GPS World, October 2009

EXPERT ADVICE GPS Forensics Crime and Jamming By David Last T he most widely used of all GPS devices are in car navigators When vehicles carrying navigators are used for criminal purposes records contained in the devices may be examined Such investigations rely on newly developed forensic techniques that employ a combination of computer expertise and navigation knowledge yielding valuable data for crime investigators Criminals use jammers to overcome tracking systems and steal vehicles Evidence from GPS based tracking systems now fitted to a wide range of vehicles can be of even greater value These installations many of them covert provide a history of vehicle movements Forensic analysis of such records can provide evidence of considerable value in crime detection Whilst the principal purpose of vehicletracking systems is generally to provide real time information for efficient fleet control they also serve an important security function By continuously displaying up to date location information and identifying vehicles that deviate from planned routes or cross specific boundaries they help protect assets that include the vehicles themselves and their high value contents Vehicle tracking systems now constitute one of the most important GPS applications for our society The recent appearance of readily available low cost GPS jamming devices presents a real and immediate threat to all such tracking and security systems Criminals now employ jammers that can block both GPS reception and GSM in Europe and U S and other mobile phone systems throughout the world rendering vulnerable the use of GPS in critical security applications Other global satellite navigation systems GNSS in development will likely share that vulnerability While not yet deployed for criminal purposes spoofers that mimic GNSS signals will pose an even greater threat to vehicle security than jammers Alternative technologies including enhanced Loran eLoran for vehicle navigation and tracking are not vulnerable to these threats and promise a degree of protection to vehicle tracking and recovery systems These solutions will likely play an increasing role as GNSS jamming and spoofing activity increases Vehicle Navigators Vehicle navigators often contain large numbers of records created by their users These may show where they have been how they got there and a great deal more of value to investigators The destinations stored in car navigators can be extracted listed and plotted It is now possible to do this for virtually all makes and models of device whether after market installations or built in by the manufacturer Such examinations must be conducted with great care to maintain high forensic standards so the evidence will stand up in court It is also essential to preserve that evidence This requires screening receivers from incoming satellite signals during the examination this can be very difficult to achieve given the exceptionally high sensitivity of current GPS receivers Some car navigators disclose a great deal of information who owns them multiple addresses a home address plus favorite addresses destinations visited most frequently or most recently the language spoken by the user and other preferences whether the user travels abroad and occasionally telephone calls made and received Some units even contain a detailed record of journeys stretching back over months each point timed and dated see FIGURE 1 These can provide compelling evidence of criminal activity Tracking systems Probably the most impressive forensic evidence involving GPS comes from the tracking systems now fi tted to increasing numbers of trucks trailers delivery vans and rental cars Each vehicle carries a receiver that records its location and sends it at intervals to a tracking center via mobile phone data services Å FIGURE 1 Detailed tracks of routes travelled by a vehicle each point dated and timed GPS World October 2009 www gpsworld com 8