AVL – Automatic Vehicle Locate

5 Nov 2010

GPS – Global Positioning System is a system of 24 satellites orbiting the earth.

GPS is the shortened form of NAVSTAR GPS. This is an acronym for NAVigation System with Time And Ranging Global Positioning System. GPS is a satellite-based system that uses a constellation of 24 satellites to give a user an accurate position. Depending on the type of GPS receiver used and the technique employed, positions can be reported within 15m to 1cm or less.  Each GPS satellite has several very accurate atomic clocks on board. Each satellite continuously transmits a signal with the exact time and satellite identification. Using this data, any GPS receiver on earth can calculate it’s position on earth and express it in latitude, longitude and altitude at a known time. By comparing two sets of that data, a GPS receiver can also determine the speed and direction the receiver is traveling over a measured period of time.

GPS was originally designed for military use. However, anyone with a receiver and the technology to use it were free to do so. It was quickly adopted into civilian use, initially with accuracy restricted by the U.S. Government for military reasons. Two of the first major civilian applications to emerge were marine navigation and surveying. In May 2000 the “signal degradation” by the government was turned off and all now have access to the native accuracy of the GPS system. As GPS receiver, antenna, and installation costs have come down and accuracy costs less, many other applications have followed.

Telematics – the integration of wireless communications, vehicle monitoring systems and location devices. In a simple form, telemetry refers to the collection or monitoring of various sensor data contained in a vehicle, such as a school bus door position sensor. In this example, along with the GPS co-ordinates, and time of day, an event could be triggered each time the bus door opened and closed and the data would be transmitted. This data could then be integrated into a database and application system to assist a bus operations management team to improve bus operations. Other examples of telemetry include interfacing a unit to the on-board vehicle computer data bus.

This could allow the transmission of engine fault codes to the vehicle maintenance function – fostering dramatic improvements in vehicle performance enhancements and a reduction in fleet maintenance costs. Other event data such as engine temperature or oil pressure variations can be monitored also providing the same benefits. In today’s vehicles there are over two hundred various data elements available from the standard data interface bus in vehicles. There are also control features available such as opening and closing door locks, modifying emissions system settings for optimal operations among many other active functions that can be remotely controlled.

Typically, there is a separate “black-box” interface unit that connects to both the vehicle data bus, and to the GPS/AVL communications unit, (also commonly referred to as a “black-box” rather than combined functionality.

It is of key importance that it is through Telemetry data gathering, processing and exception reporting that fleet owners would be able to automate the monitoring of driver performance. While standard GPS data types of Lat/Lon, speed, direction and time, provide for when a bus is at a certain location and speed it is by coupling this information with event data that a system begins to deliver to its potential.

The resultant dilution of performance monitoring could be dramatically improved via Telemetry data management. A simple example of this would be to monitor the usage of turn signals by the driver when at intersections, or does the driver come to a full stop and open/close the door at appropriate times. Other safety related functions such as open/closing of emergency doors could be monitored. These can be done both in a driver vehicle daily check and during normal operation of the truck/bus. Sometimes it is necessary for the emergency door to be opened and sometimes it’s a major safety violation. Telemetry data brings this dimension to improving fleet operations management.

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