License to Track You

License to Track You



To locate a person who had been reported missing since days.


The only significant information available with the Cobb County Police Department in Georgia, USA, was the victim’s vehicle description and license plate number.

How was the Case Solved?

Police decided to use this information to get any lead in the case. It used License Plate Reader/Recognition (LPR) systems to see if the license plate had been captured by any LPR devices. “Upon querying the plate, we did find a sighting of the vehicle outside a town after the person went missing. We went to the location, and the vehicle was no longer there, but this piece of evidence prompted us to retrieve video footage from the store’s security cameras. A review of the video footage revealed two acquaintances of the missing person at the store with the latter’s vehicle. This was a major breakthrough in the case – the LPR detection told us exactly where to find the needle in a very large haystack,” explained Sergeant Larry “Ski” Szeniawski of the Cobb County’s Homicide Unit. The investigation then focussed on the two suspects, who were soon caught and confessed to having murdered the person.

How Does the LPR System Work?

LPR or Automated Number Plate Recognition (ANPR) is a system that captures images of vehicle license plates and converts the images into data that may be used for one or more applications. LPR system typically consists of a specialised LPR camera that incorporates both colour and infrared (IR) imaging. As the IR light illuminates the license plate, the cameras use video analytics to determine the presence of a vehicle based on the aspect ratio, size, shape and reflectivity of the license plate. In addition, a colour image is also taken simultaneously of the entire vehicle. All of this takes place in milliseconds. License plates can be read at a speed of up to 120 miles per hour. Most modern LPR systems can read up to 60 plates per second.

The image is processed by the OCR engine to generate an alphanumeric text interpretation of the license plate. The resulting plate read is then packaged with other information including the time and date stamp, GPS coordinates, a unique transaction identifier and the images themselves to complete the data packet. Each vehicle data packet is typically around 50 kilobytes in size and is transmitted back to a central software for the intended application (law enforcement, tolling, travel time information system, etc).

LPR cameras may be mounted on vehicles for mobile applications or on fixed structures such as bridges and gantries.

LPR for Law Enforcement in the US

In the application of law enforcement, all of the LPR data is sent into Vigilant Solutions’ secure law enforcement data center for use by over 30,000 law enforcement customers inside an investigative software suite known as LEARN (Law Enforcement Archival and Reporting Network). Over 2,500 agencies around the United States have account access into the software which gives them two primary benefits:

  • real-time alerting of vehicles of interest
  • investigative tools into historical LPR data


The investigative benefit of LPR technology is the most profound and has led to many major crimes being solved including homicides, rapes, child abductions, missing persons, identity theft, burglaries and theft, terrorism and much more. The investigative suite allows for law enforcement to query the system for locations of known fugitives, analyse pattern crimes (crimes that appear related) for the presence of common license plates at multiple locations, analyse a known suspect’s license plate to see what other license plates are frequently seen in close proximity to the suspect (giving possible associates), and much more.


“Without the original lead from the LPR data, it would likely have been a long time before the truck and body were discovered – at which point the likelihood of tracing this back to our two suspects would have been significantly reduced,” said Sergeant Szeniawski, adding, “The access to this kind of data helped us uncover a homicide and bring those responsible to justice.”