What to know about the different motion detection methods
Source: William Pao, a&s International
In security, motion detection
is of utmost importance. There are different motion detection technologies out there, and choosing the right one really depends on the user scenario.
That’s according to a blogpost
by Axis Communications, which summarizes different types and motion detection technologies and their pros and cons as follows.
According to the post, passive infrared (PIR) sensors pick up heat signatures from objects within their field of view. Drawbacks include it doesn’t have the greatest range and can easily pick up objects such as spider webs and leaves, thus triggering false alarms.
However, PIR sensors have strengths as well. “They work well in smaller indoor areas and don’t ‘see’ through windows – a problem sometimes encountered by video motion detection. And, given that they have been used in security systems for so long, they are also fairly affordable,” the post said.
Video motion detection (VMD)
VMD combines the images generated by a security camera
, with software that can analyze the images as they are captured. “This method of motion detection relies heavily on two key components: the quality of the image from the camera and the quality of the analytics software in use,” the post said.
In terms of pros and cons, the post points out: “The camera is blind if there is not enough light, and open to blinding if there is too much backlighting. On the upside, video is a widely implemented security solution and adding a layer of analytics is fairly cost-effective.”
According to the post, thermal cameras
are not really cameras in that they don’t pick up visible light. “To oversimplify, they are sensors that create an image based on temperature differences between objects in their ‘field of vision,’” it said.
Thermal cameras are effective, they do come with a price, literally, the post said. “They have an excellent range even if they do focus on a fairly narrow area; they can pick up heat signatures through smoke and fog and are immune to many conditions that would be problematic to visible light cameras – shadows, darkness, backlight and even camouflaged objects,” it said. “Whilst these thermal imaging cameras are highly effective, they do come with a similarly high price tag which can put the technology out of bounds in many cases.”
works by transmitting radio waves and receiving the same waves bounced off objects in its field of detection, and can calculates distance, velocity and size of objects in relation to the detector, the post said.
Benefits are manifold. “Radio waves pass through unsubstantial objects such as spider webs, leaves and smoke, allowing radar equipment to focus on objects of significance,” it said. “In addition, it can detect motion across a far wider area than thermal cameras even if it does so over a shorter range. Radar comes in at a price well below that of thermal cameras and not far off PIR sensors.”
In the end, the user should choose a technology depending on their user scenario and budget, and how well the technology fits into the user’s existing system.
“([The end user] should choose a solution that fits the specific job. Every installation will come with its own challenges – be they budget constraints or challenging conditions – and each will require a tailored solution to meet the requirements,” the post said. “Security systems are at their most effective when made up of a collection of best-in-breed components working seamlessly together. So, before deciding on a new component for your system, ask yourself how it will fit into your existing network and whether it will work with components you might want to add in the future.”