Implementing a Vehicle Fleet Tracking System with GPS Author: Steven Potter © Spottek Systems 2007Spottek Systems

Abstract This Learning Object is intended to give a very basic explanation of how the GPS system works, with a brief description of how GPS might be used, with a digital radio communications network, a database, and a mapping application, to implement a vehicle fleet tracking system. It is expected that the audience would not be directly involved in implementing such a system, but would need to know what resources might be needed to do so. (Note: This presentation will take about six minutes of your time)

What is needed to implement a GPS based Vehicle Fleet Tracking System? Each vehicle in the fleet needs to be able to determine and report its position GPS receiver Network Digital Radio Network base station collects and records vehicle position reports Vehicle Identification Date and time Position data/coordinates Database Vehicle Information Database to manage information for vehicle fleet In addition to data collected from vehicle radio network - could include Driver identification Driver or vehicle, or both, scheduling data Vehicle maintenance schedules, logs Mapping application Query database for vehicle position data Plot vehicle(s) on a map

GPS Overview The technology derived from the use of the GPS (Global Positioning System), and related systems, has made it possible to use very accurate position data, in real-time. Based on a network of 24 Earth-orbiting satellites, and dependent on atomic time- keeping devices (Ref 2), the GPS, first developed for the US military, has become a ubiquitous navigation and positioning tool. All of the GPS based, real-time, positioning systems operate by collecting very accurately time-stamped, relative, position data from a number of orbiting satellites, and computing a position in 3- dimensional space, on the Earth’s surface. {Adapted from Ref 1}

GPS: How it works At regular intervals, each satellite sends its position, in 3-dimensional space, and a time code, representing the precise time that the satellite was located at that position. A receiver can calculate its distance from each satellite position, by computing the time taken for a satellite’s signal to reach it. The receiver’s position, relative to each satellite, must be on the surface of a sphere with a radius of the computed distance, with the satellite at the sphere’s center. {Adapted from Ref 3}

GPS: How it works The relative position spheres from two satellites, will intersect in a circle. {Adapted from Ref 3}

GPS: How it works The position sphere from a third satellite will intersect the circle at two points. The position sphere from a fourth satellite will intersect one of those two points, revealing the position of the receiver. (Note: If a receiver is known to be on the Earth’s surface, which is very nearly a perfect sphere, only three satellite signals are needed to determine the receiver’s position) {Adapted from Ref 4}

Vehicle Fleet Tracking System Each vehicle in the fleet is fitted with a GPS receiver and a Network Radio Periodically, each vehicle reports its position to the Base (Control) station. (There are a variety of methods for this, depending on the type of radio network employed)

Vehicle Fleet Tracking System The Base Station collects Vehicle Identification, Date and Time, and Position data, and maintains a Vehicle Information Database

Vehicle Fleet Tracking System A mapping application can query the database for vehicle position data and plot vehicle positions onto a city street map. (Note that similar systems can be used to track trucks, planes or ships, on a larger scale)

References 1.“The GPS Toolkit” Linux Journalhttp://interactive.linuxjournal.com/article/ “The Global Positioning System: The Role of Atomic Clocks” Beyond Discoveryhttp:// 3.How [GPS] works Trimble 4.GPS: the Mathematics and the Technology Anthony Beckwith: Advanced topics in Mathematicshttp://mail.colonial.net/~abeckwith/gps.html © Spottek Systems 2007Spottek Systems