation of rail
traffic in highly mountainous areas. Even though the Golmud-
Lhasa section of the Qinghai-Tibet main line will not be
handling very substantial quantities of freight, it has been
decided that the track foundations should be built to Class I
standard for state railways. In addition, China' Ministry of
Railways will greatly improve operation management of
Qinghai-Tibet line after completion, as well as ensure the
project quality during construction. The aims of QTIMP are
oriented toward the latter. It provides the guidelines for the
information management of the Qinghai-Tibet railroad.
