Capturing Better Video: Strategic Camera Placement Paired with a Standalone DVR
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Wherever there is new construction, it is likely that surveillance systems will be installed. Modern surveillance equipment is relatively inexpensive, reliable and effective for preventing crimes as well as providing visual evidence of a crime. Buildings equipped with external surveillance...
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The part of the screen shot that is circled represents the video steam from Camera #9. This camera surveys part of the south parking lot. Because 16 cameras are being monitored at one time, little detail is available from the screen shot.
Figure 4 is a full shot from Camera #9 and includes a PIP (picture-in-a-picture) of the license plate of a car. This camera has been set to “normal” regarding picture quality. Where normal picture quality is good enough for long views, the lack of resolution is not sufficient enough to zoom in on the license plate and make out any kind of detail.
To successfully capture license plates from a distance, the resolution needs to be turned up for Camera #9. In Figure 5, the PIP clearly reveals the license plate details. The camera was reset from “normal” to “superfine.”
Although this produces superior results, it also requires more storage because of the higher resolution. If all cameras are set to normal, the total amount of storage allocated per day would be 158GB (Gigabytes). If the total amount of available hard drive space is 800GB, then 5.1 days can be recorded. If all cameras are set to superfine, the size of the daily file will be 277GB. This limits the days that can be recorded on the same hard drive to 2.9.
This DVR features two internal 800GB hard drives and a CD-R reader/writer. All cameras are set to superfine (maximum resolution) as there is a passive procedure guaranteeing that all video is properly stored. Downloads are performed automatically, after hours, and are saved on a network server dedicated to data backups.
Calculating storage time
The key to determining storage time is the size of a single frame. From that, there is an equation that can be performed to determine the hard drive size or the amount of days of storage a hard drive can store.
The chart in Figure 6 is set up for a DVR that handles 16 cameras, set at “superfine” picture quality, at 7.5 Frames Per Second. The equation at the bottom of the chart can be used to determine storage for different settings.
For instance a dry cleaner might use a DVR that manages two cameras, each set for normal picture quality. Additionally the DVR will be set to be on for only 11 hours each day (8 a.m. to 7 p.m.). Using the equation: (16 x 7.5 x 60 x 60 x 11 x 2 x 1) ÷ 1048576 = 9.063 GB
(The number 1048576 represents a gigabyte of information. That is 1024 bytes x 1024 bytes = 1 gigabyte.)
Under these circumstances a 200GB hard drive would be able to store 22 days of activity.
The DVR could be programmed to rewrite the oldest data at the end of the cycle so that the last 22 days of video is always saved.
Camera placements
Well-designed surveillance plans will place exterior cameras at locations that both survey assets and cover all spaces around the building.
Blind spots are created when cameras placement allows a burglar or vandal to walk up to an area of the building unobserved, and to tamper with or disable other cameras.
In Figure 7, a building is covered by many cameras so that no blind spots are created.
Before placing cameras, it is best to devise a plan that demonstrates that all areas around the building will be covered. Coverage plans can be reviewed with the customer before installation so all questions regarding placement can be answered before installation.
In Figure 8, the coverage plan guarantees that all areas around the protected building are covered. Red dots show where cameras are placed. Green points represent doors leading into the buildings.
It is important to cover the back of the buildings. A rear window is a favorite entry point for burglars.
In Figure 9, a single camera covers the entire rear wall and windows. Cameras can be rigged so movement near the windows after a certain hour will activate the burglar alarm. To prevent false alarms by roving animals, the cameras can be configured so only certain parts of what the camera sees can apply to movement and the cameras can determine mass larger than animals.
The cameras in Figure 10 are mounted high at the top of the building. This is a great location as the area is well covered and the cameras are difficult to reach. When they need to be serviced, they can accessed via a roof hatch inside the building.
