Camera in outdoor car parks catch heaps of action but are typically – well – useless for evidence.
Their intent is typically used to observe behavior and be a visual deterrent. Activities of interest include vandalism, loitering, theft, assault and carpark misuse but in reality, for most installations I have reviewed, you would have more change tracking an individual ant through the mowed grass.
The ability to recognize a person from a camera covering a perimeter wall or carpark area is not always possible and as such is often ineffective as review tool or for evidence. This is due to the combination of the cameras installation height and scene width.
For example
In this clip you can see a huge amount of the car park. Maybe 100 cars when it is full but only the lower third of the scene is possibly useable. I say possibly because the camera is too high to see a persons face, too low a resolution to read a number plate and depending on which way is west, will be blinded by the afternoon sun.
The best practice to CCTV in a car park is to have several higher resolution cameras, which are covering the key points around the perimeter where most pedestrian and vehicle traffic passes.
These cameras provide the ability to recognize a person or read a number plate and when combined with the typical overview cameras provide an evidence chain of who the person is and what they did.
This has proven in practice to provide a level of coverage that is not too demanding on the recording storage but still provides the detail the police require for evidence.
Sufficient detail is also provided for video analytics such as cars parked too long, allowing you to better manage your parking spaces and suspicious out of hours behavior to alert the remote video monitoring so they can observe and react.
The following illustration shows how we would co ver a typical shopping centre with cameras placed to give in image suitable to recognize someone in the yellow zones and observe behaviors in the green zones.
First we provide a reasonable level of coverage at key choke points to obtain an image quality suitable to read a number plate or recognize a person. This is using the higher resolution 4K cameras which allow recognition quality at greater distances into the scene. We could use these 4K CCTV cameras for the entire site however this would significantly increase the storage requirements and overall system cost.
The top of the camera scene SHOULD NOT include the horizon as many installations I see do. All this does is records unimportant information and causes backlight problems when the sun is on the horizon. Instead have the end of the camera scene about 1 metre above the furthest point on your property.
In the scene below, apart from a beautiful sunset, what else are we going to gain from the top third of the scene? UFO’s?
Getting 95% Coverage
Combining this with several cameras designed to give and overview (wider scenes but less detail) and 720p resolution allows us to track a person or vehicles movements around a carpark with a 95% coverage after initially detecting them with a camera of recognise quality.
The result is that for much of the car park, we will be able to track a person with enough detail to know where they walked and with the higher resolution cameras be able to recognise them.
While there are some car park layouts that this will not be effective in, the results will be significantly more useful as evidence than the traditional coverage.
Other considerations are the type of camera housing, the mounting height and the growth of trees in the scene. Car park cameras have a habit of either getting knocked off the wall by trucks or being stolen. To avoid this use vandal resistant domes where the lens focal length is sufficient. Mounting them higher will also help with this problem but will increase the likelihood of not seeing a face underneath a hat as well as increasing the cost to service the cameras with the requirement of elevated work platforms.
The tree issue is just something you need to plan for and allow in your budget to prune the trees or move the cameras as required.
What is your experience in car park surveillance? Any tips that might help others?
