Catching the action: How and when to use digital video motion detection
Catching the action: How and when to use digital video motion detection

Aug 1, 1998 12:00 PM

Define the purpose of the system to decide whether digital video motion detection is needed. The third step in understanding the application of digital technology is to consider the image itself. As discussed from the beginning, the strongest benefits of digital CCTV systems are accuracy, organization, performance and speed. Of the digital devices that deliver such benefits, digital video motion detection systems are out front. Digital video motion detection takes integration of security into the video system to new levels. Before I get too far ahead of myself, however, let's review digital versus analog and the objectives of good CCTV system design. Digital uses an advanced form of "Morse code" to produce and recreate images and commands with close-to-exact results each time. The only problem with this definition is that it gives the designer or buyer the impression that digital is an exact science. That impression is false, especially where video motion detection is concerned. Digital certainly increases accuracy and gives us the ability to analyze an image in much better detail than ever before, but it does not afford us error-proof, hassle-free video motion detection. As for objectives of CCTV system design, they should be to: - ensure that the person monitoring the system does not miss anything; - automate response and reaction to intrusion and/or compromise to protected areas. - integrate with other automated and/or static forms of security; and - ensure that evidence and visual information is recorded in proper proportions. It is important to understand that almost everyone offers one form or another of digital video motion detection built into their equipment these days, but: - not all digital video motion detection is equal or applicable in all circumstances; - two digital video motion detection-capable units cannot be assigned to the same video image; and - digital video motion detection is not the sole or necessarily even the best option for all circumstances of integration and motion detection.

Is digital video motion detection right for you? The first step to any system design is, of course, to define the purpose of the system. Use these criteria to determine whether digital video motion detection is right for your system: 1. Are you looking for an individual in an empty room or an individual in a group? As obvious as it appears, this is the number one mistake made by designers of digital video motion detection systems. Because we have the ability to monitor, highlight and even enunciate multiple points of motion within an image, many end-users and designers are under the false impression that we have the ability to pick a single person out of a crowd (with automated digital video motion detection) and follow only that person (automatically) through the crowd. Buyer be educated! A crowd is a crowd, and motion is motion, and when the two are mixed, the detection of a single, isolated point within the whole is difficult. 2. What is your capacity to forgive false alarms, and what long-term effect would such false alarms have on your personnel? False alarms are the scourge of the electronic alarm industry. They can also be the scourge of the video motion detection system. Long-term exposure to repetitive false alarms tends to slow the response time of personnel as they grow lazy. Consequently, it is important to use the highest quality equipment available for your application. To find a system that fits your application, consider a few variables. The first is environment. Do you need indoor or outdoor motion detection? Although this seems like a basic question, the answer is extremely important to the results of your digital video motion detection experience. All video motion detection is based first upon change of contrast within the video signal or image. The simpler the digital video motion detection, the simpler the style of detection. Most units that are built into cameras, multiplexers, switchers and such are based upon simple contrast change within the image. Therefore any variation of light within the coverage area, e.g., shadow over the sun, lights turning on or off, headlights sweeping an area at night, will be detected as motion. More sophisticated units give us the ability to define the amount, type, size and even the direction of the contrast change within a defined area. The size of the area and the general sensitivity to change that the unit is set for will determine what the unit sees as motion and what it sees as nuisance. In other words, the only difference between a false alarm and an actual alarm with most simpleunits is the consistency of lighting in the area of coverage. Systems that are designed to work with outside scenes are designed specifically to reduce false alarms through digital discrimination of events. Beware: Many manufacturers claim their units are designed to work in either environment. This is just not true, and there are specific differences. For one thing, if the features are "built into" a camera or multiplexer as "standard" features, the unit is not designed for outdoor discrimination. A second guideline is cost. You get what you pay for, and quality outdoor digital video motion detection costs anywhere from one to three times as much per camera as built-in motion detection. The key differences between indoor and outdoor area motion detection are lighting and the number of potential objects moving. It is not likely in an indoor situation that we would have extreme shadow motion such as a cloud passing over the sun. In addition, in most indoor applications we (hopefully) do not have a lot of stray animals, blowing debris, rain, snow, camera shake or other such offenses that require some form of intelligent discrimination. Although there are several very good digital video motion detection systems available, first, determine your goals, such as: - indoor/outdoor; - short range/wide view; - long range/narrow view; - fixed or minimally variable lighting; - heavily variable lighting; - busy scene or wide-open area. Digital video motion detection can be added easily to any existing or new video system with the installation of a unit at the main control point. Since the installation is done inside and is performed by looping the video signals through the digital video motion detection, there is little time required. One key factor here, however, is the overall quality of the video image that the motion detection is being attached to. Digital video motion detection will have problems when attached to images with a high degree of outside interference as caused by ground loops or radio frequency noise, because of the inability to discriminate between noise patterns and contrast interruptions.

What to look for Following are digital video motion detection options: - Almost all digital video motion detection units have multiple sensitivity settings. These range from simple, overall contrast change to amount of change within a predetermined area. - All units offer multiple area programming. Some give the user the ability to define the size of a target within an area, which can be useful when trying to discriminate between a forklift and a person. Obviously, since the forklift takes up more space within the detection area, it can be discriminated or not seen by the detection unit. - All units work well in close proximity to the subject. However, the test comes with the long-reach image, say a perimeter fence at 1,500 feet, because the object of detection becomes smaller. - Most units offer motion highlight capabilities. This means that the offending target is circled or highlighted on the screen for quick identification. - All outdoor units have some form of contrast discrimination built in. This is to say that an overall screen comparison to detection area can be made, and through this, determination of actual motion versus a cloud passing over the sun. Most units, however, are limited as to the type and amount of comparative filtering they do. It is a relatively expensive technology that is usually reserved for only the best outdoor units. - Some (very few) units offer motion comparison. This is also a type of filtering that helps determine if an object is real or shadow. Clouds very seldom move in multiple directions such as right to left and then back again.

- Some (very few) units offer direction comparison and settings. With this feature, the designer is given additional flexibility to program the unit to allow motion going from left to right, but trip on motion going from right to left - an important feature if you are worried about what is coming in, but not out, or vice versa. - One or two units on the market today offer tracking capability. With this feature, once a motion is detected (sa y a man walking across a field), the system is able to literally track the movement through automated pan/tilt features. It is even possible that once detected and tracked by one camera to the edge of its field, it can be handed off to the next camera in succession. - One or two units offer three-dimensional detection areas. Through the use of two or more cameras aimed at the same general scene, these units are able to create invisible, three-dimensional boxes of protection around specific areas or objects. The best advantage is a person moving between any one camera and the object does not create false alarms. You must actually enter the "invisible box" of protection. Programming of most units is usually done through on-screen menus that allow the operator to choose both the areas to be watched and the criteria or sensitivity of each. Since these units allow for open-area detection and annunciation of intrusion, the effective cost savings over conventional methods of detection is usually very good.

Where to look Indoor units are relatively inexpensive, and, as mentioned earlier, come built into many multiplexers and a few cameras. Outdoor digital video motion detection units tend to be looked at as expensive. Expensive, however, is a relative term based on need and potential loss. For indoor applications with fields of coverage of 0 to 300 feet and strong fixed lighting, you can use any of 10 or 15 manufacturer's units with acceptable to excellent results. Remember that acceptable results refer to both detection of intrusion at the desired level as well as minimal false or nuisance alarms. Some manufacturers of indoor digital video motion detection systems are: 3-Dimensional Intelligent Space (3DIZ), American Dynamics, BURLE / Phillips, Digi Spec, Detec Visions Systems, EDS-Scicon Defense Ltd., Geuterbruck, GYYR, Primary Image, Inc., Shorrock/Hymatom, Quark Digital Systems, Magal, SenStar, Tech. Services International, Vision Systems Limited. If working with outside units, the field of acceptable units narrows quickly. The cost of coverage per camera also increases. Initial setup for the first camera is always the highest since the main system must be purchased and installed. After the initial cost is covered, the per-camera costs will drop dramatically. In the end, the first camera on a good, outdoor digital video motion detection system will run between $3,500 and $5,000 (depending on the type, quality and features of the system). After the first camera, the average cost per camera should drop to between $900 and $1,800. These systems cannot be judged by cost. That is, if you are going for the low bid, you will probably get the low-bid results. Some manufacturers I would recommend for outdoor applications are (in no particular order): 3-Dimensional Intelligent Space, Magal, Geuterbruck, Primary Image and SenStar.

My recommendation of these companies is based on personal experience and extensive testing and study of the various DVMD systems as published by Sandia National Laboratories in June 1995. These companies produce systems that will produce very good to excellent results outside, in tight or wide-open areas. I also note these units to reiterate that you get what you pay for. Outdoor systems from these companies tend to cost $1,000 to $2,000 more than their nearest competitor for initial setup. But if you compare the cost of false or nuisance alarms, loss of product or security, lack of response, etc., these systems take the field, hands down, as saving a great deal of long-term investment money through accuratedetection and reporting. Remember: - The key factors to look for in outdoor applications are the extent of coverage, nuisance or false alarm filtering capabilities, and overall detection capabilities under adverse conditions. - The key differences between systems start to show up in long-range applications such as perimeter fence lines and fields.

Other options In today's market, there are several other forms of digital video motion detection being produced. Panasonic has developed a camera with built-i n video motion capabilities. Although limited, the camera actually allows the user to program (at the camera) several points within the image for movement. This programming is user-friendly and allows all the basic sensitivity adjustments. Although not acceptable for most outdoor or heavy variable light situations, it is a nice feature to have built into a camera from a small-system or covert perspective. Australia-based 3-Dimensional Intelligent Space has developed a system that works with two or more cameras viewing the same subject area from two separate perspectives. Through the inter-copulation of the images, a computer is able to determine an actual three-dimensional area to be monitored. I call this "museum coverage." It is a nice concept that allows for motion around, over and under a specific item or area without causing a false alarm. Only when the item or area of coverage is touched or entered will an alarm be announced. This is a great advancement toward providing specific coverage of items that are normally surrounded by people in motion. Also notable is Primary Image's development of a complete tracking system that allows the camera and pan/tilt to automatically stay with the subject as they move across the field of view. Digital video motion detection technology is here to stay, and it will become more readily available, tighter to specifications, and less expensive with better results than conventional electronic security methods.

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