GSM Personal Tracker

The purpose of the device is to be carried by the person or vehicle
that might need to be tracked, and to provide information
about its location when interogated
by an SMS allowing the person/object to be found.

How it works

The device is fitted with a GSM sim card which links it to the GSM cellphone network in the same way as a cellphone. This enables it to receive a cellphone audio connection, an SMS and to send SMS's.

Despite its image the device does not contain any GPS location chips. It merely records the CellID number of the cell network tower that is currently communicating with the device, and sends this message back to the phone that requested the location.

The information is passed in the form of a web browser link containing the country code, service provider and unique identity number of the cell tower. By clicking on the link the web browser connects to the processing site, looks up the location of the cell tower that was used for the SMS communication, converts this to a Longitude and latitude, and shows the position of the tower on a Google Map.

Usually the tracking device will be within 500 to 1 kilometer of the cell tower.

Processing site

Details in the message are
Comverting site address
Country code (mcc)
Service provider (mnc)
Locating area code(lac)
Tower unique ID (cellid)

MCC	MNC	ISO	Country	Country Code	Network
655	21	za	South Africa	27	Cape Town Metropolitan
655	7	za	South Africa	27	Cell C
655	10	za	South Africa	27	MTN
655	6	za	South Africa	27	Sentech
655	1	za	South Africa	27	Vodacom

The processing site converts the data to a longitude/latitude format and calls up a google map link¢er=-26.179355,28.077782&size=250x250&markers=-26.179355,28.077782&zoom=14&maptype=roadmap&sensor=true

To do this conversion a database of Cell tower Ids is needed. The individual service providers do not feed their information to a central database that can be accessed by the public, and so a lot of the information is collected by volunteers. As there is no complete database, sometimes the processing program cannot find the position of a tower and as a result cannot do the conversion to longitude and latitude.

Converting a CelliD to location when the processing program fails

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