Positioning Cameras in Wide Entrances and Corridors
For transit areas that are wider than a double-doorway, you need to mount several CCTV cameras in a line across the ceiling. The field of view of each camera should overlap its neighbours. Consider also the following points.
- The counting zone should be located where people are moving along the corridor: a point where people stop to talk, look at exhibits, advertising or route signposts, is not really appropriate.
- Ideally, start by temporarily fixing the cameras: you will probably need to move them after viewing the overlap of their counting zones.
- The best position for the cameras is not necessarily evenly spaced across the corridor. The cameras at the edge of the corridor may need to be closer to the edges of the wall than equidistant spacing might suggest.
- People going through the overlapping zones between adjacent cameras must be picked-up by both cameras, and be at the edge of each camera's counting zone. The VT detection units tell each other of the presence of a person at the edge of the zone they are monitoring. This means that the system handles a person being in the view of two cameras at once, and can pick up people crossing the zone diagonally.
- The cameras must be mounted in a line across the corridor spaced so that the counting zones overlap by about 10% at each end—see the figure below and the Fine-tuning Camera Placement notes.
Fine-tuning Camera Placement in Corridors
- Connect the Video output from the leftmost VT unit to a TV, so that you can see the camera image and the counting zone markers. Use the VT Setup software to adjust the counting zone edges.
- Mark the edges of the counting zone on the floor using something easily removable like masking tape. A T-shaped piece of tape to show the end and direction of the line is useful.
- Connect the output of the adjacent camera and its VT unit to the TV.
- Position the second camera so that its counting zone markers are on top of those of the first camera with an overlap of roughly a third of a metre. Use the VT Setup software to adjust the size and position of the counting zone, and set up counting through wide entrances.
- Repeat for the other cameras
- Check that someone following the walking line is detected only once.
The ends of the zone lines from the two cameras should be on top of one another, so the counting zones are level and overlapping.