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Within recent years, concerns about the public transport security have increased dramatically due to rapidly increasing terrorist activities, sexual attacks, extortion, violence, etc. The camera systems can help prevent such actions. People with criminal potential give up on these activities where they learn about the existence of camera systems. This awareness will increase the confidence of the passengers.

100% of the areas where the metro station and passengers are located must be recorded by the cameras.

PPM Calculation

By calculating PPM (pixel per meter) (number of pixels per meter), it can be determined where and at which resolution the cameras should be used. For example, the horizontal resolution of a 2MP camera is 1920x1080. In other words, it shows the image that appears on the screen with 1920 pixels horizontally and 1080 pixels vertically. If the horizontal width displayed on the screen is 192 meters when measured in meters, it is 1920 pixels/192 meters = 10 pixels/meter = 10PPM. In other words, 10 pixels correspond to 1 meter.

The table taken as a sample for the gains at different PPM values is as follows.

The viewpoints of the cameras also affect the PPM value. If the camera is facing at a very wide angle, the PPM value decreases. But the dead spot at the bottom of the camera is reduced. Likewise, if the camera is facing at a narrow angle, the dead zone distance that it cannot see at the bottom increases.

Camera height from the ground affects the dead zone distance. If the camera is installed at height, the dead zone increases, if it is installed at a lower location, the dead zone decreases.

Briefly, placing the camera at a narrow angle as much as possible affects the PPM value in a good way. Analyses function better. Hanging the cameras at the lowest point that will prevent them from being exposed to sabotage will allow us to achieve high vision quality.

The PPM value will increase as the object approaches the camera. For this reason, if the objects are going to pass in front of the camera, it may be preferable to define them here for forensic purposes. In other words, it can be foreseen to take forensic records only when the object passes in front of the camera by viewing the activity in remote areas. This allows a smaller number of cameras to be used.

Installation Recommendations

• First of all, high-resolution cameras should be used at all entries and exits. Forensic records should be able to be taken with these cameras. Persons have to be passed through door type metal detectors and/or turnstiles. In the meantime, cameras should be placed to record at least 250 PPM (definition) of each individual.
• Cameras should be placed in all narrow areas such as walking corridors and stairs to record at least 125 PPM (recognition) resolution. Ambient lighting should be at a good level.
• Cameras should be placed in the elevator halls and platform to record at least 125 PPM (recognition) resolution.
• In particular, the offices with money transfers, card loading machines, phone booths, etc. should be furnished with cameras that will allow monitoring with at least 66 PPM (general monitoring).
• The entrances of the offices and technical areas, stairwells, places where suspicious activity may occur should be furnished with cameras that will allow monitoring with at least 66 PPM (general monitoring).
• If there are dark or very dim areas, they should be illuminated or cameras with IR Led should be used in these areas.
• From all entries and exits, all passenger movement areas should be monitored in such a way that no dead spots remain. The placement of the cameras must be made in a way that allows them to be monitored with at least 66 PPM (general monitoring).
• Cameras should be placed in all vehicles. These cameras must be installed in such a way that they can be monitored with at least 66 PPM (general monitoring) at the farthest point.
• There should be available panic buttons at the critical points and cameras should be placed at these points to record at least 125 PPM (recognition) resolution. At the time of the alarm, the relevant camera should automatically appear on the screen in front of the operator.
• All security personnel should be able to login the system with smart phones/tablets, to monitor and manage the key zones more quickly, and to perform automatic monitoring during alarm, etc.
• Recording devices in both the train and the station should be in protected places. The records must not be accessible by everyone. Backup of records should only be made by senior personnel.