How Does a GPS Ankle Bracelet Work?

By Kevin Rail


The acronym "GPS" stands for global positioning system, which is based on a satellite signal. There is a type of GPS that is used in the criminal justice field. It is in the form of an ankle bracelet that gets attached to an offender to track his whereabouts in a designated area. Ankle bracelets are usually used with pre-trial offenders who are out on bond and waiting for their final case. They also are used to monitor people who are out on parole. They are used to cut down on prison populations.


One type of GPS ankle bracelet is called an active unit. When an offender wears this type of bracelet, she has little chance of getting far from acceptable areas because the data is collected is in almost real time. It is bounced down to a secure website from the satellite, and officers can get the location of the offender almost immediately.


A passive GPS unit works a little bit differently. In this case, the offender's data is stored throughout his daily activities. He then comes home and places the unit in a docking station. This is also called a charging station. It gets plugged into a power outlet and the offender's home phone line. The officers then evaluate the data through the secure website to see where the defendant was through the course of the day.

Data Collection

The data that is being collected is based on of a few different variables. In both types of units, locations on a map are plotted out. The data is then based on of these points. The offender's direction, traveling speed, time of day and date are all monitored.


Another feature of the ankle bracelet is that it tracks various zones that an offender is allowed to travel. Inclusion zones are allowed and exclusion zones are not. Exclusion zones include areas where a victim might work, live or spend a lot of time. If an offender happens to enter an exclusion zone, the officers notify the victim that she is there or they actually go right to the location if necessary.

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