Video surveillance system
Video surveillance systems are used for observation with optical-electronic devices. A main area of application for video surveillance systems is the surveillance of public or private rooms, traffic and technical systems of all kinds.
In the English-speaking world, video cameras and their installation methods are sometimes still under the old name of Closed Circuit Television (CCTV) . The term closed circuit (which can be translated as closed circuit or closed line ) refers to the fact that the images from the CCTV cameras are transmitted to a limited number of receiving devices. With the reference to the "closed line" one differentiates the CCTV transmissions from the public television, whose pictures can be viewed by a large audience.
For video surveillance systems for security applications , however, there has recently been an international series of standards that are also valid in Europe. The EN 62676 series of standards describes so-called video surveillance systems (VSS) . In Germany there is also the term video surveillance system (VÜA) .
Conventional video surveillance systems consist of at least one surveillance camera and a display monitor ; the systems optionally allow the images to be recorded (for example on video tape), and the transmission is analog, wired or wireless.
In modern systems, digital cameras that are connected to a computer via a TCP / IP network ( IP cameras ) are usually used. Special video surveillance software can be used to perform additional functions such as motion detection, face detection and data storage.
technology
Since a video surveillance system can be both a simple structure, which only consists of a single camera, the image of which is transmitted live on a single monitor, as well as a complex system with several cameras and different systems for storing and evaluating images - or video material, the technologies used are very diverse. A system can be looked after by staff from the operator or a service provider, or it can work fully automatically after installation. In fully automatic systems where z. For example, if the live image is not viewed, functional checks are carried out on a random basis and images are only accessed when required.
Initially, own, analog transmission systems were set up using coaxial cables , two-wire technology or analog fiber-optic transmission. Although this technology is still widespread, it is no longer planned in this classic form for new systems due to ongoing technical progress and the change to IP technology. This is supported by the relative unwieldiness and the wear behavior of video cassettes compared to digital storage media.
The transition to digital CCTV systems has been taking place in recent years. There are several variants of this. On the one hand there are analog cameras that are connected to a computer, which digitizes the camera signals via a corresponding card, can display them and forward them over a network. Hybrid systems of this kind are mainly found where analog cameras were already available and cannot be replaced without great effort (rewiring). On the other hand, in the exclusively digital version. IP cameras are used here , the video image of which is transmitted to the monitoring center via a private or public IP network , where it is displayed and / or recorded. The videos are transmitted purely via commercially available IT systems (routers, switches, etc.). The challenge in this case is the reliable and change-proof (i.e. legal) transmission. The change to or the integration of digital technologies therefore harbors advantages (space requirements of the storage media, image quality) as well as a number of new problems (storage and bandwidth requirements as well as the variety of formats for video compression techniques ).
In the case of digital video surveillance systems, the operator can also choose very flexibly under what circumstances and in what form (low-resolution or high-resolution image, video, possibly with sound) a recording is made. The camera itself can serve as a motion sensor; If there is movement in one or more previously defined areas, recording - or even just logging - can take place. This serves to reduce the storage requirement and the time that the operator has to invest in the inspection. The challenge at this point is to avoid false triggers due to the flight of insects and birds or even just changing lighting conditions, without missing the events that are actually to be controlled. Integration of other signal sources, e.g. B. of alarm systems is also possible.
Most camera sensors are sensitive to visible light (laser light, solar radiation, headlights). If the angle of incidence is unfavorable, this leads to overexposure of the camera image. The latter is important not only for outdoors, but also for interiors. Sunlight or artificial light falling through a window or door can significantly degrade the image of a camera. The software in cameras or in the recording system can only counteract this problem to a limited extent with white balance and individual exposure settings . The problem of dazzling a camera, which would result in completely or partially overexposed images, is often solved by setting up several cameras with different viewing angles .
Most surveillance cameras are equipped with either a CMOS or a CCD sensor, which rely on light to generate images . Nowadays there are no noticeable differences in video recordings using these different sensors, but CCD sensors are predominantly built into analog cameras, as these have a PAL resolution. The CMOS sensors are mainly found in HD cameras. Special infrared cameras are required to be able to take pictures in the dark .
Due to the wide range of possibilities for signal acquisition, processing and recording, there is no technological standard for video surveillance systems. Depending on the area and location of use, however, when selecting and installing the video surveillance system, the operators must observe country-specific legal standards and therefore limit the selection. These are also those that do not deal directly with surveillance, but with fire protection and accident prevention .
The requirements and rules for the use of video surveillance systems for security applications (VSS) are largely described in EN 62676-4 (Part 4 of the series of standards). The quality of such a video surveillance system is particularly dependent on the so-called resolution. Different resolution classes are defined for this in the standard. These also form the basis of the VdS 2366 guideline of the VdS loss prevention as well as the uniform federal guideline for attack / burglary alarm systems or systems for emergencies / dangers with connection to the police ( ÜEA guideline ), according to which images are also transmitted to the police after a hazard alarm system has been triggered can.
Resolution classes according to EN 62676-4
Monitor
Fixed functional designation of a camera to enable viewing of the number, orientation and speed of human movements over a large area, provided that the operator is aware of their presence.
One pixel forms max. 80 mm in kind.
This resolution class with 12.5 pixels per m should enable the operator to follow a group of people on the basis of a live image transmission.
From a VGA resolution and higher (also for PAL and 1080p) the minimum size of the crowd must not be less than 5% of the screen height.
Detect (capture)
Fixed functional designation of a camera to enable the operator to reliably and easily determine whether any target, such as B. a person who is present or not.
One pixel forms max. 40 mm in kind.
This resolution class with 25 pixels per m is intended to enable the operator to distinguish image changes made by a person from other influences.
From a VGA resolution and higher (also for PAL and 1080p), the minimum size of the target must not be less than 10% of the screen height.
Observe
Fixed functional determination of a camera, which enables characteristic details of individuals, such as. B. Conspicuous clothing, while viewing activity surrounding an incident.
One pixel forms max. 16 mm in kind.
This resolution class with 62.5 pixels per m is intended to enable the operator to follow an individual (e.g. a person with appropriate clothing) on the basis of a live image transmission.
For PAL resolution, the minimum size of the individual must not be less than 25% of the screen height (for 1080p: 10%).
Detect
Defined functional definition of a camera, which enables the operator to recognize an individual.
One pixel forms max. 8 mm in kind.
This class of resolution with 125 pixels per m is intended to enable the operator to distinguish an obviously known individual (e.g. a person) from other individuals.
For PAL resolution, the minimum size of the individual must not be less than 50% of the screen height (for 1080p: 20%).
Identify
Specified functional determination of a camera to enable the unambiguous identification of an individual.
One pixel forms max. 4 mm in kind.
This resolution class with 250 pixels per m should make it possible to assign a depicted individual (e.g. a person) to the original with a medium probability. In this respect, the above definition of the norm with regard to the verb “unequivocally” cannot always be fulfilled.
For PAL resolution, the minimum size of the individual must not be less than 100% of the screen height (for 1080p: 40%).
To verify
Fixed functional purpose of a camera to enable the operator to obtain information relating to an individual. An example of an individual may include text or a logo on clothing.
One pixel forms max. 1 mm in kind.
This resolution class with 1,000 pixels per m is intended to make it possible to assign depicted features (e.g. on people or items of clothing) to the original with a high probability or even a probability bordering on certainty.
For PAL resolution, the minimum size of the individual must not be less than 400% of the screen height (for 1080p: 150%).
history
The first television monitoring system was installed by Siemens in 1942 on test stand VII in Peenemünde to monitor the launch of the A4 rockets.
Applications
Public surveillance
Private individuals, companies and government institutions try to use video surveillance systems to protect their buildings and premises from attacks such as burglary , theft , vandalism and sabotage , or to be able to intervene quickly in the event of possible violations or to be able to identify the perpetrators afterwards.
In addition to conventional films and photographs, the police also use mobile surveillance cameras to monitor demonstration participants, identify them personally and document violations of demonstration requirements and laws.
The EU project INDECT , which started in 2009 and is expected to run for five years, includes massive use of video surveillance in public spaces . The aim is to detect “abnormal behavior” preventively by automatically evaluating the images from a large number of cameras. The data is shared in real time with others, e.g. B. linked to publicly available data from the Internet, for example from social networks. Suspects are then followed by fully automated flying camera drones. The project has generated massive criticism from a wide variety of sources.
Another form of public surveillance is the early detection of forest fires using thermal imaging cameras.
Industry
In space technology, television monitoring of rocket launches with subsequent recording helps to check the rocket flight and, in the event of a failure, facilitates the investigation of its causes. Cameras on the ground as well as larger missiles on board are used. For safety reasons, the refueling process is also monitored with the help of television technology before the start.
The interior of nuclear reactors is monitored with the help of television monitoring systems, since conventional viewing windows cannot be implemented or can only be implemented with difficulty for reasons of radiation protection and strength. Processes in reprocessing plants are therefore also often monitored using television technology. In addition, the use of CCTV in shipping and especially on oil drilling platforms has been established for years. The television monitoring is used for loading and unloading ships, but also for security-related monitoring z. B. used by helicopter landings and for protection against piracy .
In the chemical industry, too, the course of chemical reactions in containers is often monitored with the help of television monitoring systems. This is more convenient and safer than direct observation.
Video surveillance is also used for all experimental processes in industry and research that are dangerous for human personnel or, due to the conditions (duration, sensitivity to light, temperatures, atmosphere, etc.) under which they take place, not directly or only with massive amounts Limitations can be observed.
In England , slaughterhouses have had to be equipped with a video surveillance system since November 5, 2018.
Since these are mostly processes and situations outside the public space, which also usually take place under strictly controlled conditions anyway, this type of surveillance plays practically no role in the discussion about video surveillance .
software
- ZoneMinder - OpenSource
- Face ++ ( Megvii )
See also
To the legal aspects
literature
- Hans-Peter Büttner: Planning manual for video surveillance systems . 1st edition. TeMedia, Bonn 2011, ISBN 978-3-941350-03-8 .
- Michael Gwozdek: Lexicon of video surveillance technology: planning, advice, installation . 4th edition. Hüthig Jehle Rehm, 2007, ISBN 978-3-609-68432-1 .
- Adolf weg: video surveillance technology. CCTV manual for planners, consultants and users . 3. Edition. Hüthig, 2000, ISBN 978-3-7785-2767-2 .
- Sebastian Welzbacher: Planning a video surveillance system: common standards in analog and IP technology . 1st edition. Diplomica, 2012, ISBN 978-3-8428-7781-8 .
Web links
- IT basic protection catalogs, there: video surveillance
- Stoa report 1997 - under point 4.2 (English)
- Video surveillance in Europe Summary of the final report of a ZTG research project on video surveillance in Europe (2007; PDF file; 198 kB)
- Video surveillance using the example of London: between security madness and surveillance paranoia
- Brandon C. Welsh, David P. Farrington: Effects of Closed Circuit Television Surveillance on Crime (PDF, 76S.), Campbell Systematic Reviews, December 2, 2008, 17, The Campbell Collaboration
Individual evidence
- ↑ Chaos Computer Club ( M4V ; 124 MB)
- ↑ Temporarily Neutralize Camera Sensors
- ↑ Dirk Fisser: Greens are calling for video surveillance at slaughterhouses. In: noz.de. November 7, 2018, accessed November 7, 2018 .