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Because the use of GPS has become so widespread in our society, most people assume that if they want to track an object, GPS is how it will be done. This is not always the case. For tracking applications, GPS provides only half of the solution.
A GPS receiver uses radio signals from satellites orbiting the earth to calculate its own location. That's it. Sometimes that information is simply displayed locally on a map or recorded for future analysis, and if that is all that is needed then GPS the perfect technology for the job.
If, however, an object is being tracked remotely, sometimes referred to as Live Tracking, then the object's GPS location must somehow be sent someplace else. Remember, GPS satellites do not have two-way communication capability, as is often misunderstood, and so cannot relay any information. Most commonly, the GPS location data is sent over a cellular network via an onboard modem. This is the best choice for most applications as cellular coverage is widespread, reliable, and affordable. If, however, an object needs to be tracked where cellular coverage is not available, then another form of communication must be used. When tracking, for example, whales in the middle of the ocean or trucks that travel across vast deserts, cellular systems will not work and another technology must be employed, such as satellites. These satellites are data communication satellites, however, NOT GPS satellites and it is important to remember this distinction.
While GPS is certainly one of the greatest inventions of the 20th century, it is not always the most effective solution for remote "Live" tracking applications. Depending on the intent of the system, other technologies may need to be employed, either replacing GPS altogether, or better yet, in a supplemental role.
When a GPS receiver moves indoors or is otherwise obstructed from a view of the sky, the GPS receiver cannot "see" the GPS satellites and thus cannot calculate its precise location. The location accuracy is thus diminished. If the intent of the system is simply to report a vehicle's location as it makes deliveries around a city, such as in any fleet management system, then this is not a problem. If, however, the intent of the system is to recover a stolen vehicle or other item that may be moved indoors, then using GPS alone may not always lead to a successful recovery of the tracked object. This is why the popular LoJack System does not use GPS and instead relies solely on radio frequency (RF) tracking technology. RF tracking technology is still the only technology that can effectively and consistently track and locate an object that does not have a view of the sky.
In an RF vehicle tracking system such as LoJack, a radio transceiver, usually called a VLU (Vehicle Locator Unit), is installed in the vehicle and remains inactive until the vehicle needs to be located. When this occurs, the VLU is activated, usually by means of a remote radio activation signal that is transmitted from local radio towers. Once activated, the VLU will transmit a radio signal that can then be tracked using tracking receivers installed in police or security vehicles. The tracking receivers will pinpoint the exact location of the vehicle, even if it is hidden in a garage or cargo container.
The drawback of a system like this is that it does not provide immediate location information to the control-center and so the tracking and recovery process can potentially take a long time. The ideal solution would therefore use both GPS and RF tracking technologies and draw on the strengths of each.
The VectorTrac System from Pegasus Technologies incorporates both GPS and RF tracking technologies into one powerful solution. With the VectorTrac stolen vehicle recovery system, Pegasus puts a powerful GPS receiver onto the RF based Vehicle Locator Unit, allowing both GPS and RF tracking simultaneously. This solution provides the benefit of having an accurate initial fix via GPS combined with an RF signal which aids in the actual recovery of the vehicle.
In Pegasus' Law Enforcement Bait Bike system as well as the Stolen Property Tracking System, Pegasus combines GPS/cellular technology with two independent RF tracking transmitters to deliver the most powerful property tracking solution ever available.