printer friendly version

The difference between indoor and outdoor VMDs

Indoor and outdoor VMDs are very different. This is according to Sian Jenkins of Primary Image.

"Each type of VMD has a unique environment to perform in and, whilst some systems claim to be suitable for use either inside or out, no system will perform well in both situations", he explains. "Choosing the right type of VMD is crucial. VMDs designed for indoor use are inexpensive and plentiful. VMDs designed for outdoor use need a greater list of features, which is reflected in the price. As is the case with most things, you get what you pay for and the difference is marked."

Features available on outdoor VMDs include 'zone masking', which limits the size of the camera scene by blocking certain areas of the screen from detection. "In principle this is a good idea", explains Jenkins, "for a site with a detection area edging onto a busy road, regular traffic could cause so many false alarms as to render motion detection impossible. But, masking one particular area means it's impossible to use a PTZ camera, because the mask will move too, and may obscure an area you want to detect in."

According to Jenkins a good outdoor VMD will offer zone masking as an option and will ignore certain movements such as blowing trees, running water and light changes. Sophisticated systems can even indicate if a camera has been covered over or dazzled by bright light by triggering an alarm.

The VideoTracker video motion detector from Primary Image

Today, some cameras, recording systems and multiplexers boast built in video motion detection. However, Jenkins warns that one needs to be careful as not only is this likely to be of a very basic kind, it is also likely to false alarm on the slightest light variation and have little sensitivity control. "Built-in VMDs may also affect performance of the equipment it is supplied in - some recording systems can only detect activity by slowing primary processes down considerably. If considering a built-in VMD, be sure to test it in the environment it is to be used in, and compare performance against a freestanding VMD. You will see the difference", Jenkins concludes.

For details contact Sian Jenkins, Primary Image, (0944) 8700 788 888.

Share this article:

Further reading: