Counting People FAQ

Video Turnstile
People Counting Systems from Biodata Ltd

Video Turnstile Counting People FAQ

  1. What are the height limitations for mounting the camera?
  2. What is the maximum counting rate?
  3. How do background lighting changes affect the detector?
  4. What is the output format from the software?
  5. Can Video Turnstile monitor busy places like underground stations?
  6. Can Video Turnstile count vehicles?
  7. Are children counted?
  8. Is it easy to install?
  9. What is the pulse specification from the VT unit, if I wish to connect the Video Turnstile detector up to my own logging system?
  10. Is it DSP based?
What are the height limitations for mounting the camera?
The CCTV cameras normally used are supplied with a standard 3.6 mm lens and are suited for installation between 2 and 3 meters above the floor. If you need to mount them higher than 3 meters a different lens is required to restore the video picture to the parameters used by the detector.
What is the maximum counting rate?
The detector is designed to count people going through a zone about the size of a double dooorway. It will count two people crossing together either in the same direction or in opposite directions. There is a minimum time between people of 0.3 seconds. In normal circumstances a double doorway will limit the number of people transitting to around 5 per second.
How do background lighting changes affect the detector?
The detector continuously monitors background light level and responds to changes in lighting (for example lights being turned on and direct sunlight changes over a period of 1-2 seconds). The detector will also respond to changes by the camera to its white balance caused by people making a substantial change to the amount of white in the video picture.
What is the output format from the software?
The VT Collect program is used to collect data from the Video Turnstile loggers at regular intervals - e.g. hourly. It produces a text data files with a table of counts by time. The table contains tab separated values with columns which represent count inputs (e.g. door1_in, door1_out, door2_in, door2_out etc). The first column is the time of day for the count. Data files will normally be daily files, for examples see the Software page. The files can be imported into most Windows analysis and reporting software. Biodata themselves do not provide report software, and are happy to cooperate with resellers who wish to add their own value to the product in specific application areas.
Can Video Turnstile monitor busy places like underground stations?
In principle you can set up a people counting system for a train station. We have previously done this with infrared sensors, which work reasonably well, and we expect Video Turnstile to perform better. However, there are a number of considerations:
  1. VT units would need to be placed above a zone where people transit, for example a passageway to the trains.
  2. You couldn't place a unit near where people are queuing or waiting (so not close to the ticket office or displays for train arrivals and departures).
  3. We would need to know the height above the floor, because the standard cameras are set-up for floor to camera height of 2-3m. For greater distances a different lens would need to be selected. Also we would need to know the width of the passageway being monitored to estimate the number of VT units required.
  4. The system should not be subject to sudden changes of light levels when counting many people, so the platform of an underground station may not be appropriate.
  5. We would recommend a trial first, to assess count accuracy and suitability of placement.
Can Video Turnstile count vehicles?
This would require a firmware change to Video Turnstile detector units, but at Biodata we have not yet tried this. A situation where the camera is above the roadway, for example a bridge or entrance to a parking area, would be appropriate.
Are children counted?
Whether or not children are counted depends on their size. You can set the thresholds according to whether you want small children to be counted or not.
Is it easy to install?
Any competent electrician will be able to install the people counters. They normally work without adjustment, but can easily be tuned to specific requirements by switches on the back of the units. Installation is clearly explained in the User Manual supplied with each system.
What is the pulse specification from the VT unit, if I wish to connect the Video Turnstile detector up to my own logging system?
The pulses that are output through pins 7 and 19 of the 25-way D-type connector on the front of the Video Turnstile units. They have the following specification:
Signal:    Normally high (12V DC) pulsing to ground
Duration:  For Up screen pulses:   100 milliseconds
           For Down screen pulses: 200 milliseconds
An adapter unit is also available that makes these pulses available as two volt-free contacts - please contact Biodata Ltd for more details if this is appropriate to your system.
Is it DSP based?
It is not based on a digital signal processor chip, although the processing is done by firmware in a logic array within the Video Turnstile detection unit. The logic array produces count pulses for the Up (screen) and Down (screen) transits of the detection zone. Within a logging unit these are passed direct to the logger, while for detection units only they are passed by a connection cable to the logger. The count pulses can also be connected via a cable to the Display Meter.

Request a Quote for a Counting People System

To request quote for a counting people system, or to discuss your application, please fill in our on-line questionnaire.