Tracking TechnologiesCopyright © 2012 National Center for Justice and the Rule of Law – All Rights Reserved Page 1
NCJRL Judicial Conference April 2-3, 2012
Technology Framework
TrackingTechnologies
Don MasonAssociate Director
Copyright © 2011 National Center for Justice and the Rule of Law – All Rights Reserved
NCJRL Judicial Conference April 2-3, 2012
Digital surveillance devices?
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Digital surveillance devices?
Secure Continuous Remote Alcohol Monitor – SCRAM
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Location Tracking
• Not one, single technology
• Convergence of several technologies
• Systems for– Tracking inventory, livestock, vehicles, or
humans
– Delivering location-based services to wireless devices
NCJRL Judicial Conference April 2-3, 2012
Current Technologies• Cameras (monitoring, surveillance)• “Bumper beepers”• Two-way pagers and cellular telephones• Geographic Information Systems (GIS)• Global Positioning System (GPS)• Vehicle event data recorders (EDR)• Radio Frequency Identification (RFID)• Wireless Local Area Networks (WLAN)• 911 and Enhanced 911 (E-911)
NCJRL Judicial Conference April 2-3, 2012
• Cell phones– Networks and how they work
– Cell site location information (CSLI)
• Beepers
• Global Positioning System (GPS)
• Digital Cameras
Our Focus Today
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• Smartphones
• GPS
• Digital Cameras
• Beepers
Types of Devices
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• Game systems
• MP3 Players
• E-readers
Types of Devices
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• Cellular network triangulation
• GPS trilateration
• Geotagging
Processes
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Smartphones
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Smartphones
• Over 5.7 billion cell phones worldwide– 327 million in US
•103% of population
• 1.6 billion smartphones sold in 2010 alone
NCJRL Judicial Conference April 2-3, 2012
Mobile / Cellular phones
• Positions of mobile phones can be tracked, even on the move– Cell phones register their locations with
nearest cellular towers, approx every 7 sec’s
– Nearby antenna towers / base stations pick up signals, roam phone to adjacent towers as appropriate
– Active calls not required (most systems)
– Multilateration based on comparing multiple antenna signal strengths, pattern
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NCJRL Judicial Conference April 2-3, 2012
Cell Phone Technology
• Has become important public safety tool
• Helps find people in trouble– While GPS helps people find their way out of trouble
– Can locate lost or missing persons (or their phones)
• Even OnStar uses cellular network to communicate with GPS receiver in car
• Accuracy dependent on base station density– More precise in urban areas with more towers
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Towers tri-directional
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Cellular networks
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Cellular networks
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Cellular networks
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Triangulation
• Comparing signal strengths– Time delays
– Angles of arrival
– Three nearest towers
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Triangulation
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Cell Site Location Information
• Mobile switching centers may retain the location information in call detail records– At least for a period of time (e.g., 24 hours)
• Authorities can track subscriber’s general movements by following sequence of towers contacted by the phone
• May also obtain last recorded location before signal or power lost
NCJRL Judicial Conference April 2-3, 2012
Cell Site Location Information
• Most useful location information comes from initiation or receipt of a call or text
• A call data record (CDR) is kept for billing– Yield historical account of cell phone’s
locations
• Officers may also locate phone in “real time” while a call is in progress
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NCJRL Judicial Conference April 2-3, 2012
Enhanced 9-1-1
• FCC mandate of 95% of phones
• Locate phone location within 300 meters
• Within 6 minutes
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Beepers
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• Requires “tailing”– Antenna used to track radio signals
– Up to 5 miles
• Placed on car or package– 1”x2” to 3”x5”
• Does not store information
Beepers
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• Use beeps and/or lights to indicate– Direction (but not very well)
– Distance
Beepers
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GPS
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• Global Positioning System
• Developed by US government for military purposes– Cost unknown, but EU’s competing system
expected to cost around $25 billion
– Still operated by the military
GPS
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• Three Components– Satellites
•24 operational, 3 backups
•Any point on earth can “see” at least 6 at all times
•Each knows its distance from the center of the Earth
– Ground Stations•11 around the globe
– Receivers•Calculate their distance from the satellite
GPS
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GPS
Satellites
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GPS
• 32 Earth-orbiting solar-powered satellites– 24 in operation, plus spares
• Limited life span – about 10 years
• Equipped with up to 4 atomic clocks
• Orbits arranged so at least 4 (ideally 6) satellites “visible” anywhere, any time
• Send high-frequency, low-power radio signals
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GPS
Ground Stations
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GPS
• Ten ground stations around Earth – Monitor satellite signals and collect accuracy
measurements
• Master control station in Colorado – Determine if adjustments or updates needed
• Four large ground-antenna stations– Send corrective data and commands to
satellites
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GPS
Receiver
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GPS
• Equipped with quartz clocks constantly reset based on time signal from satellites
• Locate 4 or more (at least 3) satellites
• Calculate distance to each
• Use that information to deduce receiver location– Using “trilateration”
– In three-dimensional space
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GPS Devices• Portable
– Portable Navigation Devices•Vehicle•Outdoor
– Mobile phones
• Fixed– Vehicle– Marine– Aviation
• Tracking
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Trilateration
• 2-D– Signals from 3 satellites
– Latitude and Longitude
• 3-D– Signals from 4 or more satellites
– More accurate
– Lat/Long plus Elevation/Altitude
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2-D Trilateration
• Involves a bunch of difficult calculations
• Instead of learning that, let’s use pictures
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2-D Trilateration
Detroit
366 miles
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2-D Trilateration
Richmond
Detroit
312 miles
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2-D Trilateration
Richmond
Nashville
Detroit
Charleston
388 miles
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3-D Trilateration
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3-D Trilateration
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3-D Trilateration
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3-D Trilateration
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3-D Trilateration
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• Accuracy is limited by:– Earth’s atmosphere
•Weather generally has no effect– But doesn’t work underwater
– Structures, Terrain, Foliage
– Clock errors
– Gravitational effect on satellite orbits
GPS
NCJRL Judicial Conference April 2-3, 2012
• Generally, accurate to 15 meters
• Receivers use “Differential GPS” to calculate error– Makes measurement accurate to 10 meters,
but possibly up to 10 centimeters
GPS
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• Uses an assistance server to more rapidly or accurately obtain a location– Can be used in lieu of a fully functional GPS
receiver or can be used to enhance the accuracy of a location
• If the GPS receiver has trouble determining a location, A-GPS can make a connection using the cell network to send data
Assisted GPS (A-GPS)
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• Many cell phones use A-GPS, cell site triangulation and other technology to determine location
• Other benefits– Uses less battery power
– Less time to get a fix
– Better coverage
– System can be upgraded at network level
Assisted GPS (A-GPS)
NCJRL Judicial Conference April 2-3, 2012
Assisted GPS (A-GPS)
Satellites Phone Company’s Receiver
Smartphone
Cell Towers
A-GPSServer
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GPS Data
• Data that may be located on the GPS receiver includes:
• Device information
• Owner information
• Waypoints
• Home location
• Points of interest (POI)
• Deleted locations
• Last fix
• Routes/Journeys
• Track logs
• Favorites
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Digital Cameras
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• Pictures and video, of course– Geotagging
•Especially in smartphones
Digital Cameras
NCJRL Judicial Conference April 2-3, 2012
• Adds latitude and longitude coordinates to pictures and video– Stored in metadata; not visible in the image
• Usually derived from GPS– Camera must have a built-in GPS receiver
• Can also be used with text messages, social networking updates, and blog posts
Geotagging
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Geotagging
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Convergence
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Presented by
Don MasonAssociate Director, NCJRL
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