Implementinga

Vehicle Fleet Tracking Systemwith GPS

Author: Steven Potter© Spottek Systems 2007

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 basedVehicle Fleet Tracking System?

• Each vehicle in the fleet needs to be able to determine and report its positionGPS receiverNetwork Digital Radio

• Network base station collects and records vehicle position reportsVehicle IdentificationDate and timePosition data/coordinatesDatabase

• Vehicle Information Database to manage information for vehicle fleetIn addition to data collected from vehicle radio network - could include

Driver identificationDriver or vehicle, or both, scheduling dataVehicle maintenance schedules, logs

• Mapping applicationQuery database for vehicle position dataPlot 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 aVehicle 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” http://interactive.linuxjournal.com/article/7467 Linux Journal

2. “The Global Positioning System: The Role of Atomic Clocks” http://www.beyonddiscovery.org/content/view.page.asp?I=1275

Beyond Discovery

3. How [GPS] works http://www.trimble.com/gps/howgps-triangulating.shtml Trimble

4. GPS: the Mathematics and the Technology http://mail.colonial.net/~abeckwith/gps.html

Anthony Beckwith: Advanced topics in Mathematics

© Spottek Systems 2007