Abstract
AVL systems mainly contains road side fixed station and moving nodes. It uses technology named as ITS (intelligent transport systems).Mostly transport systems used GPS (global positioning system).By using GPS technology, a satellite transmission. It uses the time, signal sent form the sender and from the receiver .To calculate the location we used time difference .It used DGPS receivers .This system is low coast and affective product. This system ensures safety too .Vehiclelane-Determining that connects to a wireless communication systems contain onboard differential GPS receiver channel, a digital roadway database and algorithm also.
Index Terms: GPS (global position system), DGPS, ITS, Roadway database.
Literature Review
History of GPS is not so old. GPS technology known as new technology because, advancement level increases, hardware level and other mechanism become solid and better implementation of AVL. And AVL used mostly GPS, GIS etc. First
AVL installed at Chicago Transit Authority in 1968. At that time they used signpost technology. AVL we can say sub system of ITS (intelligent transport system).
Introduction
AVL (automated vehicle system) is most renowned technology in transportation systems. GPS is a global term its heart is GPS satellites. It locate the position of anything that you want to track. It used the principle of calculation of demodulation of radio signals. As we know every satellite has its own wave form (identification wave length/ID).
Many systems and networks used GPS to find position or communication purpose. The nodes i.e.; vehicles and roadside stations are Dedicated Short Range Communications (DSRC) devices. DSRC works in 5.9GHz band with bandwidth of 75 MHz and approximate range of 1000m.
Another beneficial use of GPS is TRACKING. This paper deals use of GPS. Actually GPS used to navigate the air traffic, ground Traffic and we can say mostly used to tracking. In this we discuss about its uses, applications, hardware, roadside stations, and implementation of GPS receivers.
GPS
First of all we need to understand what GPS (global positioning system) is.
GPS is a navigation system based on satellite it is made by U.S defense department. GPS is originally made for defensive use in military, In 1980s U.S government made this system available for the public use. GPS worked 24 hours in the whole world in any condition of weather.
There is no fees charges for the use of GPS it is free of cost.
GPS system made of a 24 satellite network that is placed in orbit.
First GPS satellite launched in 1978 Full 24 satellite achieved in 1994 GPS satellite having a 2,000 pound weight and 17’ across with solar panel
GPS transmitter’s power is 50 watt 0r less than 50 watts.
In this fig.we can see, and easily understand the reality and working of GPS. In GPS system Satellites are used, they calculate the time and signals that are transmitted. It shows the location of the vehicle at anywhere on earth.
Dedicated Short-range Communications
DSRC, in transportation system most common component. Dedicate short-range communication refers to communication between vehicle to vehicle, fixed station/node to vehicle. It is known as shortrange or wireless communication. Its concern is safety mainly.
Now we talk about the working of AVL systems. The satellite send some waves of different wave-lengths. Receivers received that waves but this process known as Triangulation. It is a process in which determination location of a point by recording the angles.
A GPS receiver is installed in the car. GPS system will transfer and receive desire information from the nearest GPS satellite. When the position of vehicle has calculated, then GPS receiver transform its location to control center server using the cellular network. Now the current position of
Vehicle can see by the registered user.
Satellite
Satellite is artificial object placed into an orbit. Such artificial objects are called artificial satellite. Satellite is a planet, moon or machine that’s orbit are star or planet. e.g. earth is satellite and its orbit is sun.
Importance
Improved efficiency of the system. The monitoring capability of the AVL system allows the agency to make better decision about scheduling and routing. Routes that show poor patronage can be rescheduled to demand-response or flex route. · Improved customer communication. Disputes about non-arrival of vehicles and similar customer complaints can be better handled because documented evidence of the real-time location of vehicles is available from the AVL system. · Better flex routing services. The AVL technology allows the flexibility of incorporating some demand-responsive services such as route deviation into the regular fixed-route service.
This is particularly important for small agencies and para-transit services that operate in a low-density environment. Agencies like Woodbridge, VT (PRTC) that operate in low density areas could encourage choice riders by offering flex route services and convenient pick-up points. It is very useful for para transit services where the vehicles can be guided to the correct address.
Decreased reservation time. Para-transit services usually required 24 to 48 hour advance reservations prior to the AVL system. With the AVL the reservation time has been brought down to one or half an hour in many cases. Occasionally real-time scheduling can also be done, which a great time is saving to passengers. · Efficient use of resources. Most small and medium sized agencies are operating on tight budgets and cannot generate enough revenue to improve the services. They felt that an AVL system would help utilize the resources more efficiently by improving the vehicle miles traveled (VMT) by introducing demand responsive services in regular fixed routes (COLTS, 1997).
Monitor and improve on-time performance through fleet tracking. The GPS output helps identify trouble areas and can be used to improve on-time performance. · AVL permits automated dispatch and scheduling (Nelson 1995; Khattak et al 1998; Tellechea and Stone 1998). · AVL enhances the ability to do automated billing and payroll.
Written by: Sarmad Tariq
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