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Will My License Plate Recognition System Work in Snow?

Snow happens whether you like it or not.  As winter approaches, clients are asking whether their license plate recognition system will still provide data when the weather turns bad.  Some systems are unreliable – they’re real flakes. 

You don’t want to get caught in the dead of winter with an ALPR system that’s under the weather.  Let’s look at the facts before you get past the point of snow return.  And if you like snow puns, prepare to laugh your sled off.

License Plate Recognition System Winter Snow

Audi breezing through the snow.  Source: Unsplash.

How Do License Plate Recognition Systems Work

If you’re just starting to explore ALPR technology, you might not know the frost thing about how license plate recognition systems work.  There are a lot of myths about ALPR software and there’s also a lot of variation between brands. 

Just like a snowflake, every license plate is one of a kind, and getting accurate data is the key to obtaining a flurry of insights. LPR systems take in and make sense of data in stages:

  • Image Capture – IP cameras capture an image or video of traffic.  When there is enough light, the license plate is unobscured and the vehicle is moving at low speeds, most cameras work fine, but low resolution, low light, high speed and bad weather can all fool some systems.
  • Plate Detection – Cameras offer the image or video frame to the license plate recognition system for analysis.  You can imagine how a vehicle covered in snow might create challenges when it comes to plate detection.  Our intuitive and powerful machine learning algorithm uses context to “look” in places license plates are likely to appear.  It corrects for odd angles and sizes, filters out anomalies and disregards unrelated text.
  • Character Isolation – Human eyes see individual characters on a license plate, but teaching software to do the same is snow joke!  A good license plate recognition system separates each individual number, letter or symbol.
  • Character Recognition – ALPR engines then match lines, curves and patterns in the image to letters and numbers.  Plate Recognizer’s software is so smart it doesn’t just know the Latin alphabet, it knows the Thai alphabet and decodes German umlauts in license plates!

With so many stages involved, you can see how something might go wrong.  Even light flurries make it harder to see, and heavy snow blankets everything.  We knew when we started that weather creates challenges, so we built our license plate recognition system to give clients the best possible performance in all environments. 

We came, we thaw, we conquered.

Number Plate Recognition System Snow

Range Rover covered in snow.  Source: Unsplash.

Factors That Influence ALPR Performance

People use the data they gather using our LPR system to:

You can imagine how important accuracy is in every instance.  If a police department’s license plate recognition system fails in bad weather, it’s not “see snow evil, hear snow evil.”  Criminals might go free and innocents might suffer.  If icy conditions keep your ALPR system from sending notifications for curbside pickup, you could have angry customers and bad reviews. Things can quickly snowball out of control.

The International Association of Chiefs of Police submitted an extensive report to the U.S. Department of Justice detailing factors that cause problems with LPR systems.  

The top problems for license plate recognition systems were dirty or bent plates, physical obstructions (anything between the camera and the vehicle) and unusual plate design.  Any of these factors might cause the organization gathering the data to receive misreads, or the system might not give any data at all. It’s a slippery slope.

Beautiful drive through the snow at sunset. Source: Unsplash.

Will My License Plate Recognition System Work in Snow?

So, does your license plate recognition system have a snowball’s chance of providing you with the data you pay for this winter?  That depends both on the quality of the software you use and whether or not license plates are visible to the eye.

If you’re comparing Plate Recognizer and other ALPR system providers, know that software capabilities change all the time.  Whatever company you choose, it’s wise to ask ahead of time what you can expect in terms of bad weather performance.  Here are a few of the results that came from testing our ALPR.

License Plate Recognition System Blizzard

Bad weather did not stop our ALPR from capturing this plate correctly.  Source: Online.

It was snowing pretty heavily when this photo was taken.  The photo was taken with the plate at an angle, and there was also a bumper sticker on the car, a feature that confuses some LPR systems.  Our software provided the correct data, reading ZH360172.

License Plate Recognition System Heavy Snow

Heavy snow conditions but the plate is pretty easy to see and quite easy for Plate Recognizer to decode.  Source: Online.

This Chevy with Texas plates might have had trouble on icy roads, but our ALPR had no trouble with decoding the license plate despite limited visibility.

License Plate Recognition System Heavy Snow

Snow and low light sometimes come hand in hand.  We got it covered.  Source: Online.

Snowy days can be dark and dreary, and low light is a challenge for some license plate recognition systems.  Plate Recognizer confidently reported this Toyota’s plates despite the dim environment.

License Plate Recognition System at night Snow

Another example of a challenging light condition for ALPR.  We got this one too!  Source: Online.

As it snow happens, low resolution photos and reflectivity confounds some ALPR systems.  Plus, when the weather is messy, precipitation can get on the camera lens to cause further complications.  In the above image, Plate Recognizer “sleighs” all challenges to correctly decode the plate as X97JSU. 

And snow on and snow forth.  Our algorithm handles license plates that are blurry, dark, angled, bent, and moving quickly.  We even have a solution for vehicles without license plates.  Plus, our ALPR is so fast some others could be described as glacial.

About to take on the snowy mountains.  Source: Unsplash.

So Is Plate Recognizer 100 Percent Accurate?

With great powder comes great responsibility.

No license plate recognition system is 100 percent accurate all of the time. Plates have to be visible for our system to work.  In most cases if human eyes can decode the plate, Plate Recognizer can too.  Our engine does well even in blizzard conditions as long as the snow does not cover up the plate.

Number Plate Recognition System Heavy Blizzard

This was a really tough license plate to read.  Hopefully in a future version, we can tackle this. Source: Online.

For example, in this photo snow almost completely covers the plate, and both snow and fog are present.  Unfortunately, our engine (as of Oct 8, 2021) was not able to decode the correct license plate from this image. 

Still, Plate Recognizer often gets results even when license plates are partially obscured.  For the following image, our license plate system correctly reported DKJ678

License Plate Recognition System Winter Conditions

Plate and image are quite blurry.  Our ALPR engine conquered the day. Source: Pixabay.

Customer Support All Winter Long

What happens if you run into a problem or have a question in the dead of winter when even Jack Frost would rather not show up to work?  Even when the weather outside is frightful, our customer support team is here for you.  We respond to inquiries and requests within 12 – 24 hours, even on weekends.

VW Touareg pausing on the side to admire the beautiful snow ahead!  Source: Unsplash.

And trying Plate Recognizer is a snow brainer.  Sign up today for a free ALPR trial to test drive our developer-friendly license plate recognition system that works in all environments, even heavy snowy conditions!

Warning!  We won’t be able to tackle ALPR for this vehicle below.

License Plate Recognition System Snow

Entire car is covered in snow!  For sure our ALPR cannot read this.  Source: Unsplash.

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About Plate Recognizer

Plate Recognizer provides accurate, fast, developer-friendly Automatic License Plate Recognition (ALPR) software that works in all environments, optimized for your location. Sign up for a Free Trial!