Storage requirement for ALPR images - SharpZ3 | SharpOS 13.1

SharpZ3 Administrator Guide 13.1

series
SharpZ3 | SharpOS 13.1
revised_modified
2020-07-14

The images associated with the reads and hits are stored on disk in G64 files by an Archiver. You can estimate the disk space required to store these images if you know the average number of reads and hits processed by the ALPR Manager per day.

For every license plate read or hit processed by the ALPR Manager, the Archiver stores a set of four images:
  • One context camera image (in either high resolution or low resolution)
  • One ALPR camera image (cropped to show only the license plate)
  • One context camera thumbnail image
  • One ALPR camera thumbnail image

The size of the image set depends on the model of the Sharp camera and whether the context camera is configured to take images in high resolution or low resolution.

Use the following formula to estimate the disk space you need for the desired image retention periods.
Disk space = (ReadsPD x ImageSize x ReadIRP) + (HitsPD x ImageSize x HitIRP)
where:
ReadsPD
Average number of reads per day.
ImageSize
Estimated image size per read (depends on the Sharp model and configuration).
ReadIRP
Read image retention period (see ALPR Manager's Properties tab).
HitsPD
Average number of hits per day.
HitIRP
Hit image retention period (see ALPR Manager's Properties tab).

If your patrol vehicles are equipped with wheel imaging cameras, double the number of hits per day in your formula (there is typically one wheel image per hit).

The following table gives you the rough estimates of the image size per read based on the Sharp model and configuration.
Type of image Sharp VGA or XGA SharpV SharpZ3
High-resolution configuration      
Context camera image ~50 KB ~120 KB ~160 KB
ALPR camera image (cropped) ~3 KB ~3 KB ~2 KB
Context camera thumbnail image ~3 KB ~3 KB ~2 KB
ALPR camera thumbnail image ~1 KB ~1 KB ~1 KB
Total image size per read: ~57 KB ~127 KB ~165 KB
Low-resolution configuration      
Context camera image ~18 KB - -
ALPR camera image (cropped) ~3 KB ~3 KB -
Context camera thumbnail image ~3 KB ~3 KB -
ALPR camera thumbnail image ~1 KB ~1 KB -
Total image size per read: ~25 KB - -