GPS was Developed by the U.S. Department of Defense for the military, the Global Positioning System (GPS) is a worldwide, satellite-based, radio navigation system that will give you the exact position of your vehicles, no matter where they are, what time it is, or what the weather is like. A total of 24 satellites orbit the Earth, monitored continuously by earth stations. The satellites transmit signals that can be detected by GPS receivers located in your vehicles and used to determine their location with great accuracy.

Working of GPS:

v Each GPS satellite transmits radio signals that enable the GPS receivers to calculate where its (or your vehicles) location on the Earth and convert the calculations into geodetic latitude, longitude and velocity. A receiver needs signals from atleast three GPS satellites to pinpoint your vehicle’s position.

v GPS Receivers commonly used in most Vehicle tracking systems can only receive data from GPS Satellites. They cannot communicate back with GPS orany other satellite.

v A system based on GPS can only calculate its location but cannot send it to central control room. In order to do this they normally use GSM-GPRS Cellular networks connectivity using additional GSM modem/module.

Important aspects of GPS:

v GPS Receiver can only Receive data and cannot send data to Satellite

v GPS satellites do not know the position of a GPS Receiver. GPS Receiver calculate its position using data from 3-4 satellites and no single satellite know the calculations done by GPS receiver or its position.

v GPS satellites do not know the position of a GPS Receiver. GPS Receiver calculate its position using data from 3-4 satellites and no single satellite know the calculations done by GPS receiver or its position.

v GPS satellites are different satellites and can only send small and week radio signals to earth.

v GPS Satellite signals are weak and can be received normally with GPS antenna (external or integrated with GPS receiver) facing open sky. GPS signals cannot be received inside the home, building, garage, bridges. Even clouds and Trees can prevent GPS signals from reaching GPS receiver. Hence no GPS receiver can guarantee performance. Certain advanced and sensitive GPS receivers can receive signals in above situations but performance is still not satisfactory.

v GPS receivers have cannot give accurate position, Normally errors from plus/minus 5meters to 25 meters are possible.

v GPS receiver only give Latitude, Longitude and Velocity calculated. To know your location you need highly accurate map. If maps are not accurate you will have much high error in location. Normally accuracy of Maps is considered more important then accuracy of GPS Receiver.

Simple GPS Products:

GPS Mouse/Receiver for Laptop/computer

GPS Compact Flash card for PDAs

GPS Bluetooth Receiver for PDA’s , Mobile Phones

GSM:

v GSM, Global system of Mobile, is a popular Mobile communication system provided by Cellular service providers or GSM Operators in most countries internationally.

v It is used for in most mobile handsets used by us.

v GSM Mobile communication system can be intelligently used by electronic devices which can collect some data and send it to the central place using SMS or GSM data call.

v GSM is required in Vehicle tracking systems because GPS system can normally only receive location information from satellites but cannot communicate back with them. Hence we need some other communication system like GSM to send this location information to central control room.

v Other technologies can also be used but they are more costly.