29-01-2010, 07:50 AM
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AUTOMATIC VEHICLE LOCATOR
Abstract
Is your car or a vehicle stolen or is it not visible in the thickest
snow or is one among the several cars present? Do you wa nt to know
the
arrival of the bus for which you are waiting? Are your children going
alone in a vehicle and you want to track their moments? Does your
cargo
consists of costly load and want to protect them? Do you want to keep
track of your little playing kids about where they are?
ANS: Automatic Vehicle Locator. This Paper gives us a novel approach
of
using certain GPS technology in tracking not only vehicles, but even
children and to protect precious goods. So this technology has gained
a
lot of importance in the recent years. This paper tells us how this
technology works, its applications. It is still under research and
development stage.
1. AUTOMATIC VEHICLE LOCATOR Automatic vehicle location (AVL) is a
computer -based vehicle tracking system. For transit, the actual real
-time position of each vehicle is determined and relayed to a control
center. Actual position determination and relay techniques vary,
depending on the needs of the transit system and the technologies
employed. Transit agencies often incorporate other advanced system
features in conjunction with AVL system implementation. Simple AVL
systems include: computer -aided dispatch software, mobile data
terminals, emergency alarms, and digital communications. More sophist
icated AVL Systems may integrate: real-time passenger information,
automatic passenger counters, and automated fare payment systems.
Other
components that may be integrated with AVL systems include automatic
stop annunciation, automated destination signs, Vehicle component
monitoring, and Traffic signal priority. AVL technology allows
improved
schedule adherence and timed transfers, more accessible passenger
information, increased availability of data for transit management
and
planning, efficiency/productivity improvements in transit services .
2. What is AVL technology? Automated Vehicle Locator (AVL) systems
use
satellite and land communications to display each vehicle's location,
status, heading, and speed on the computer's screen. AVL systems use
one of four types of navigation technology, or may combine two of
these
technologies to compensate for inevitable shortcomings of any one
technology. The four principal technologies employed for AVL systems
are: 1. Global Positioning System
2. Dead-Reckoning System
3. Signpost/Odometer Systems 4. Radio Navigation/Location
3. TRACKING SYSTEMS There are two types of tracking systems. 3.1.
PASSIVE TRACKING: The Passive Tracking System modality refers to
stand
-alone GPS Receivers, which store data for further process. Passive
systems are typically limited to vehicle tracking only. When a
Passive
Tracking Device is installed in a vehicle, the location, time,
velocity
and heading data is usually stored in the unit or transferred to a
handheld device and downloaded from the vehicle when the vehicle
returns to their base station. 3.2. REAL TIME TRACKING Real Time
Tracking Systems are based on mobile stand-alone terminals which
combine GPS and GSM technology to determinate and transmit their
position. A two-way wireless communication page link connects the unit
with
the control center at all times. A portable GPS tracking device can
be
used as an emergency cellular phone with speed dialing for two -way
voice communication. It can silently call any emergency number in the
world for immediate assistance. The emergency silent call feature
also
provides a digitized voice message which can report the time, date,
speed, heading, and location of a person in distress. Figure1. GPS
Receiver The AVL tracking system consists of a GPS receiver inside
the
vehicle and a communications page link betwee n the vehicle and the
control
Center as well as pc -based tracking software for dispatch. The
communication system is usually a cellular network similar to the one
used by cellular phone. Currently all kind of communications networks
permit Real-Time Tracking for mobile assets.
4. WORKING OF A GPS BASED AUTOMATIC VEHICLE LOCATOR 4.1. GPS
SATELLITES
The GPS satellites locate the transit vehicles by sending out GPS
signals to be picked up by vehicles GPS UNITS. The GPS unit in the
vehicle absorbs the signals and gives radio signals to the RADIO
system. Figure2. A GPS Based AVL System 4.2. RADIO SYSTEM The RADIO
systems receive the vehicle GEO - LOCATION coordinates and transmits
th
is radio signals to communication center.
4.3. COMMUNICATION CENTER The communication center receives this
information and uses it to determine the location of transit vehicle
and sends this to dispatch stations and other stations for further
analysis of the information either through wire line or wireless
networks.
4.4. DISPATCH SECTION The dispatch section uses the vehicle
information
to help maintain transit schedules and provide operational support to
the drivers.
4.5. CUSTOMER ASSISTANCE UNIT The customer assistance
planning/scheduling operations analysis unit also receives the
vehicle
location information through wire line or wireless network. This
section use vehicle location map to help maintain transit schedules
to
analyze and provide traffic information for other road way driver.
Figure3. Working of a GPS based AVL
5. INTEGRATING AVL WITH OTHER SYSTEMS Buses equipped with AVL offer
many possibilities for transit interface with highway and traffic
organizations or transportation management centers. Opportunities
include: providing transit buses with traffic signal priority;
obtaining traffic congestion data at the dispatch center to allow
rerouting of buses or informing customers of delay; incorporating
transit information in traveler information systems; developing multi
-application electronic payment systems; using buses to automatically
communicat e traffic speed; and reporting of roadway incidents by
transit vehicle operators. 6. MORE ABOUT GPS
6.1. Use of Differential GPS For AVL systems which do require more
accurate positions, differential GPS can be employed. These systems
normally employ the transmission of correction information to the GPS
receiver; this correction information has corrections for each
satellite in view. This is done because each satellite has its own
error; the error in GPS is not simply an X-Y error which will be the
same for all receivers. The error on any two given receivers will
only
be the same if those receivers are using the SAME satellites. This
canâ„¢t normally be guaranteed as satellites may be obscured at one
location, making the error slightly different for two receivers. 6.2.
GPS Antennas The best position for any antenna is generally as high
as
possible with the best unrestricted view. 6.3. GPS Satellites The
global positioning system (GPS) was specifically engineered so that
at
least four of the 24 sat ellites would be positioned on the horizon
at
all times. There are six different orbiting patterns that the GPS
satellites follow, making a complete trip around the earth every 12
hours. The information regarding the location of the transit vehicle
is
calculated by TRILATERATION method. With this information, the
receivers can, by a process similar to triangulation, tell the user
the
exact location in latitude, longitude, and sometimes altitude too .
Figure4. GPS Satellites
6.4. MAPPING At any control station, data is normally required to be
viewed on a map. Maps allow a tangible, understandable view of a
vehicles location, and will also allow operators to apply local
knowledge.
7. DATA TRANSFER The two most common methods of transmitting vehicle
location data to dispatch are through polling and exception reporting
via wireless communications. Many agencies use a combination.
8. BENEFITS The most extensive and rigorous research into the
benefits
of AVL has found that this technology has lead t o significant
transit
firm productivity gains (whether output is measured by Passenger
Miles
or Vehicle Revenue Miles). Benefits have been documented to varying
degrees for all of the following categories.
8.1. Operations: Increases transit rider ship. Reduced need for
additional road supervisors and manual data entry. 8.2.
Communications:
Improved communications between supervisors, dispatchers, and
operators
and reduced voice radio traffic. 8.3. Passenger Information: Provides
capability to inform passengers of predicted bus arrival times thus
enhancing the quality of transit service and allowing travelers to
make
better travel decisions. 8.4. Scheduling and Planning: Provides more
complete and accurate data for scheduling and planning. Aids in
effective bus stop placement (when combined with a G.I.S. database
and
automatic passenger counters). 8.5. Safety and Security: Enhances the
security of the driver and traveler (particularly when coupled with
silent alarm technology). 9. USES 1. Vehicle location display in
real-
time. 2. Recording of arrival and departure times (proof of delivery
etc). 3. Monitoring of driving practices (speed). 4. Alerts if
vehicle
leaves or enters a defined area . 10. APPLICATIONS IN OTHER FIELDS
10.1. In Military It is clear how useful this technology would be for
the Armed Forces. Before small GPS receivers were available, troops
in
the field depended on the same technology for generations: the
compass,
sextant, maps and hand calculations. Radios and reconnaissance
aircraft
wer e great leaps, but a GPS calculates position in real time, down
to
three foot accuracy! 10.2. Geo-Caching This is for people who have
liking towards searching hidden things or participating in scavenger
hunts. With GPS, comes the new twist: geo-caching. Geo-catchers hide
a
little treasure in a box public place, for example, a shoe box with a
used book inside, taped under the seat of a bus stop. They then go to
geo-caching websites and post simple latitude and longitude, to as
much
accuracy as they like. Then other geo-catchers search for these boxes
with their GPS data. The fun is looking for a strange box in what
could
be an area with a 25 -foot radius. When the successful geo-catcher
finds the box, he or she keeps the little treasure and replaces it
with
another, for the next searcher. 10.3. Track Anything Parents always
worry about their teenage kids, especially after they start driving.
Auto shops have started offering installation of small, hidden GPS
receivers in kidsâ„¢ cars. Parents can then use simple computer
software
and have their kidsâ„¢ movements plotted on a map. Many parents donâ„¢t
even tell the kids about this Ëœlittle extraâ„¢. Figure5. Track anything
10.4. In Cargo Some containers of cargo are more valuable than
others.
A small GPS receiver inside the cargo can know exactly where it is,
how
far it is from the destination, and where to find even it if it is
stolen. Figure6. GPS in Cargo 10.5. Child Tracking Of topical
interest
at this time is Ëœchild trackingâ„¢, giving the possibility for children
to wear or carry some sort of GPS/GSM tracker. Such a device could
provide valuable information if a child is abducted or lost. Signals
could be sent from the tracker every few minutes to a central site so
that a record is kept of the childâ„¢s loca tion, or just sent when a
Ëœpanic buttonâ„¢ was pressed by the child. 12. BIBLIOGRAPHY
1.calccit.org.itsdecision/serv_and_te ch/Automatic_v
ehicle_location/automatic_vehicle_location_summary.html
2.http://gpsworldgpsworld/article/articleDetail.j sp?
id=102387
