Terrorists were the intended targets for the first license plate
readers deployed by New York City. It was 2006 and the NYPD was involved
in what was known as the Lower Manhattan Security Initiative, a
counter-terrorism plan that involved setting up movable, random roadblocks in
the Financial District. Thousands of cameras provided ancillary surveillance in
the area south of Canal Street but the program revolved around special ones
equipped with license plate reading technology.
Thank goodness the NYPD has been successful so far in quelling
terrorist plots. They have expanded their use of license readers to attack
everyday crime wherever it may be happening. According to an article in the New
York Times, as of April 2011, New York was using 238 license plate readers. Of
these 130 are mobile, mounted on the backs of police cars that might be patrolling
any street in the city’s five boroughs. The other 108 are fixed posts at city
bridges and tunnels, as well as above other thoroughfares. License plate
reading cameras differ from other surveillance IP cameras that monitor broad
areas in that they are designed to focus on a small area, and are aimed low to
the ground.
Police tracked down 3,659 stolen vehicles, and issued traffic
tickets for 34,969 un-registered ones. In the period from 2010 to 2011 alone,
they identified and recovered 248 vehicles bearing stolen license plates.
Divisions dealing with felonies have used the technology to
their advantage as well. In 2011 a bank robber was apprehended after
high-jacking a livery cab in New Jersey and driving it through the Lincoln
tunnel to New York. Somewhere along the route, the license plate was detected
and the car traced to a specific block in Queens. FBI agents, alerted by the
NYPD, surveyed the block and the next morning apprehended the suspect who had a
loaded pistol in his possession.
In another case of violent crime, a murder suspect was arrested
after several cameras spotted his plates in various locations. The police had
but to connect the dots to find him sequestered in a closet in a relative’s
home.
How does this work in a city measuring 304.8 square miles (or
468.9 square miles if one counts the 165.6 square miles of water)? The data
captured on the cameras are continuously checked against specific databases
containing information on stolen vehicles, stolen license plates, and unregistered
vehicles. In addition, the cameras’ files are downloaded twice daily to central
computers where personnel update the databases each time. Investigators are
then able to retrieve new information such as the license plate of a new
suspect or the stolen license plate of one they’ve lost track of.
Technology Highlights:
This technology is gaining popularity in security and traffic installations. The technology concept assumes that all vehicles already have the identity displayed (the plate!) so no additional transmitter or responder is required to be installed on the car.
The system uses illumination (such as Infra-red) and a camera to take the image of the front or rear of the vehicle, then an image-processing software analyzes the images and extracts the plate information. This data is used for enforcement, data collection, and (as in the access-control system featured above) can be used to open a gate if the car is authorized or keep a time record on the entry or exit for automatic payment calculations.
The LPR system significant advantage is that the system can keep an image record of the vehicle which is useful in order to fight crime and fraud ("an image is worth a thousand words"). An additional camera can focus on the driver face and save the image for security reasons. Additionally, this technology does not need any installation per car (such as in all the other technologies that require a transmitter added on each car or carried by the driver).
- Automatic Vehicle Identification (AVI)
- Car Plate Recognition (CPR)
- Automatic Number Plate Recognition (ANPR)
- Car Plate Reader (CPR)
- Optical Character Recognition (OCR) for Cars
Does it Work?
Early LPR systems sufferred from a low recognition rate, lower than required by practical systems. The external effects (sun and headlights, bad plates, wide number of plates types) and the limited level of the recognition software and vision hardware yielded low quality systems.
However, recent improvements in the software and hardware have made the LPR systems much more reliable and wide spread. You can now find these systems in numerous installations and the number of systems are growing exponentially, efficiently automating more and more tasks in different market segments. In many cases the LPR unit is added as retrofit in addition to existing solutions, such as a magnetic card reader or ticket dispenser/reader, in order to add more functionality to the existing facility.
Even if the recognition is not absolute, the application that depends on the recognition results can compensate the errors and produce a virtually flawless system. For example, when comparing the recognition of the entry time of a car to the exit time in order to establish the parking time, the match (of entry verses exit) can allow some small degree of error without making a mistake. This intelligent integration can overcome some of the LPR flaws and yield dependable and fully automatic systems.
Some license plate recognition system uses
special software who automatically reading license plates.
· Image analysis
· Image and data storage
· Data transmission
License plate capture cameras with
CCD image sensor works with a pulsed infra-red light source to monitor a target
area of passing vehicles. The illumination device contains up to 190 LEDs in
the near infrared range and is capable of providing a high contrast black and
white image similar to the image below.
Notice how the use of infra-red light suppresses most of the
surrounding detail and allows the reflective license plate properties to make
it dominant in the field. In addition the TruViewLPR license
plate capture camera lets the user alter the contrast by changing each video
field up to sixty times per second, on a cycle of three different levels of
brightness - low, medium, and high. Taken together, these allow for
optimal plate image processing no matter what the time of day or the condition
the license plate in question.
The captured images are processed by a set of algorithms that extract only the
license plate portion of the frame and send it to two different Optical
Character Recognition engines for processing. It takes 200 milliseconds
or less for the LPR Software to analyze and come up with an ALPR result. It
then reports one of two reads: The read that provides the highest confidence
score level of all the captured images for that particular license plate or the
read that meets a pre-determined minimum level of confidence.
The image with the best results is now saved and linked with the results data.
The data might consist of the plate number, the date and time, the lane number.
In addition another camera may be used to furnish a scene overview showing a
full view of the vehicle which will be linked to the plate data and image, all
to be stored to be made available for subsequent queries. You can also
add many IP cameras for
multiple overviews when using VMS software.
Data and Image Management and Display
Stored data can be forwarded to a central server over a standard TCP/IP
connection or using a wireless connection.
The LPR information can be displayed using Ocularis VMS software or using the
Central Management console which will allow an operator to bring up ALPR events
based on license plate number, date, time, lane, or other desired
characteristics.
There are a number of applications where
automated License plate recognition can be used. Image collection can
take place in a triggered or non-triggered environment.
· A
non-triggered installation needs no detection device. In this mode, software,
known as Virtual Vehicle Detector, analyzes each image at a rate of
sixty images per second for the presence of a license plate. This image, and
additional images containing the vehicle’s license plate data is captured and
processed to extract the license plate characteristics
· A triggered mode requires a
detection device and can be used in a number of applications. The trigger could
be an in-ground loop or an optical trigger and is called for when several
systems are to be tied together to a single event. Such parallel systems might
be a vehicle classification system, a transponder system, a parking lot ticket
dispenser, a weigh-in motion system , and so on.
The LPR Software device can act as a lane controller, hosting a
database that will permit or deny vehicle access into or out of a parking
facility, gated community, or high-security compound. This can be done with the
optional Universal Interface Controller (UIC) to provide
contact closure outputs to open or close a gate or arm in response to queries
of the database.
And so in this day and age, a license plate serves as more than
just a way to determine if that’s your buddy in the silver Honda up
ahead.
LPR systems normally consist of the following units:
- Camera(s) -
that take the images of the car (front or rear side)
- Illumination - a
controlled light that can bright up the plate, and allow day and night
operation. In most cases the illumination is Infra-Red (IR) which is
invisible to the driver.
- Frame
grabber - an interface board between the camera and the PC,
allows the software to read the image information
- Computer -
normally a PC running Windows or Linux. It runs the LPR application which
controls the system, reads the images, analyzes and identifies the plate,
and interfaces with other applications and systems.
- Software - the
application and the recognition package. Usually the recognition package
is supplied as a DLL (Dynamic Link Library).
- Hardware -
various input/output boards used to interface the external world (such as
control boards and networking boards)
- Database - the
events are recorded on a local database or transmitted over the network.
The data includes the recognition results and (optionally) the vehicle or
drver-face image file
The following illustration shows a typical configuration of a LPR system (for
example, for 2-lanes-in and 2-lanes-out access control system). The system
("SeeLane") is a typical example of such system.
The SeeLane application runs as a background Windows application in the PC
(shown in the center), and interfaces to a set of SeeCarHead
camera/illumination units (one for each vehicle) which are interfaced by the
frame grabber. The application controls the sensors and controls via an I/O
card that is connected thru a terminal block to the inputs and outputs.
The application displays the results and can also send them via serial
communication and via DDE messages to other application(s). It writes the
information to local database or to optional remote databases (via the
network).
LPR applications have a
wide range of applications, which use the extracted plate number and optional
images to create automated solutions for various problems. These include the
following sample applications
Parking - the plate number is used to automatically enter pre-paid
members and calculate parking fee for non-members (by comparing the exit and
entry times). The optional driver face image can be used to prevent car
hijacking.
In this example, a car is entering a
car park in a busy shopping center. The car plate is recognized and stored.
When the car will later exit (through the gate on the right side) the car plate
will be read again. The driver will be charged for the duration of the parking.
The gate will automatically open after payment - or if the vehicle has a
monthly permit.
Access Control - a gate automatically opens for authorized members in a
secured area, thus replacing or assisting the security gaurd. The events are
logged on a database and could be used to search the history of events.
In this example, the gate has just been automatically raised for the
authorized vehicle, after being recognized by the system. A large outdoor
display greets the driver. The event (result, time and image) is logged in the
database.
Tolling - the car number is used to calculate the travel fee in a
toll-road, or used to double-check the ticket.
In this installation, the plate is read when the vehicle enters the toll
lane and presents a pass card. The information of the vehicle is retrieved from
the database and compared against the pass information. In case of fraud the
operator is notified.
Border Control - the car number is registered in the entry or exits to the
Country, and used to monitor the border crossings. It can short the border
crossing turnaround time and cut short the typical long lines.
This installation covers the borders of the entire Country. Each vehicle is
registered into a central database and linked to additional information such as
the passport data. This is used to track all border crossings.
Stolen
cars - a list of stolen
cars or unpaid fines is used to alert on a passing 'hot' cars. The 'black list'
can be updated in real time and provide immediate alarm to the police force.
The LPR system is deployed on the roadside, and performs a real-time match
between the passing cars and the list. When a match is found a siren or display
is activated and the police officer is notified with the detected car and the
reasons for stopping the car.
Enforcement - the plate number is used to produce a violation
fine on speed or red-light systems The manual process of preparing a violation
fine is replaced by an automated process which reduces the overhead and
turnaround time. The fines can be viewed and paid on-line.
The photo is an example of a speeding car caught by the traffic camera. The
rear vehicle plate is automatically extracted off the scanned film image,
replacing a tedious manual operation and the need to develope and print the
violation. The datablock on the top-right side is additional speeding
information that is automatically extracted from the developed film and used to
complete the fine notice and inserted to a database. The violators can pay the
fine on-line and are presented with this photo as a proof with the speeding
information.
Traffic control - the vehicles can be directed to different lanes according
to their entry permits (such as in University complex projects). The system
effectively reduces traffic congestions and the number of attendents.
In this installation the LPR based system classifies the cars on a congested
entrance to 3 types (authorized, known visitors, and unknown cars for inquiry)
and guides them to the appropriate lane. This system reduced the long waiting
lines and simplified the security officers work load.
Marketing Tool - the car plates may be used to compile a list of frequent
visitors for marketing purposes, or to build a traffic profile (such as the
frequency of entry verses the hour or day).
Travel - A number of LPR units are installed in different locations
in city routes and the passing vehicle plate numbers are matched between the
points. The average speed and travel time between these points can be
calculated and presented in order to monitor municipal traffic loads.
Additionally, the average speed may be used to issue a speeding ticket.
In this example the car is recognized at two points, and the violation shows
the photos of both locations which were taken on bridges on top of the highway.
The average speed of the car is calculated from both points, and displayed if
the speed passed a violation threshold, and optionally printed.
Airport Parking - In order to reduce ticket fraud or mistakes, the LPR unit
is used to capture the plate number and image of the cars. The information may
be used to calculate the parking time or provide a proof of parking in case of
a lost ticket - a typical problem in airport parking which have relatively long
(and expensive) parking durations.
This photo shows the gate of a long term airport parking. The car is recognzied
on entry and the data is later used to track the real entry time in case of a
lost ticket.
