Criteria editing box of license plate reading area

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Criteria editing box of license plate reading area

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Criteria editing box of license plate reading area

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Graphics window

Main menu


License plate reading area

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These criteria are the following:


Minimal height of license plate reading;
Maximal height of license plate reading;
Minimal vertical size of license plate image (pixel);
Maximal angle between a direction on the camera and horizontal.


A license plate height is taken as equal to 0,1m (0,33 ft).


In multi-level 3D projects the heights in the criteria are calculated relative the Base height of the camera, for which the person detection, identification, license plate reading areas are calculated.



The criterion Minimal vertical size of license plate image (pixel) depends on vertical number of pixels. Vertical number of pixels influences person detection, identification and license plate reading areas.

For criteria calculation minimal number of pixels from parameters of camera image sensor and parameters of output image is used.

Number of pixels of image sensor is specified on the Sensitivity and Resolution box.

Number of pixels of output image is specified on the Processing tab of the Image parameter panel.

If a camera is rotated by an angle more than 45 degrees, when calculating person detection and identification, license plate reading areas,  the parameters: minimum vertical resolution (pixel/meter, pixel/ft), the minimum vertical size of face image ( pixels ), the minimum vertical size of license plate ( pix) are calculated based on the number of pixels along the horizontal, instead of the number of pixels along the vertical, as in this case the vertical side of the field of view is located along the horizontal.

In other respects the license plate reading area doesn't take into account rotation of camera around its axis, shadows and lens distortion.


If number of pixels is not set (N/A), calculation is performed for vertical 720 pixels (1280 on horizontal).


Since the license plate is a flat object, the angle included between an optical axis of camera lens passing through a license plate and a horizontal has a smaller value comparing to a license plate reading procedure. It is to be kept in mind though that with the angle large values the sensitivity to a vertical skew of license plate ascends.


The license plate reading projection is calculated on a condition of license plate hitting in the area at all the heights from the customized range. For instance, to read the license plates of the passenger cars out only, the maximal height parameter is to be changed. In this case the calculated license plate area extends.


The box upper part contains a quality level combo box enabling to choose any quality level. The criteria values relevant to the chosen level of quality are immediately displayed in the box. The criteria values can be edited, by typing the new values. If the edited quality level coincides with the quality level of the active camera, all the criteria alterations are immediately taken into account when calculating the license plate reading area.


To save the introduced changes click OK.

To cancel the introduced changes click Cancel.

You can set your own criteria using the 3D Video as a control monitor and moving 3D models in the camera view area.


You can change the criteria values of several quality levels outright. Clicking OK saves all the introduced changes.


See also: Recommendations on the program use, Pixel density box.

External link: "The principles of CCTV design in VideoCAD. Part 2. Person detection area, person identification area, license plate reading area. Pixel density."(*.pdf) .