What Are the Main Types of Surveillance?


Surveillance is done covertly, enabling human intelligence operators to gain unbiased information about an individual, group, or organization without their knowledge. It can be done by observing a target from a fixed location or via remote technology, such as CCTV.


Observation is the most common type of surveillance and involves watching a person or a place. It can be covert or overt. Examples include police observing criminal activity in their jurisdiction, private investigators spying on celebrities and politicians, and the military using radar and satellite tracking devices to monitor battlefields. Other types of observation are economic (like credit card purchases), social (via Facebook and email), and postal (via the postal service and online).

During human surveillance, agents may interview people to gain information on an individual’s activities. This is especially important in a missing persons investigation where the subject’s family, friends, and associates are interviewed to get more insight into their whereabouts. Interviews can be conducted over the phone, in person, or via video conference.

Physical surveillance includes using hidden cameras and recording equipment placed in a vehicle, such as a car or a boat, to observe a subject’s movements around the area. This type of surveillance is often used to track a specific individual for various reasons, including monitoring VIPs and close personal protection clients who need to be monitored on a regular basis. Discretion is key in these situations, so the surveillance team needs to be able to operate without being detected.

Other forms of surveillance can be very technical and include the official or unofficial tapping of telephone lines, the interception of mail, and the use of listening bugs. Using these devices allows a monitoring agency to listen in on conversations, identify a target’s voice and location, and even transcribe speech through text-to-speech software.

Another form of passive surveillance is the sentinel influenza surveillance system that sends a healthcare worker to collect nasopharyngeal swabs from patients at designated sites. This is a very time-consuming method of surveillance, but it can provide more detailed disease data than if health authorities only collected the same types of data from all reporting healthcare workers. This surveillance method requires healthcare workers to be incentivized to participate in the program. Passive surveillance is a very effective tool during epidemics but is not very useful in slow-moving diseases such as the common cold or seasonal flu.


A video surveillance system uses cameras to record images of the area being watched. The images are transmitted to a monitoring center, where the data is analyzed and stored. This method of surveillance is used by law enforcement agencies, security firms, and even private citizens.

A covert form of surveillance is when an investigator follows a person but does not remain visible to the subject being observed. This is often used in insurance or spousal investigations. It is also employed by security firms, large and small, to track criminal activity in a business or public area.

Physical surveillance may include bodyguard services, where an operative follows a high-profile client in order to protect them and their family members from potential threats. This kind of surveillance can also be used for other reasons, such as securing an office building for a business or monitoring the movements of an individual in order to provide them with personal protection.

Covert surveillance devices, such as listening bugs or GPS tracking devices, are sometimes used to monitor a person’s movements without them knowing about it. These devices can be hidden on a person’s vehicle or their body and transmit data back to the receiving party.

The most comprehensive epidemiological surveillance is often used at special events like the Olympics, Superbowl, or political conventions. It is labor intensive and expensive, however, and requires additional staff to collect symptomatic information from many people in a short time.

In most countries, passive disease surveillance is the main approach to gathering information on disease trends in a population. Health care workers submit reports of suspected cases of communicable diseases to a central database, and regulations requiring notification of these events by health practitioners make the process more reliable than in the past.

In order to be effective, surveillance needs to detect the emergence of new disease-related patterns quickly. This can be difficult, especially if the correct baseline is not established. This is because several confounders influence the accuracy of a signal, such as trends in 911 calls, school and work absenteeism, or sales of certain pharmaceutical drugs. According to Advance On-site Protection Security, notifiable diseases are those that are identified as having a significant impact on public health and for which interventions exist. Surveillance is conducted on these diseases at the national level.


Observation from a distance is a common technique used in surveillance technology, but interception of data is also a major method employed. Examples of this include monitoring live video feeds, which are often used in large commercial areas, access control points at shops, residential buildings, and communities, as well as at many government and private institutions. Usually, on-location human guards monitor the live video surveillance system during active hours, but remote monitoring online is also a common practice offered by security companies. Other methods of surveillance through intercept are tapping telephones, either officially or unofficially, which is common in many countries; speech-to-text software converts audio into machine-readable text and is a popular technology in call analysis programs. Interception of mail through postal services is a declining but still popular form of surveillance. GPS tracking devices and listening bugs (sometimes known as ‘spy cameras’) are increasingly used to track and record activity and can be attached to vehicles and people.

The type of surveillance used varies depending on the investigation being undertaken and can be overt or covert. Overt investigations, such as insurance or spousal investigations, use physical observation and can require stakeouts, disguises, and multiple investigators. Covert investigations, such as espionage, can be carried out using electronic surveillance equipment, including cameras and computer analysis, and can involve covert techniques like bugging or tampering with a device.

Health surveillance aims to detect, evaluate, and respond to disease outbreaks through population-based monitoring. It is based on data that may be collected from various sources, including ambulance runs and chief complaints of 911 calls, hospital admissions, school or work absenteeism, and trends in pharmaceutical and laboratory demand. The effectiveness of health surveillance depends on accurately determining the correct baseline and identifying early signals that might indicate a change in disease-related patterns.

Surveillance can be a powerful tool in the hands of those with the right resources, but it is important to recognize that it can have negative effects on an individual’s privacy and civil liberties. For this reason, it is important to ensure that any type of surveillance is authorized and justified by the authorities that are carrying out the activity.


When you monitor something, you pay close attention. It’s a form of observation that private investigators and security specialists can use to keep track of suspects or even infiltrate organizations without their knowledge. Businesses also commonly use monitoring to prevent crime and protect their assets. It’s a common practice among police forces, too, when they watch a criminal stealing merchandise from a store.

Covert surveillance techniques are a type of monitoring, such as a hidden video camera or audio recording device. These methods help to reduce the risk of discovery by removing the need for humans to monitor situations around the clock. For example, a business with a fully managed CCTV system from a security company will only need to monitor the videos it captures on a regular basis. This means there is less need for people to scout the site for signs of criminal activity, and more time can be spent on other security activities.

Different surveillance technologies will be employed depending on the purpose of the investigation. For example, stationary technical surveillance involves a device that is fixed in an area of interest, such as a car with a concealed recorder and hidden cameras. This is often a cost-effective option because it allows the investigator to focus on one location at a time while providing the flexibility of coming and going from the area as needed.

Physical surveillance, on the other hand, is a highly specialist technique. Private investigators and security specialists will use this to monitor individuals or groups of people, especially if they know that those individuals are likely to move from place to place. This can require stakeouts, disguises, and multiple surveillance officers working together to achieve results.

Event-based public health surveillance is a type of monitoring that looks at reports, stories, and rumors about health events that may pose a risk to the population. This is combined with laboratory, physician, and population surveys to identify and track disease patterns and trends.

While all of these monitoring activities are valuable tools, they can be difficult to evaluate. It’s important to have a clear understanding of the goals of any surveillance strategy before it’s implemented. The information collected should be measurable so that it can be compared against benchmarks. This is particularly important for the evaluation of larger-scale prevention and control measures, such as nationwide disease surveillance.

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