Coverage

The process which begins in Survision camera and ends in a real-time recognition of a license plate number from a video stream follows 4 main steps (in less than 20 milliseconds):

1. Localization of the License Plate: The role of this step is to identify the license plate within the image. This allows the LPR engine to focus on the plate and disregard any extraneous data in the picture.
2. Segmentation of the plate: The role of this step is to identify the precise zone containing the characters and to separate each individual letter or number.
3. Character identification: The role of this step is to recognize the individual characters previously identified.
4. Syntactical correction: The role of this step is to identify, by applying regionally syntactical rules, the ambiguities concerning characters which appear virtually identical (I and 1, O and 0, B and 8, …).

At every stage of the recognition process, Survision R&D uses several different image processing algorithms, as well as Artificial Intelligence. It is naturally during the steps of character identification and syntactical correction that the integration by SURVISION engineers of special features of each type of plate is the most critical. It is during these two stages that the specific characteristics of each country are identified and compared to the most deterministic models, depending on what we called “Country/ State Context”.

Using the VSS Tool provided by Survision, the Installer choses the country in which the camera is installed. The existing syntaxes in this country are then loaded. Only the syntaxes of this country are considered in the recognition process.

Yes, it is also possible to activate the recognition of plates of countries of the same continent as the selected context. To do this, the syntax “OTHERS” must be added to the initially selected country. All the syntaxes of the same continent are then loaded and organized into a hierarchy according to an internal algorithm which depends on the initial localization.

The plates of the selected country will therefore have a higher hierarchical level than the plates of bordering countries, which are regarded as having greater importance than the plates belonging to countries of the rest of the continent. 

For example: if we add « F>OTHERS » to the context string, all plates will be read but, in case of ambiguities between France and another country the French syntaxes will have a higher hierarchical level than the syntaxes of bordering countries, i.e. Belgium, Germany, Luxembourg, Switzerland, Italy, Spain and England. These will have a higher priority level than the plates of the countries of the rest of the European context. This organization into a hierarchy is useful to identify potential ambiguities appearing during the recognition process.

There are 3 possible Country Integration Status:

1. NOT INTEGRATED: if a country/state does not appear on the list below, it has not been integrated by Survision. Our R&D Team is working everyday adding new countries, please contact us if your country/state is not present on the list.
2. PRE-INTEGRATED: Survision R&D Engineers have recorded videos in that specific country and have integrated the syntaxes in the firmware, but there are not yet enough significant installation on that country/state to validate the Integration definitively.
3. INTEGRATED: Survision R&D Engineers integrated the Context syntaxes and Survision cameras have already been installed and successfully tested on several projects in that country/state.

License Plates in a given area often change. New syntaxes are added. Old one are retrieved. New formats are sometimes adopted etc.

If these changes are not integrated into the camera’s firmware, the performances will rapidly decrease.

The integration of a new plate consists of:

• Determining the optical protocol which gives the best contrast on the plates concerned by day or by night.
• Recording videos according to all possible situations (day, night, different types of vehicle etc.).
• Integrating graphical characteristics of characters and of the actual plates.
• Integrating the syntaxes.
• Testing the new developments in a real situation.

The Integration process can vary significantly depending on the context.

A syntax can be added to a country in a matter of hours or days if it obeys the same rules as the previous ones and does not involve modification of optical characters. 

The addition of plates of a new country/state presenting new optical characteristics and complicated syntactical rules may take up several months.

SURVISION has a unique firmware which integrates all countries and syntaxes. As a result, evolutions on the integration of number plates are made available by updating the firmware of already installed cameras. SURVISION provides updates of its firmware 2-3 times a year and the precise nature of the evolutions is provided in a “release note”.

The update can be done one camera at a time or by using a mass updating tool provided by SURVISION (SUT). If there is an evolution of plates or syntaxes, it is essential to update in order to maintain good performance of cameras without delay.

The updates can be carried out in the framework of contracts which provide for evaluative maintenance of the cameras. SURVISION strongly recommends at the start of the project that this type of contract is put into place. Otherwise, the integrators are informed of new developments and can request an update quotation and decide whether to apply them to the existing camera pool.