Frequently Asked Questions


ALPR cameras are a niche market within the CCTV market. They are a niche because they demand a number of additional functions over and above anything that mainstream CCTV cameras can provide.

If you are thinking of buying ALPR cameras, there are a number of vital pieces of information that you should consider and ask your potential supplier for information about the product they are offering you.

General FAQS

We know that a lot of people have some general questions regarding ANPR cameras and their usage, we hope we have provided you with some of the key answers.

How do the Police use ALPR/ALPR?

Police across the world use ALPR/ALPR cameras for a wide variety of reasons due to the flexibility that ALPR/ALPR technology provides. Police Force can use ALPR/ALPR technology to identify uninsured drivers, vehicles which are not road worthy, speeding vehicles (when used alongside suitable radar equipment) and identify vehicles of interest which may be linked to a crime or be potential threats. The use of ALPR/ALPR technology is to support the Police in keeping the roads safer and offering another tool in the identification of criminal movements or provide the opportunity to stop criminal activity before it even begins.

It is important to note that each Police Force has stringent regulations about the use of ALPR/ALPR technology, as well as the storage and use of any information gathered. If you would like to know more about the use of ALPR/ALPR technology by Police in your area it is best to review the regional policies of your Police Force which can often be found on their website.

Do ALPR Cameras record speed?

Although ALPR/ALPR cameras are used to support the identification of speeding vehicles, they cannot perform speed identification without the inclusion of radar equipment. Some high specification ALPR/ALPR cameras, such as those designed by MAV systems, can be used alongside radar equipment to collate information and provide an ‘evidence pack’ which gives the speed of a vehicle alongside specific details of the vehicle and it’s location. This provides the user with the necessary information to take action and supports the objective of making the world’s roads safer.

Are ALPR Cameras only on motorways?

Though ALPR/ALPR cameras are used on motorways and highways, these are not the only place they are found. ALPR/ALPR cameras are used for multiple reasons and therefore can be found at the heart of many systems located in varying positions. The high performance ALPR/ALPR cameras designed by MAV systems can be found in a wide range of solutions including;

  • Car parks across the world to support the efficiency of car park management
  • Cities throughout the world to support civil enforcement and reduce risk to other vehicles and pedestrians
  • Weighbridges to collate vehicle data
  • Police cars to identify vehicles on a watch list
What is ALPR?

Automatic Number Plate Recognition (ALPR) is a highly accurate system capable of reading vehicle number plates without human intervention through the use of high speed image capture with supporting illumination, detection of characters within the images provided, verification of the character sequences as being those from a vehicle license plate, character recognition to convert image to text; so ending up with a set of metadata that identifies an image containing a vehicle license plate and the associated decoded text of that plate.

People often refer to the ALPR process as OCR (Optical Character Recognition) but this really does not do justice to the full chain of technologies that are involved in getting license plate reads from very complex images.

How are ALPR cameras being used?

ALPR cameras have a number of practical applications in car park management, tolling, bus lane enforcement, Intelligent Transport Systems (ITS) and law enforcement (see more about these here). They are used to enforce the rules of the road as well as provide important information regarding traffic flow enabling measures to be taken to reduce driver’s journey time. They are also used to identify cars that should not be on the road as well used to support the deterrence, disturbance and detection of criminals.

How are ALPR cameras different from CCTV cameras?

Whilst CCTV cameras provide an ongoing recording of movements, they are not designed to capture specific information for any given setting. ALPR cameras are designed to read and capture number plates at varying distances and then refer that information back to a software system which deals with the information in varying ways depending on the objective of the systems. For instance, in car parking it can be relayed to software which allows automatic entry and exit to a car parks or used by police to alert them as to a ‘car of interest’ via their internal software systems.

Who uses ALPR cameras?

ALPR cameras are used by a variety of sectors including, car park management, Intelligent Transport Systems (ITS), Police, Military, Councils and Governments. Each sector will have different uses for the cameras but this will be achieved using different types of software and systems integrated into their own processes.

Is it likely that my number plate has been scanned?

Yes. ALPR systems are part of the network of security and surveillance cameras around the road infrastructure. ALPR systems are not installed without good reason – they cost business and government money to install and maintain and so they are normally only put up where there is a good business case. Police use ALPR cameras to scan number plates across the world in an attempt to identify ‘cars of interest’ which may belong to a criminal at large or someone that has not insured or taxed their car. Whilst you will fit into none of these categories, your number plate will most likely have been scanned during a sweep to find those that do. ALPR cameras are also used by other sectors to monitor traffic, bus lane usage, tolling and provide efficient services in car parks which are other reasons that your number plate may have been scanned.

Do they keep my number plate scan and any pictures of me?

The majority of number plates that are read will be deleted after initial checking if they do not need to be retained for valid investigations or evidential purposes. Storing data costs money and so, in the majority of cases commercial ALPR users want to actively delete data that they do not require, especially any images that accompany the plate read as the images are large and therefore fill storage quickly and generally need to be purged. Any images that are retained are subject to data protection legislation in the country of use which normally prohibits any dissemination of images without due cause.

What has using ALPR cameras achieved?

ALPR cameras have assisted police in the capture of hundreds of criminals and provided support in the tracking of lost persons and stolen vehicles. They provide information that enables police to stop cars that should not be on the road and remove dangerous drivers from the road.

In addition, ALPR cameras provide ‘real time’ information regarding traffic and allow for measures to be taken to reduce journey time for travellers.

More and more parking areas also provide an automated service for users via ALPR cameras enabling a more efficient use of parking facilities.

Are ALPR cameras used in most countries?

They are used in most countries to support the justice system as well as provide security, information and guidance regarding traffic, journey time, car parks, ports, weigh bridges and emission zones. ALPR cameras exist as a supportive tool within most countries throughout the world although the extent to which this technology is used changes per country.

What does the scan reveal about me?

Number plate scans are often used to analyse journey times, provide ease of payment in car parks, identify misuse of bus lanes and support traffic analysis, on each occasion your number plate is just used as a indicator of your movements and as such no personal information is available until the point of issuing of penalty notices. When used by the police, scans are used to check on the legality of your car being on the road i.e. tax and insurance and whether any outstanding warrants are out on the car owner. No personal information is viewed unless required due to the existence of criminal evidence and even then it is only available to those with specific clearance who can only view the information under specific circumstances and strict guidelines.

Can ALPR cameras read all number plates?

In general, if a license plate is visible to the human eye, then camera technology can also capture it.  Since display of license plates is law in almost every country then the ability to track a vehicle from the image is also possible. In regards to European plates, the best ALPR cameras accurately read over 95% of number plates scanned perfectly without any intervention. Some systems can approach the ultimate target of 100% but normally this is impractical due to defects or obscuration of part of the plates.

It should be noted that the best ALPR systems can also detect vehicles where no plate is visible or one has been corrupted. These plates can be reviewed by human operators or secondary ALPR systems if necessary (e.g. to support evidence of an offence) and so evasion of ALPR systems by modification of license plates is not only illegal but also normally futile.

Why are ALPR cameras more expensive than CCTV cameras?

ALPR cameras are a niche within the CCTV market and demand higher pricing than conventional cameras because of their additional features and the fact that they are sold in lower volumes than mass market CCTV models. Conventional CCTV cameras cannot provide professional grade ALPR for day and night operation on moving vehicles.  This is to be expected as the vast majority of CCTV users are looking for very different image handling characteristics than is appropriate to ALPR users.  This means that ALPR cameras must be designed specifically for the market and use high grade components and modules to provide 24/7 images.

For the professional ALPR sector, the cameras normally include:

  • pulsed illumination
  • controlled exposure time
  • high quality raw images
  • optical filters
  • long life and reliability
  • low maintenance design
  • rugged enclosures
  • hermetically sealing

These features are not available as a package through normal CCTV products.

Why choose an Intelligent ALPR Camera?

Intelligent cameras dramatically reduce the bandwidth required to be transferred over networks by dealing with the high definition images at the camera itself and only sending the images and metadata for each plate read. Performing the recognition at the edge also reduces cabling, data costs and storage costs.

Specifically, the Rapier 50IQ incorporates HD image quality, motorised zoom cameras, high speed ALPR recognition and maxIRange™ pulsed IR lighting in one efficient unit. A perfect balance of low power consumption and superior performance capabilities, coupled with the latest generation of ALPR engine and simple installation takes intelligent cameras to the next level.

Technical FAQS

To provide you with further support we have highlighted some questions we are often asked regarding technical aspects of our cameras.

Do ALPR/ALPR Cameras work at Night?

Whether an ALPR/ALPR camera can work at night is dependant on the quality of the ALPR/ALPR camera itself. Some ALPR /ALPR cameras, like those built by MAV Systems, include Infra-Red (IR) as well as illuminators to provide excellent performance in both day and night. High specification ALPR cameras, such as the IQ and IQX ranges, ensure full 24 hour a day performance and high level accuracy no matter the lighting or weather conditions.

Is a varifocal lens the same as a motorised zoom?

No. A varifocal lens requires the installer to be able to make small adjustments to focus and zoom when the camera is in situ by moving the lens assembly by hand. This can mean that the installer has to take the camera apart to expose the varifocal lens and then adjust the available trims whilst up a ladder, in a cherry picker, on a gantry whilst also looking at a live image or ALPR capture. It is inappropriate to open cameras on site, against good engineering practice and would contravene health and safety assessments unless multiple staff are onsite. More to the point, it is not required since motorised zoom cameras allow all adjustments, especially the vital fine adjustments to be made safely in controlled conditions without exposing the camera’s internal electronics – more on this below.

Does the motorised lens do more than a varifocal or fixed lens?

Yes.  There are a host of features that a motorised lens will permit that have real and valuable benefit to any ALPR camera user.  Nearly every Rapier 30/50 user has commented that the software controlled setup of the camera has lowered their cost of installation and is now capable of being done by staff with minimal training required.

  1. Easy setup with software assistance – The Rapier 30 and 50 cameras have both been calibrated to permit real-life settings to be deployed within seconds. Not only can the camera be zoomed to exactly the right field of view for the target distance but, more importantly, the focus at that point can also be set without the need to actually have objects in view. This needs to be thought about to fully understand just how valuable this can be. Imagine you are setting up an ALPR camera on a busy lane of traffic. Focussing on moving traffic is hard, you can’t stop the traffic or have a colleague stand in the road with a license plate, so what do you do? With Rapier 30 or Rapier 50 you just tell the setup software the distance you want to operate at and it will immediately go to the correct zoom level and focal plane – job done!
  2. Repeatable settings that can be interrogated and stored – When a camera needs to be substituted due to damage or for redeployment, the original settings can be uploaded into the substitute camera and immediately take on the exact equivalent purpose.
  3. Perfect field of view in small steps – The motorised lens has over 2000 selectable zoom positions between the wide angle and telephoto. By contrast, a fixed lens is normally only available in large jumps of field of view, e.g. 25mm, 16mm, 12mm.
  4. Only one spare camera for all locations – Whereas fixed lens cameras can offer a purged environment because they require no installer changes they have the disadvantage of being fixed as the name implies. Therefore, on any normal site where multiple target distances exist, only zoom or varifocal cameras allow substitution – and only motorised zoom ones offer the ability to quickly substitute from preset memories.
Why is a controllable zoom, focus and iris important?

The majority of Rapier cameras are fitted with motorised zoom, focus and iris controllable lenses. This allows the settings of the distance for accurate plate reading to be optimised without the need to open the camera’s enclosure to access a varifocal lens.

This means that cameras can be trimmed to the exact situation at any time even after installation by using the camera’s control protocol.  For some HD cameras, MAV supply these with fixed lenses that are preset to cover the full range of ALPR read positions from the factory with no on-site adjustments required to the camera lens.

Rapier cameras are hermetically sealed to IP68 which means that we allow no physical access to the internal electronics and optics and use software control to achieve perfect ALPR settings quickly and repeatedly.

What does IP68 hermetically sealed rating mean?

ALPR cameras have the potential to suffer from water and water vapour ingress more than other forms of CCTV camera and need to be treated differently in their construction. MAV believe that the only way to ensure your system is built to last 5+ years of 24/7 service is to hermetically seal the camera to IP68.

Sealing involves design of the camera with waterproof and vapour proof gaskets and connectors followed by purging of the cameras to expel the moisture within them at the time of manufacture. The moisture is removed using specialist equipment which continues to remove moisture until the equipment has a dew point that will not allow condensation within the unit to very low temperatures.

MAV can thereby warrant that they will not suffer water/moisture ingress issues under a wide variety of operating conditions.

What does a few point of actually mean to the user?

The Dew Point is the temperature at which the air will release the moisture it contains and lead to condensation forming. All Rapier cameras are purged to a level of -30°C (-22°F) or lower as their internal air Dew Point.

This means that unless the temperature of any surface within the camera drops below the dew point level then there will be no condensation on the camera lenses or circuitry. This does not mean that the ambient temperature cannot drop below this temperature since, within the Rapier, the heat from the camera modules and illumination will raise the internal temperature above ambient.

In practice, MAV can take the dew point within Rapier cameras as low as -40°C (-40°F) just by continuing the same purge process for longer and have done so for customers operating in extremes of low temperature.

Is it enough to know that a camera is dry-air or Nitrogen purged?

No.  Just because the supplier has dry-air purged the equipment this does not mean that they can prove that it is leak-proof.  Only by using the type of specialist kit that MAV use will the supplier be able to prove that the camera is leak-proof – just blowing dry air into a sealed unit proves nothing.

The recognised standard to prove compliance is to measure the ‘Dew Point’ of the air within an enclosure as described above.

How do manufacturers know if their camera leaks water or moisture?

MAV 100% test every camera to prove that it has no leaks on the seals between metalwork and glass by conducting a pressure test on every Rapier camera we manufacture. There is no way of knowing if your product leaks unless you do this test. If you don’t leak air, you won’t allow either moisture or water to enter. Manufacturers who allow air to enter by using breather vents or pressure equalisation techniques generally do not test their cameras for leaks – if they did then they would probably purge at the same time. So, if you buy a camera with a breather on it, there is probably no way that you or the manufacturer can say whether the unit is actually sealed from ingress of rainwater never mind vapour.

When does the 'breathing' that allows moisture ingress happen on competitor cameras?

The points at which air flows in/out of an unsealed or ‘vented’ camera can be as regular as daily when there are temperature changes between day and night that lead to air pressure changes. A more dramatic version will also happen during air transit where the pressure drops in the cargo hold and can actually inject high moisture content air (cloud) during landing.

Is IP67 a gurantee of no moisture ingress?

No, IP67 only means that water droplets will not enter the camera but it does not mean that water vapour cannot enter. Indeed, many IP67 enclosures have ‘breather’ vents that allow air to enter and leave the enclosure so as to allow pressure equalisation. The classic example of this is provided by Gore products which have been utilised in clothing and industrial situations to stop water entering an enclosure but allowing air to move in and out. For clothing, this prevents rain from penetrating the outer skin but has the added benefit of allowing moisture (body heat/perspiration) to vent out – so reducing humidity within. However, the moisture transfer and water protection is not a one-way process – the barrier material both prevents water and allows air to move in BOTH directions. This feature is the potential killer for ALPR cameras because this ventilation method simply acts as a slow buildup of moisture, which can turn into condensation, which pools water and eventually leads to equipment failure.

Is water protection the same as moisture protection?

No. If you allow the air around us to enter a camera, you allow water to enter in the form of water vapour. This is similar to what we see when the air in a blue sky forms clouds and then drops as rain – the only thing that has altered is the air pressure and temperature. Unless a camera can operate in 100% relative humidity (%RH) (even the UK reaches 90-95%RH in the summer) then it is almost inevitable that the camera will suffer from ingress issues. Any ALPR camera that specifies a working relative humidity less than 100% is not really offering one that is fit for purpose.

MAV Rapier cameras are IP68 and work to 100% relative humidity (100%RH).

Why is it necessary to seal a camera anyway?

For fixed cameras it is to stop the ingress of moisture which will condense inside the camera on the electronics and inside of the lenses and would lead to poor images and equipment failure. For mobile cameras it is additionally to combat driving rain/spray and the car-wash scenarios.

What is the best way to ensure removal of moisture from a leak proof camera?

At MAV, we believe that the only way to warrant our camera’s fitness for purpose is to perform a purging cycle on the cameras. This means that every Rapier camera is put onto a machine that injects dry air, sucks out the moist air in a breathing cycle that is continued for around 10-12 hours per camera. Every time the air is sucked out, the moisture content is measured and, only when the air inside has enough moisture removed do we consider it to be fit for purpose. Not only does this remove moisture from the air but also from every hydroscopic (water retaining) part within the camera e.g. PCBs for added protection.

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