Plate number recognition

How to find a license plate

To be informed in real time about a license plate seen by IREX cameras:

1. Make sure the cameras tasked with finding the plate meet the system requirements.
2. Set up CarTrack Pro to recognize plate numbers.
3. Add the wanted license plate to a watchlist in the vehicle database.
4. Build an alarm monitor having:

   Cameras = those in item 1 above.
   Analytics modules = CarTrack Pro - Match.
   Lists = that in item 3 above

5. Whenever an alarm comes, verify it before taking any action that might seem like an unfounded intrusion into someone's privacy.

A post-incident investigation too may ask a question about where and when a license plate of interest was seen. Then run a by-text attribute search, where the attribute is the plate number itself, or type- and color-based search, if the plate number is unknown.

How to manage access to a parking lot

It is a typical real-time use case in which we assume there is a camera that has the entire parking lot continuously surveyed, including the entrance, parking slots, and driveways.

The vehicles waiting to be allowed to the lot need a real-time response, e.g., as the bar rises or a noticeable "Access denied" indicator turns on.

To resolve the use case:

1. Make sure the camera meets the system requirements.
2. Set up CarTrack Pro on that camera to control access to the parking lot.
3. Compile the watchlist of vehicles allowed to the lot.
4. Build an alarm monitor having:

   Camera = that it item 1 above.
   Analytics modules = CarTrack Pro - Line crossing
   Lists = that in item 3 above.

5. Switch on the Use webhooks for that monitor and configure the connection with the access control external device.

Set up plate number recognition

1. On the MAIN sub-tab in the camera settings sidebar, draw the Region of interest - the part of the frame to analyze (shown bordered in green, defaults to the full frame).




To move a vertex, point the cursor onto it and drag and drop it.
To delete a vertex, double-click it.
To add a vertex onto an edge, double-click where the vertex should be.
To move the region as a whole, place the cursor inside it and drag-and-drop.

2. On the Track, Recognize dropdown, select one of: Track vehicle, Recognize plate, Track vehicle and recognize plate or Track vehicles with a recognized plate.

The Track vehicles with a recognized plate value is required to detect forbidden vehicle maneuvers.
The detection of motorcycle rider violations requires one of: Track vehicle, Track vehicle and recognize plate, or Track vehicles with a recognized plate. 

3. Checkmark License plate is missing and set a priority to record vehicles detected without a license plate. This option is available in the Track vehicle and recognize plate and Track vehicles with a recognized plate modes.
4. Checkmark Invalid License plate and set a priority to record vehicles with unreadable or non-standard plate numbers. This option is available in the Recognize plate, Track vehicle and recognize plate, and Track vehicles with a recognized plate modes.
5. On the Region dropdown, select a regional attribution ("Europe, Asia, USA" or "Thailand") of the plate number to recognize.
6. Under EVENTS, select a priority for the "No match" events; as for the "Match ..." events, they are prioritized according to the vehicle list settings in the vehicle database.
7. Set a Threshold - the number recognition confidence limit.
8. Enter a Minimum plate size value not to recognize plates smaller in area in pixels than this value, thus enhancing the recognition score at long distances.
9. Select a Traffic density. "Average" means less than 8 vehicles in a frame at a time on average; "High" means above this. Disabled in "Vehicle tracking" mode. Repeated appearances of the same plate within this time segment are considered one event.
10. Select a Re-recognition option:

No sooner than after ... sec: Once a plate is detected in the frame, recognized, and a "Match" or "No match" event generated, the same event will continue as long as the plate stays in the ROI even if it is longer than No sooner than ... sec (diagram A below). If it leaves the ROI before No sooner than after ... sec (either the car drives out of ROI or the plate gets screened or else), the event ends up to be resumed at the next re-appearance after t = No sooner than after ... sec (diagram B); the car's reappearances before t = No sooner than after ... sec will be skipped (diagram C).




The option is recommended for monitoring over a relatively stable scene, e.g. the inner part of a parking lot, to avoid too many insignificant events generated.

After ... sec: The current event will be terminated at t = After ... sec even if it lasts longer, and new event with the same plate generated (diagram D).  In E scenario, the program behaves in the same way as with the No sooner than after ... sec option switched on in B scenario.. However, unlike diagram C, the car's reappearance in ROI before After ... sec produces a next event, and the next After ... sec countdown begins (diagram F).




The option is recommended to use whenever an event implies an active prompt response, e.g., at entrance bars or tollgates, in order to fix a possible plate recognition error, should it occur, in the next re-recognition cycle.

11. Enable the Vehicle type and color recognition to recognize vehicle type (car, bus, van, etc.) and color.

This will facilitate the by-features search for vehicle events.

12. Enable the Recognize the brand of the vehicle.

This will facilitate the by-brand search for vehicle events.

13. Enable Count people on a motorcycle, detect safety gear. 

This will facilitate the search for motorcycle riders driving without helmets or carrying more than 1 passanger.

14.  Enable the Save tracks to save the motion trajectories of vehicles for later search in the media player.
15. Define the Object focal point of a vehicle for more precise positioning of a car; this helps resolve doubtful situations e.g., when it comes to a dispute about if the stop line or a traffic separation line was crossed indeed, as schematically illustrated in the picture below, in which the "FP" stands for the "Focal point".




Select one of the available focal point locations shown in the chart below:

Set up control over access to a parking lot

1. On the camera watching the entrance to the parking lot, set up CarTrack Pro to recognize plate numbers.
2. Click the Add rule on the RULES tab to select the Line crossing on the open menu.

3. On the Line crossing card that opens, enter a custom name of the rule.


It makes sense to give a rule a self-explanatory and meaningful name since it will be the event name that the Platform users are meant to operate with. Rule names can be edited on the User Menu — Settings — Event Names screen.

4. Draw the signal line in front of the entrance bar.

The minimum distance from the line to the screen's border shouldn't be less than half of the expected vehicle size; otherwise, shift or rotate the camera.

Crossing the line will be treated as asking for permission into the lot.

5. Assign a priority rating to the "Line crossing" event. 
6. Switch on the On/Off slider .
7. Click the Apply.

Tips to review and verify license plate events

When notified about the searched vehicle spotted on a camera, click the event card on the alarm monitor to see more relevant details on the pane that opens on the right.

In the three-dot menu click:

• Search by number plate - to display all other events in which the same number plate was spotted all across the Platform instance coverage range.
• Route- to build the route of the vehicle, as spotted on the Platform cameras.

Playback an event with the media player to verify the number before taking any action to respond to the event.