X
Get all access to the world's best video surveillance information.
Logo
680-70-2015-free-banner

Realities of License Plate Recognition (LPR)

by John Honovich, IPVM posted on May 08, 2008 About John Contact John

LPR is a very demanding application that can only succeed in limited operational conditions deployed by expert security integrators.

Historically, publicly available information clearly explaining the operational impact has been hard to find. Thankfully, Milestone has released their LPR administrator's manual providing an honest, clear and concise explanation. [Updated 2013 manual] Though this is for Milestone the points are generally consistent with the state of the art in currently available commercial systems.

The Milestone document helps to reveal 3 key practical elements:

  • LPR can only succeed when a number of strict operational conditions are met.
  • The costs of achieving these conditions makes LPR unfeasible for many scenarios.
  • You need deep security integration expertise to succeed but only modest IT depth.

The Conditions

Here are the key conditions that need to be meet in approximate order of difficulty:

US license plates need to be at least 130 pixels wide. This translates roughly into an image no wider than 5-6 feet assuming 4CIF standard definition video. That's a very tight shot.

  • The horizontal angle between the camera and plate is within 20 degrees. This means that if your camera is 10 feet away from the plate, the plate cannot be more than 3 feet to the right or left of the camera. This significantly limits where you can put the camera.
  • The vertical angle between the camera and plate is within 30 degrees. This means that if your camera is 10 feet away from the plate and the plate is 3 feet off the ground, the camera cannot be mounted than 8 feet high. This usually can be accommodated but is low relative to normal heights for outdoor surveillance.
  • There are a host of lighting adjustments that need to be made. Simply using a stock camera with stock settings will routinely cause very poor performance. For example, Milestone recommends CMOS cameras, disabling auto gain, using WDR and higher shutter speeds (if the car is moving). There is a lot of advanced details that need to be set correctly.
  • You must use MJPEG and you cannot use H.264 or MPEG-4. Since the analytics in this design are being done outside of the camera and since the analytic can only process images, MJPEG is required. You could theoretically use H.264 or MPEG-4 but then you would have to decode it and the processing power can be very significant. Bottom line is this can have a big impact on bandwidth utilization especially if you are looking for a wireless system.

Feasibility

Clearly, LPR is feasible for the traditional license plate camera use case: A camera installed immediately adjacent to an entrance or toll booth that is only a few feet off the ground and dedicated to looking at the plate. Automated LPR makes reading these plates easier.

However, for broader market usage, this has major limitations. Lots of companies like the concept of monitoring the license plates of people who enter their premises. Setting up cameras in the specific constraints required can be very expensive. Assuming you can find a location that meets these constraints, it requires a construction project that can be $5,000 or more per camera simply for the installation and equipment.

The holy grail is reutilizing your PTZs mounted on roofs and poles. However, these conditions should make it clear that is not feasible. One, getting the resolution needed would be difficult. Does a monitor manually zoom in on license plates? Even if he does, what will the image quality be, given the lighting constraints required for LPR. Also, it will be extremely tough to stay within booth the horizontal and vertical angle requirements.

LPR analysis, with its current capabilities, cannot enable significantly new operational uses of license plate monitoring. While it should help with the traditional use case of monitoring controlled traffic flow, its constraints make it very challenging for broader use.

Security Integration Expertise

The other interesting element that the Milestone manual demonstrates is that LPR integration does not demand deep IT skill but it does demand deep expertise in security design and camera systems.

Integrating LPR is much more like using a graphics design application than it is like setting up a mail server. It depends on understanding the design objectives of security, the physical conditions of the site and the capabilities of the video tools available. The IT elements of the setup are fairly straightforward for a security integrator. The challenge lies in the design and application.

Finally, it is great that Milestone released this manual. Milestone has clearly shared operational limitations that might stop some from buying their product. It is hard for most organizations to do this. Nevertheless, in the long run, it is better for our customers and I believe better for Milestone. In this way, we can maximize the probability that projects will be successful, customers will be happy and the market expands over time.






Most Recent Industry Reports

Milestone LPR Tested on Mar 31, 2015
How well does Milestone's LPR work? Milestone's LPR supports off the shelf IP cameras, integrating license plate recognition with the Milestone Smart Client for live video, playback, and alar...

4K Panasonic Tested (Panoramic) on Mar 25, 2015
Panasonic has released their first 4K cameras, and surprisingly, they are panoramic, which they tout include high sensitivity 1/2" image sensors, true WDR, auto back focus, and other feat...

IP Networking Book Released on Mar 23, 2015
This is the first ever IP Networking Book for Video Surveillance. The book will give you the knowledge and the confidence to make the right decisions when designing and deploying video surveillanc...

Member Invites Released on Mar 18, 2015
Members ask regularly how can they share IPVM content with their customers, colleagues, friends, etc. Now, we are introducing 'invites' that allow eligible members to give 1 month free IPVM member...

Axis vs Hikvision vs Sony Encoder Test on Mar 18, 2015
In this report, we share test findings of three popular four port analog SD encoder models: Axis P7214 Hikvision DS-6704HFI Sony SNT-EX104 Below, we share our findings in areas including: ...

Remote Network Access for Video Surveillance on Mar 13, 2015
Remotely accessing video is difficult for 3 reasons. Private Networks Almost all video surveillance uses private IP addresses, that are by definition, not accessible directly over the public Inte...

TCP vs UDP for Video Surveillance on Mar 11, 2015
TCP or UDP? What should you use for video surveillance? TCP and UDP are both in use in the video industry today, each with strengths and weaknesses when it comes to live viewing, playback, error ...

CBR vs VBR vs MBR - Surveillance Streaming on Mar 11, 2015
How you stream video has a major impact on quality and bandwidth. And it is not simply CODEC choice (like H.264, H.265, MPEG-4, etc.) However, regardless of the CODEC, one still needs to choose ...

Tyco / Exacq Illustra Cameras Tested on Mar 09, 2015
Prior to Tyco acquiring them, Exacq was one of the leading independent VMSes. Now, Tyco / Exacq is becoming a 'solution' provider, billing their Illustra cameras as: "The Easiest High Defini...

NMAPing IP Cameras on Mar 05, 2015
The Hikvision hack has increased security concerns. Indeed, most users do not know whether they are vulnerable or not, which ports of their systems are open, and what services they may be running,...