Static video cameras
Description/objectives
Static video camera systems can be divided into two main categories, digital and analogue systems. Static refers to cameras which are fixed in one position and can viewed but not controlled remotely. The most commonly implemented technologies for each of these categories are digital IP (Internet Protocol) camera systems and analogue CCTV (Closed Circuit Television) camera systems. Static video surveillance systems allow service operators to monitor activity in vehicles or at stations across the whole network remotely. These systems are designed to provide additional passenger safety, a deterrent for criminals or vandals, and evidence in insurance claims or court actions.
While sometimes considered old technology, CCTV camera systems are still widely utilised for surveillance purposes. CCTV cameras provide analogue video which is transmitted via coaxial cable to one particular location where video is recorded and monitored. A group of networked cameras can be viewed from a monitoring station where multiple camera video feeds can be viewed on a single monitor. CCTV footage can be recorded in analogue format using a VCR (Video Cassette Recorder) or in digital format using a DVR (Digital Video Recorder). Analogue video requires larger storage capacity than digital, cassettes can deteriorate over time with repeated use and analogue video does not provide as many analytical capabilities as digital. The DVR unit converts analogue video into a digital format, compresses it and records this converted and compressed video. This provides the additional function of allowing CCTV footage to be remotely viewed from a number of locations simultaneously. An important consideration in using a DVR system is the compression of the video in the recording process. Different systems perform this function to different degrees, and as such operators must ensure that the resolution is not compressed to an unusable level, but does not remain so large that it is difficult to store or transmit. Another important consideration is that analogue CCTV system require wiring between the cameras and the VCR or DVR unit which is usually located at a monitoring station. This can means difficult installation and limits the distance at which cameras can be positioned from the monitoring station. IP cameras are advantageous here because they process footage internally and transmit this via wireless internet connection. These cameras are also capable of storing footage so that if signal failure occurs there are no losses. Due to this, IP cameras can be viewed from any location globally provided there is an internet connection available.
Analogue CCTV systems are lower cost than IP systems but require expensive cabling and provide a lower level of analytical capabilities. Additionally, these systems usually provide lower quality footage than IP systems with lower resolution and fewer frames per second, typically 10 frames per second as opposed to an average of around 30 frames per second or more for IP. Analogue CCTV systems can be installed on vehicles but require connection to a mobile recorder unit which is installed on the vehicle. This unit is generally a DVR which can be connected to the on-board computer system to facilitate data transmission using the vehicle wireless radio systems, usually via wireless LAN. Alternatively the recorder unit can use its own embedded wireless devices and act as a stand-alone system. CCTV/DVR systems can also include an embedded GPS card, or a connection to the vehicle AVL system, which allows vehicles to be tracked in line with video footage.
IP camera systems provide varying degrees of high quality video depending on the system, with some being able to offer high definition quality. One difference between analogue and digital systems is related to the processing and transmission of footage. In digital IP systems images are processed in the camera prior to transmission, whereas analogue cameras transmit unprocessed video to the DVR or VCR unit. IP cameras can internally record images or this can done via connection to a Network Video Recorder (NVR). Data transmission to a central computer or monitoring station can occur through a single Ethernet cable, which can also be used to provide power, or cameras can have an embedded streaming server to transmit images wirelessly over the internet, with a separate power connection. In mobile applications data transfer occurs in a similar way to that of CCTV/DVR systems, via embedded or in-vehicle wireless devices. Embedded GPS or connection to the on-board AVL system is also possible. Both systems when applied to mobile situations can be tailored to provide near real-time footage. However this may not be reliable due to signal problems. If video is transferred using a publicly accessible wireless network there may not be sufficient continuous signal or bandwidth to accommodate video transfer. This is because open mobile networks there is competition for service and only a best effort service can be provided. As such it may be better to use a private wireless system such as a TETRA digital private mobile radio (PMR) network with a guaranteed level of continuous bandwidth, or to avoid real-time video monitoring and to solely use an opportunistic download based wireless LAN network.
Applications
- Surveillance
- Operations management
Benefits and cautions
IP cameras require a high bandwidth for data transfer and in mobile applications this makes these systems more susceptible to interruptions in real-time streaming of video when publicly accessible wireless systems are used. As such there may be a need for a trade-off in image resolution to reduce the bandwidth requirement. The level to which video is compressed for transmission or storage is also a very important consideration though, and a balance must be achieved between maintaining a usable quality of footage and compressing the images enough so that the bandwidth requirement is not too high.
While currently more expensive than CCTV in terms of initial price, IP systems are becoming more cost competitive and for larger scale systems IP may already be more cost-effective. However, the additional maintenance costs over time needs consideration, as complex IP systems require skilled IT management. While potentially more expensive in the long-run due to this additional maintenance, IP systems do provide greater functionality, allowing for a greater level of video analysis as well as remote wireless access on any internet connected device.
In terms of real-time data transfer from vehicles, when investment is available a PMR (private mobile radio) network is preferable as it removes signal and bandwidth availability problems, in addition to potential hacking threats. This is an expensive solution though due to the necessity for adequate base station coverage over the entire network. As such it may be better to avoid real-time monitoring until more developed publically accessible mobile data transfer systems can offer flawless service provision. Fundamentally there is also a certain amount of debate regarding the actual effectiveness of video surveillance systems in terms of crime prevention, as well as the invasion of passenger privacy. However, the video evidence potential for operators in terms of liability actions or other court cases reduces the importance of the effectiveness debate. This is especially true when external vehicle cameras are used which can help to determine liability in road accidents.
Relevant case studies
Dublin, Florence, Zurich