Video Security System (VSS) Design Guide
This guide has been developed to assist
customers with those decisions that are needed to successfully plan a video
security system. The guide does not pretend
to be comprehensive, but rather, the goal is to provide a tool that initiates a
fruitful conversation between the customer and the professional.
Professional vs. Improvised Project
A Video Security System can be implemented in
two ways. One can either hire a
professional to do the job, or one can proceed “do-it-yourself”. Kits are available at your local discount
store or on-line from eBay. These kits
have improved in recent years, and it is now possible to find a kit with good
quality components, but you have less control since it is a package deal. Before you make your choice, it is
recommended that you contact the manufacturer to get an installation price quote. This will prevent surprises later. Even if you plan to do all the work yourself,
you can reverse engineer the price quote from the manufacturer to estimate
hidden material requirements, and better understand the total time and effort that
will be required.
If you decide to hire a professional, they
will assist you in selecting the components for your system. It is important to hire a qualified company
for this work. In many states, licensing
insures that companies are technically qualified, are criminal background
checked (including drug tests), and have insurance. Licensing is mandatory in some states (like
Cameras
Most
people try to monitor their property with as few cameras as possible to save
money, both in hardware costs and installation.
However, one should balance this goal with the need to capture necessary
detail. A few cameras configured with
wide views will be complemented with other cameras monitoring critical points,
for example, entrances with narrower
views (and more detail).
Video security has changed dramatically in
recent years. The events of 9/11 have
led to dramatic improvements in the technology.
Coupled with the growth of computer technologies, the industry, once
dominated by “burglar alarm” companies, is increasingly supported by the IT
professional.
The number of cameras will directly affect the
attributes of the video management system.
The design of video security systems is usually based on monitoring key
assets and chokepoints, for example building entrances.
Chokepoints are an efficient method of documenting
the movement of individuals.
Chokepoints can include hallways, parking lot driveways, and entrances
to common areas.
Key assets include items that are both of
significant value, and are subject to abuse.
For example, one customer used a manufacturing process for their
production that used a platinum “target” that weighed several pounds. The machine that used this component, as well
as the storage of spare components was monitored by their video security
system. Even though the component was
worth more than a year’s wages for most of the workers, the monitoring system
kept honest people honest.
The number of cameras will directly affect the
video management plan. For these
purposes, it is better to “pad” the estimate, as it is normal for new needs to
evolve.
Camera Technologies
Conventional vs. Infrared
(IR): The night-vision
(IR) camera is currently very fashionable.
Countless packages from the manufacturers include a set of IR
cameras. There are applications that are
best solved with this technology, but it is currently a common mistake for the
IR camera to be used indiscriminately.
Many IR cameras have a range of only 50-60 feet in night-vision mode. The range is proportionate to the amount of
IR illumination provided by the camera, usually with IR LEDs (more information on night-vision). If your field of view has a light equal to a
cloudless full-moon night, a conventional camera with auto-iris functionality
can offer superior performance.
Fixed vs.
IP vs. Analog:
Most modern video security systems are now digital. The difference with the IP camera is that the
video signal is digitized within the camera.
This makes it possible to interface with the camera with
Lens:
The first decision is whether to use a manual iris or an automatic iris
lens. If the camera is indoors with
constant lighting, a manual iris is fine (and less expensive); otherwise an
automatic iris is strongly recommended. Outdoor
lighting intensity can typically vary by a factor of 10,000. Focal length is the other important lens
decision. As the focal length gets
smaller, the field of view increases, but makes for a more distant view. Adjustable focal length lens can be
varied.
The
selection of cameras is critical to the success of your project. Everything else in the project can be done
well, but with the wrong cameras, it is a wasted effort.
Reference: Lens Size vs. Field of View
Video
Management System
Video management systems are the logical
center of the video surveillance system, receiving data from the cameras,
storing the video, and interfacing with the rest of your information
system. At installation, this system’s
importance will not be obvious, but as you utilize the system, this module will
become very familiar.
All modern video management systems have at
their core a computer. Some systems use
a generic P.C. with video acquisition hardware added. This is usually the cheapest and most
versatile option, but is also the most maintenance intensive, and least
reliable.
The other option is a digital video
recorder (DVR), which indeed includes a computer, but the computer is not a
generic P.C., but is instead is an embedded computer with hardware and software
designed specifically for the job of managing a video security system. A DVR is unlikely to be compromised by a
computer virus, or conflict with other installed software. Most modern DVR systems support Internet
protocol, which means that the system can be connected and share video with the
organization’s information network.
If you choose a DVR, the software will be
bundled with the hardware, and the software attributes should be a prime
consideration in the selection. If you
choose to utilize a P.C. as the host of your video management system, then the
software used to process the video should be chosen carefully. It is important to understand how your system
will be utilized. The most common use of
surveillance video is for historical investigation. Well designed software can prove invaluable
during this work.
The use of computer software to identify
possible important events is called Video Analytics. At large airports and other venues,
sophisticated software looks for suspicious behavior, such as the abandonment
of a package, or even someone unusually nervous. A more common (and less complex) application
for the average user is motion detection (more information on video
motion detection). With a
motion detection log, the review of video of a normally quiet environment can
be performed much more quickly (more information on video
analytics).
Video data storage design is an important
decision. Video storage will account for
a significant portion of total system cost.
The software used for the storage will allow the efficiency of the
storage to be increased dramatically. MPEG-4
(and a subset of MPEG-4, H.264) is the most common algorithm used (more information on video compression). A single camera can consume 7 GB of storage
per day. Most organizations store 30-60
days of video. If the system has 10
cameras, 60 days of storage could account for more than 4 terabyte of memory
consumed (more information on video storage).
Reference
·
Motion Detection Video Security
·
Do Surveillance Cameras Reduce Crime?
·
New Technology for Security Cameras