Many modern CCTV installations use motion detection to record video footage onto a Digital Video Recorder (DVR). The technology is very useful reducing the amount of video images you need to record, it can be even used to alert you in real time to any potential intruders. However, as much as motion detection can be…
Many modern CCTV installations use motion detection to record video footage onto a Digital Video Recorder (DVR). The technology is very useful reducing the amount of video images you need to record, it can be even used to alert you in real time to any potential intruders. However, as much as motion detection can be a real benefit it can be a real problem if setup incorrectly. At best you’ll end up recording random video sequences which will quickly eat up your DVR storage capacity. At worst you’ll miss an intruder break into your property because the motion detection isn’t configured properly.
Setting up your motion detection camera depends on whether the motion detection software is built into the camera itself, or you are using the in built software on the DVR. As an example, many network cameras that communicate over I.P. networks have built in software to provide a variety of functions including motion detection. If you’ve bought a camera that just sends a video signal over a wired/wireless network, you’ll need to utilise the motion detection software on your DVR. The DVR itself can be a stand-alone box or a home P.C.
The easiest to configure out of all these options is the networked camera because you can access it from any P.C. on the same network. Furthermore, each camera is individually configured and self reliant (if one camera stops working it doesn’t affect the rest). A network camera can also be used to record images to a DVR and send/email images to a remote server. This means that if your DVR fails you will still get copies of your images either through email or on another remote P.C. Cameras that use the motion detection on the DVR are reliant on a single piece of software to run all cameras, if that fails then no images will be recorded. Furthermore, if the DVR itself fails then no images can be recorded.
Which ever configuration you choose the principle of setting up motion detection is generally the same. First, for each camera you’ll need to set up an area(s) in the image whereby motion is to be detected. Many interfaces use an image overlay of small squares/regions that can be selected and de-selected. Selecting a square means motion will be monitored from that image region and vice-versa. It’s important to consider which areas you select for detection. Think about the circumstances when you actually want to record images. For example, pointing your camera into a busy communal area will generate a lot of motion recordings, it’s often advisable in these circumstances to limit your motion regions to points of access to the room, i.e. doorways and windows. Outdoor cameras can often be more problematic:cameras pointing out onto the street can capture passers-by, tree’s moving in the wind can trigger detection and even rain on the lense can appear as motion. In truth, the solution to overcoming most of these problems is a combination of camera placement and motion detection configuration. Place cameras to maximise the view of important pathways and entrances that intruders will use to access your property. Minimize the number motion detection regions by selecting small areas that must be crossed to access your property.
Be aware that motion detection works by monitoring changes in image pixel light intensity, so any significant changes in light intensity in a motion detection region will trigger a motion event. This can often create unforeseen problems when the motion detector is triggered by reflections, shadows or even car headlights.
You will normally have another two main settings, one for motion sensitivity and the other for noise sensitivity. Motion sensitivity, is based upon the number of image pixels in your defined region that will trigger a motion event. It’s useful because you can prioritise the size of the object you want to detect. For example, you can detect someone entering through a door by placing a human sized region at the door opening and setting the motion sensitivity so at least half to two thirds of the region must be in motion to activate the trigger. On some cameras you’ll even have the option to define how long a motion has to be active in order to fire the trigger. Now, instead of just knowing when someone is entering a door, you can monitor if someone is waiting outside your front door, effectively creating a front door bell.
The noise sensitivity is there to filter out any noise in the image and is based upon the signal to noise ratio of the camera.The signal to noise ratio is the ratio between the strength of the camera signal and the noise present in that signal. This varies between cameras, but is more important in low lighting conditions when the camera amplifies the weak camera signal. In this case the ratio of noise present in the signal is increased, seen as white fuzzy noise in the camera image. Why is this important to motion detection? Well, because motion is detected by the number of changing pixel intensities in a given region and that also includes noise. If you have a lot of noise in the image, this will effect the performance of your motion detector and you’ll need to adjust the noise sensitivity accordingly. For this reason, it’s important to calibrate your camera both in daylight and night time conditions. Many cameras will allow you to have separate settings for low light conditions. If you need your camera to work in very low light, then either you need a camera with a low light lux rating, or use an infra-red camera.
Although setting up motion detection on your CCTV system may seem time consuming, it can have a huge effect on the performance of your system. If done properly, you will be able to monitor the daily activity in and around the home without the inconvenience of trawling through endless empty images!