08-16-2017, 09:16 PM
[attachment=7415]This article is presented by:
SAJEEV R
S7 IT
SOE CUSAT
2007-2011
Automatic Vehicle Locator
1. INTRODUCTION
Is your car or vehicle stolen or not visible in the thickest snow or is one among several cars present? Do you want to know the arrival of bus for which you are waiting.are your children going alone in a vehicle and you want to track their moments? Does your cargo consist of costly load and you want to protect them?do you want to keep track of your little playing kids about where they are? The answer is 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 fea-tures in conjunction with AVL system implementation. Simple AVL systems include: computer -aided dispatch software, mobile data terminals, emergency alarms, and digital communications. More sophisticated AVL Systems may integrate: real-time passenger information, automatic pas-senger 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 ser-vices.
2. WHAT IS AVL TECHNOLOGY?
Automated Vehicle Locaton (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 com-pensate for inevitable shortcomings of any one technology. The four principal technologies em-ployed for AVL systems are:
1.Global Positioning System
The Global Positioning System (GPS) is a space-based global navigation satellite system that provides reliable location and time information in all weather and at all times and anywhere on or near the Earth when and where there is an unobstructed line of sight to four or more GPS sa-tellites. It is maintained by the United States government and is freely accessible by anyone with a GPS receiver.
GPS was created and realized by the U.S. Department of Defense (DOD) and was originally run with 24 satellites. It was established in 1973 to overcome the limitations of previous navigation systems.
GPS consists of three parts: the space segment, the control segment, and the user segment. The U.S. Air Force develops, maintains, and operates the space and control segments. GPS satellites broadcast signals from space, which each GPS receiver uses to calculate its three-dimensional location (latitude, longitude, and altitude) plus the current time.
The 24 satellites that make up the GPS space segment are orbiting the earth about 12,000 miles above us. They are constantly moving, making two complete orbits in less than 24 hours. These satellites are travelling at speeds of roughly 7,000 miles an hour.
The Global Positioning System (GPS) is a satellite-based navigation system made up of a net-work of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was originally intended for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS.
2. Dead-Reckoning System
Dead reckoning (DR) is the process of estimating one's current position based upon a previous-ly determined position, or fix, and advancing that position based upon known or estimated speeds over elapsed time, and course. While traditional methods of dead reckoning are no longer considered primary means of navigation, modern inertial navigation systems, which also depend upon dead reckoning, are very widely used.
A disadvantage of dead reckoning is that since new positions are calculated solely from previous positions, the errors of the process are cumulative, so the error in the position fix grows with time.
An inertial navigation system (INS) is a navigation aid that uses a computer, motion sensors (accelerometers) and rotation sensors (gyroscopes) to continuously calculate via dead reckoning the position, orientation, and velocity (direction and speed of movement) of a moving object without the need for external references. It is used on vehicles such as ships, aircraft, submarines, guided missiles, and spacecraft. Other terms used to refer to inertial navigation systems or closely related devices include inertial guidance system, inertial reference platform, inertial instrument, and many other variations.An inertial navigation system includes at least a computer and a platform or module containing accelerometers, gyroscopes, or other motion-sensing devices. The INS is initially provided with its position and velocity from another source (a human operator, a GPS satellite receiver, etc.), and thereafter computes its own updated position and velocity by integrating information received from the motion sensors. The advantage of an INS is that it re-quires no external references in order to determine its position, orientation, or velocity once it has been initialized.
Signpost/Odometer Systems
An odometer (mileometer, milometer) indicates distance travelled by a car or other vehicle. The device may be electronic, mechanical, or a combination of the two.
Recently, exercise enthusiasts have observed that an advanced Global Positioning Satellite (GPS) receiver (GPS) with an odometer mode serves as a very accurate pedometer for outdoor activi-ties. While not truly counting steps (no pendulum is involved) an advanced GPS odometer can reveal the accurate distance traveled to within 1/100th of a mile (depending on the model, per-haps 1/1000th of a mile). 1/1000th of a mile is approximately the distance of a single pace or 2 steps (1.609 m). Precise metric odometers have a precision of 1/100 or 1/1000 km, 10 or 1 me-tre(s) respectively.
A GPS with odometer mode is also an excellent and inexpensive means to verify proper opera-tion of both the speedometer and odometer mounted in a vehicle.
To track and locate vehicles along fixed routes, a technology called Signpost transmitters is employed. This is used on transit routes and rail lines where the vehicles to be tracked continually operated on the same linear route. A transponder or RFID chip along the vehicle route would be polled as the train or bus traverses its route. As each transponder was passed, the moving vehicle would query and receive an ack, or handshake, from the signpost transmitter. A transmitter on the mobile would report passing the signpost to a system controller. This allows supervision, a call center, or a dispatch center to monitor the progress of the vehicle and assess whether or not the vehicle was on schedule. These systems are an alternative inside tunnels or other conveyances where GPS signals are blocked by terrain.
4. Radio Navigation/Location
Radio navigation is the application of radio frequencies to determine a position on the Earth. It uses signals broadcast from special radio stations. Electronic equipment on the plane uses these signals to indicate the location and direction of the plane with respect to the transmitting station. Radio navigation is used by almost all pilots Radiolocating is the process of finding the location of something through the use of radio waves. It generally refers to passive uses, particularly radar as well as detecting buried cables, water mains, and other public utilities. It is similar to ra-dionavigation, but radiolocation usually refers to passively finding a distant object rather than actively one's own position. Both are types of radiodetermination. Radiolocation is also used in Real Time Locating Systems (RTLS) for tracking valuable assets.
3. TRACKING SYSTEMS
There are two types of tracking systems.
Several types of Vehicle Tracking devices exist. Typically they are classified as "Passive" and "Active".
"Passive" devices store GPS location, speed, heading and sometimes a trigger event such as key on/off, door open/closed. Once the vehicle returns to a predetermined point, the device is re-moved and the data downloaded to a computer for evaluation. Passive systems include auto download type that transfer data via wireless download.
"Active" devices also collect the same information but usually transmit the data in real-time via cellular or satellite networks to a computer or data center for evaluation.
Many modern vehicle tracking devices combine both active and passive tracking abilities: when cellular network is available and a tracking device is connected it transmits data to a server; when network is not available the device stores data in internal memory and will transmit stored data to the server later when the network becomes available again.
There is a popular misperception that GPS is a "tracking" technology and therefore that it can be easily misused by public agencies and private companies to monitor people's whereabouts.
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.
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 dis-patch. 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. SOFTWARE
Automatic vehicle location (AVL) is a system that enables companies to trace and coordinate the movements of their fleet of vehicles. Much of the AVL software has been created for fleet man-agement and vehicle location purposes. The AVL communications software system was built based on the geographic information system (GIS) environment, but these types of systems use short message service (SMS) technology
This system is based on a known technique in computer algorithms called greedy technique (GT). The main task of the proposed software is to compute the optimal path between two real GIS coordinates. The shortest path algorithm Dijkstra s algorithm (GA) and made it compute the optimal path but not the shortest.
This depends on the proposed cost function (CF); it considers many parameters such as travel time, street condition, topography, average speed, distance and number of traffic lights. The second task is to find the minimum spanning tree (MST) based on Kruskal s algorithm (KA) on GIS digital maps with the proposed CF as graph weight. The third task is to apply the Geofenc-ing technique based on global positioning system (GPS) readings. A buffer zone area as a rec-tangle was made to compute the borders of this fencing as real coordinates, and if the fleet steps out of the border the system will raise an alarm.