NPS-ANPR Technical

The NPS-ANPR consists of different programs to function and work on process flow to accomplish the vehicle numberplate detection checking and user notification.

Process flow

Motion

Images are captured and processed by a program called motion, the function of this program is to determine if there is motion in the captured images if there is a series of snapshots are taken and stored for processing by the next program -mask file processing, the program will take snapshots until the image motion threshold is below the minimum, all images will be marked by its motion event number. Events are defined as the images from the time that motion detected a change in the image, set as its threshold, until the image changes are below the set threshold.

Mask file processing

All event images are cropped to the minimum required by the set image mask file. This is to ensure the openALPR program does not need to search the whole image for the plate and only focus on the part of the image we expect the plate to be.
This dramatically increases the processing time and special care should be applied to ensure the NPS-ANPR will only search applicable areas of the image.

mySQL database

All detected plates are first added to the local mySQL database.
When the -disregard local traffic- setting is enabled on the NPS-ANPR the local database is used to determine if a plate should be sent for testing to NPS-CLOUD or not.
The disregard local traffic first check if the vehicle adhere to the NPS local traffic algorithm iaw. it checks locally if the same plate was tested in the last seven days at around the same time, this dramatically reduces the running cost of the system by not submitting the plates to be tested if found to be someone that is driving the same route daily.

Post detected plates to NPS-CLOUD

The local database is queried and if required submitted to the NPS-CLOUD servers to be displayed on the users dashboard.

Test and notifications

All plates recieved by the NPS-CLOUD servers are tested against the national NP Tracker suspect vehicle database and the users own private hotlists, if found a notification are sent to the approved users.