Sea turtle with tracking device
Law enforcement officials, parents, pet owners, biologists, shipping companies and car owners may all use tracking devices to determine the whereabouts of people, animals or things. A tracking device is a two-part electronic apparatus; one part sends out a signal that is received by the other part. In many cases, the Global Positioning Satellite (GPS) system is incorporated into the tracking activity.
Non-GPS Devices
The transmitter of a tracking system, whether it uses GPS or not, sends out an electronic signal, or radio wave, that is picked up by the receiver tuned to the same frequency. According to the Human Interface Technology Lab in Seattle, scientists and developers employ tracking systems that do not use GPS in robotics and virtual reality systems. Instead, they use optical, electromagnetic and audio signals instead of radio waves. In any case, the same concept of trilateration is used.
GPS Devices
Systems that use GPS include surveillance devices and vehicle tracking as theft deterrents or business fleet tracking. According to NASA, the GPS system consists of 29 satellites in precise orbits around the earth. Twenty-four satellites comprise the operational constellation needed to provide GPS functionality, and there are 5 spares in case of malfunction. The orbits are set up so that there are at least 4 satellites in view from the earth at any given point at any given time.
A receiver in a car, for example, picks up signals from at least 3 satellites and calculates the distance from them by comparing the time stamps of when the signals left the satellites to the time they were received in the car. Using the results of these calculations, it then uses a process called trilateration to determine its latitude, longitude and altitude. It is because of this process that the familiar navigation systems in cars are able to display map locations to the driver.
Real-Time Tracking
A tracking device then takes the trilateration information and relays it with its transmitter to the receiver where the observer can determine the location and speed of the transmitter as it is moving. This is called "real time" tracking. People using real-time systems can see the results on the Internet or on handheld devices immediately.
Data Logging
Tracking devices that are not "real time" are called data logging. This means that the information transmitted from the tracking device, whether GPS or not, is compiled in a digital file that trackers read at a later time. A common use for this system is package delivery tracking.
Tags: tracking device, least satellites, real time