A people counter is a device used to measure the number and direction of people traversing a certain passage or entrance per unit time. The resolution of the measurement is entirely dependent on the sophistication of the technology employed. The device is often used at the entrance of a building so that the total number of visitors can be recorded. Many different technologies are used in people counter devices, such as infrared

Infrared

Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 beams, computer vision

Computer vision

Computer vision is a field that includes methods for acquiring, processing, analysing, and understanding images and, in general, high-dimensional data from the real world in order to produce numerical or symbolic information, e.g., in the forms of decisions...

, thermal imaging and pressure-sensitive mat

Mat

A mat is a generic term for a piece of fabric or flat material, generally placed on a floor or other flat surface, and serving a range of purposes including:* providing a regular or flat surface, such as a mousepad....

s.

Retail

There are various reasons for counting people. In retail stores, counting is done as a form of intelligence-gathering. The use of people counting systems in the retail environment is necessary to calculate the conversion rate, i.e., the percentage of a store's visitors that makes purchases. This is the key performance indicator of a store's performance and is superior to traditional methods, which only take into account sales data. Together, traffic counts and conversion rates how a store arrived at sales, e.g., if year-over-year sales are down, did fewer people visit the store, or did fewer people buy? Accurate visitor counting is also useful in the process of optimizing staff shifts; Staff requirements are often directly related to density of visitor traffic and services such as cleaning and maintenance are typically done when traffic is at its lowest. More advanced People Counting technology can also be used for queue management and customer tracking. Although traffic counting is widely accepted as essential for retailers, it is estimated that less than 25% of major retailers track traffic in their stores.

Shopping mall marketing professionals rely on visitor statistics to measure their marketing. Often, shopping mall owners measure marketing effectiveness with sales, and the also use visitor statistics to scientifically measure marketing effectiveness. Marketing metrics such as CPM (Cost Per Thousand) and SSF (Shoppers per Square Foot) are performance indicators that shopping mall owners monitor to determine rent according to the total number of visitors to the mall or according to the number of visitors to each individual store in the mall.

Occupancy

For safety, public locations are often rated to hold a certain number of people. Accurate people counting is used to ensure that the building is below the safe level of occupancy. Although, no people counting system is 100% accurate and therefore must not be entirely relied upon for the purposes of health & safety, an electronic people counting system offers a relatively accurate means of managing capacity.

Non-profit organizations

Many non-profit organization

Non-profit organization

Nonprofit organization is neither a legal nor technical definition but generally refers to an organization that uses surplus revenues to achieve its goals, rather than distributing them as profit or dividends...

s use visitor counts as evidence when making applications for finance. In cases where tickets are not sold, such as in museums and libraries, counting is either automated, or staff keep a log of how many clients use different services.

Technologies

Modern people counting systems use many different technologies, each with its own advantages and disadvantages. The main types are listed below.

Tally counter

A hand-held tally-counter, sometimes called a clicker-counter, would be used; one press per person. To reset the counter, one would have to turn a knob, resetting most counters' display to "0000".

Infrared beams

The simplest form of counter is a single, horizontal infrared

Infrared

Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

 beam across an entrance which is typically linked to a small LCD

Liquid crystal display

A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....

 display unit at the side of the doorway or can also be linked to a PC or send data via wireless links and GPRS. Such a beam counts a 'tick' when the beam is broken, therefore it is normal to divide the 'ticks' by two to get visitor numbers. Dual beam units are also available from some suppliers and can provide low cost directional flow 'in' and 'out' data. Accuracy depends highly on the width of the entrance monitored and the volume of traffic.

Horizontal Beam Counters usually require a receiver or a reflector mounted opposite the unit with a typical range up to 6 metres, although range finding beam counters which do not require a reflector or receiver usually have a shorter range of around 2.5 metres.

Vertical beams are somewhat more accurate than horizontal, with accuracies of over 90% possible if the beams are very carefully placed. Typically they do not give 'in and out' information, although some directional beams do exist.

Advantages:

• Inexpensive
• Simple to fit

Disadvantages:

• Most basic beam sensors are limited to non-directional counts
• Can't discern people walking side-by-side
• Cannot count high volume, uninterrupted traffic
• High potential to become blocked by people standing in an entrance or by merchandise or displays
• Infra-red beam counters may be negatively affected when subject to direct sunlight

Computer vision

Computer vision

Computer vision

Computer vision is a field that includes methods for acquiring, processing, analysing, and understanding images and, in general, high-dimensional data from the real world in order to produce numerical or symbolic information, e.g., in the forms of decisions...

 systems typically use either a closed-circuit television camera

Closed-circuit television camera

Closed-circuit television cameras can produce images or recordings for surveillance purposes, and can be either video cameras, or digital stills cameras...

 or IP camera to feed a signal into a computer or embedded device

Embedded system

An embedded system is a computer system designed for specific control functions within a larger system. often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal...

. Some computer vision systems have been embedded directly into standard IP network cameras. This allows for distributed, cost efficient and highly scalable systems where all image processing is done on the camera using the standard built in CPU. This also dramatically reduces band width requirements as only the counting data has to be sent over the Ethernet.

Accuracy varies between systems and installations as background information needs to be digitally removed from the scene in order to recognize, track and count people. This means that CCTV based counters can be vulnerable to light level changes and shadows, which can lead to inaccurate counting. Lately, robust and adaptive algorithms has been developed that can compensate for this behavior and excellent counting accuracy can today be obtained for both outdoor and indoor counting using computer vision.

Advantages:

• High accuracy, in correct conditions sometimes over 98%
• Directional information
• Flexible in customization
• Highly scalable when embedded in IP cameras
• Integration with other systems

Disadvantages:

• Higher cost than beam systems
• May require repeat visits for calibration
• Lower lifetime and higher power consumption than thermal systems
• Many systems require PCs are not fully embedded
• Less simple implementation than beam systems
• Accuracy can be affected by differing light levels

Thermal imaging

Thermal imaging

Thermography

Infrared thermography, thermal imaging, and thermal video are examples of infrared imaging science. Thermal imaging cameras detect radiation in the infrared range of the electromagnetic spectrum and produce images of that radiation, called thermograms...

 systems use array sensors which detect heat sources, rather than using cameras as in computer vision systems. These systems are typically implemented using embedded technology and are mounted overhead for high accuracy. Because they are detecting the emitted heat from people, they are able to count in all lighting levels, and also do not need to employ complex background removal algorithms used in computer vision systems. This leads to a more stable and accurate people count.

Advantages:

• Directional information
• Not affected by differing light levels
• Can count in complete darkness
• None intrusive usually ceiling mounted
• identifiable images of people are not taken
• High accuracy, in correct conditions over 98%
• Very long lifetime - MTBF >25 years
• Highly scalable, fully embedded IP Systems
• Networkable to cover wide entrances

Disadvantages:

• Higher cost than beam systems
• Lower field of view than video systems
• Cannot be used with ceiling heights below 2.2m
• May not work in winter when people are wearing thick coats.

Synthetic intelligence

This system employs multiple IR transceivers to create a count zone at ankle height. The artificial intelligence counters function in a similar way to the human brain, in other words, each event is evaluated in terms of features to determine the correct outcome i.e. count per direction. As a person passes the count zone a pattern is generated. The onboard processor extracts the features of the pattern and based on what it has been taught makes a decision regarding the event by brute force calculation.

Advantages:

• Accuracy of 96% or higher
• Directional information
• Discriminates between human and non-human objects
• Sensors can count in outdoor environments
• Can count in all lighting conditions
• Can count in complete darkness

Disadvantages:

• Larger, more obtrusive design than other types of sensing technology.
• High potential to become blocked by people standing in an entrance or by merchandise or displays.
• Cannot count high volume, uninterrupted traffic