The consumer electronics market was quick to offer remedies (radar detectors) to radar guns; a similar market may exist for devices to counter satellite tracking devices. Radio jamming of the relevant GPS or cell phone frequencies would be an option, as would a device which could detect the RF emissions of the GPS receiver circuitry. Though jamming of GPS signals could create a safety hazard to vehicles or aircraft within line of sight of the jammer and any deliberate radio interference is likely to be illegal in most western countries.

Besides this, jamming the transmission frequency of an industrial grade GPS transmitter would only work temporarily because most of them use a “store and forward” procedure to store up points that were not received and transmit them again later. This capability is built-in so tracked vehicles don’t lose data when they are out of cellular range temporarily. Jamming the actual GPS frequency, however, would result in the GPS transmitter simply thinking it had lost sight of the satellites.


In the US, the use of GPS trackers by police requires a search warrant, but use by a private citizen does not, as the Fourth Amendment does not limit the actions of private citizens. These devices can also raise concerns about personal privacy. Over time, the information collected could reveal a typical pattern of movements.


Data pullers

11Jun07

Contrary to a data pusher, that sends the position of the device at regular intervals (push technology), these devices are always-on and can be queried as often as required (pull technology). This technology is not in widespread use, but an example of this kind of device is a computer connected to the Internet and running gpsd.


Data pushers

11Jun07

This is the kind of devices used by the security industry, which pushes (i.e. “sends”) the position of the device, at regular intervals, to a determined server, that can instantly analyze the data.

These devices started to become popular and cheaper at the same time as mobile phones. The falling prices of the SMS services, and smaller sizes of phone allowed to integrate the technologies at a fair price. A GPS receiver and a mobile phone sit side-by-side in the same box, powered by the same battery. At regular intervals, the phone sends a text message via SMS, containing the data from the GPS receiver.

The applications of these kind of trackers include:

* Fleet control. For example, a delivery or taxi company may put such a tracker in every of its vehicles, thus allowing the staff to know if a vehicle is on time or late, or is doing its assigned route. The same applies for armored trucks transporting valuable goods, as it allows to pinpoint the exact site of a possible robbery.
* Stolen vehicle searching. Owners of expensive cars can put a tracker in it, and “activate” them in case of theft. “Activate” means that a command is issued to the tracker, via SMS or otherwise, and it will start acting as a fleet control device, allowing the user to know where the thieves are.
* Animal control. When put on a wildlife animal (e.g. in a collar), it allows sciencists to study its activities and migration patterns. Vaginal implant transmitters are used to mark the location where pregnant females give birth. Animal tracking collars may also be put on domestic animals, to locate them in case they get lost.
* Race control. In some sports, such as gliding, participants are required to have a tracker with them. This allows, among other applications, for race officials to know if the participants are cheating taking unexpected shortcuts or how far apart they are. This use has been featured in the movie “Rat Race”, where some millionaires see the position of the racers in a wall map.
* Espionage/surveillance. When put on a person, or on his personal vehicle, it allows the person monitoring the tracking to know his/her habits. This application is used by private investigators, and also by some parents to track their children.


Data loggers

11Jun07

A GPS logger simply logs the position of the device at regular intervals in its internal memory. Modern GPS loggers have either a memory card slot, or internal flash memory and a USB port to act as a USB flash drive. This allows easy downloading of the data for further analysis in a computer.

These kind of devices are most suited for use by sport enthusiasts: They carry it while practising an outdoors sport, e.g. jogging or backpacking. When they return home, they download the data to a computer, to calculate the length and duration of the trip, or to overimpose their paths over a map with the aid of GIS software. GPS devices are also integral tools in geocaching.

In the sport of gliding, competitors are sent to fly over closed circuit tasks of hundreds of kilometres. GPS loggers are used to prove that the competitors completed the task and stayed away from controlled airspace. The data stored over many hours in the loggers is downloaded after the flight is completed and is analysed by computing the start and finish times so determining the fastest competitors.


GPS tracking

11Jun07

A GPS tracking unit is a device that uses the Global Positioning System to determine the precise location of a vehicle, person, or other asset to which it is attached and to record the position of the asset at regular intervals. The recorded location data can be stored within the tracking unit, or it may be transmitted to a central location data base, or internet-connected computer, using a cellular (GPRS), radio, or satellite modem embedded in the unit. This allows the asset’s location to be displayed against a map backdrop either in real-time or when analysing the track later, using customized software.


GPS drawing

11Jun07

GPS Drawing combines art, travelling (walking, flying and driving) and technology and is a method of drawing that uses GPS to create large-scale artwork.