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SPI offer specialist technical surveillance services tailored to individual requirements.

What is Technical Surveillance?

Technical surveillance is a form, or forms of surveillance where a data capturing device is required to assist an investigator in completing his or her investigation. Such devices come in various forms and are selected to maximise collection of relevant data. In other words, choosing the right tools for the right job. Technical surveillance devices are usually deployed discreetly and out of view to the naked eye to ensure they function without interference from third parties or the data subject.

GPS Vehicle Trackers

GPS vehicle tracking services

GPS vehicle trackers are used to monitor a vehicles movements and locate its whereabouts. GPS vehicle Trackers are a highly effective piece of technical surveillance equipment as they can save a surveillance operation (which the client has likely paid a lot of money for) from coming to an abrupt end. Sentry Investigations Ltd use GPS vehicle trackers as an aid to surveillance in order to prevent losses of contact with the vehicles we are physically following. Loss of contact during surveillance is a very real possibility, but with the use of GPS vehicle trackers, this possibility is extinguished.  We follow guidance and best practice procedures for the use of GPS vehicle trackers as documented by the Association of British Investigators. This is to ensure our operations are conducted legally and ethically whilst adhering to UK privacy laws. To find out more about GPS vehicle trackers, please visit our GPS Vehicle Trackers page. 

Aerial Drone Surveillance 

Drones have come a very long way in recent years and they are proving to be an invaluable tool for many private investigators that specialise in covert surveillance operations. Aerial surveillance drones are excellent for reconnaissance, observations and security measures, and they provide us with crystal clear imagery from very long ranges. We often find drones make light work on tasks where surveillance operators struggle to observe hard to reach properties with extensive grounds or in rural areas. Modern drones are fast becoming a camera of choice for private investigators as they are quick to deploy, they are small in size, they are quiet but most of all, they provide us with vast amounts of intelligence that we would not normally be able to achieve. 

There are of course limitations and laws to be considered with the use of drones, especially when it comes to surveillance and private investigations. As per our regular surveillance operations, we take privacy and data protections laws very seriously. These laws can easily be broken with a drone thats fitted with a 4K camera, which is why we regularly familiarise ourselves with laws and local bylaws to ensure our aerial drone activities are conducted with a professional and legally sound approach.

drone surveillance private investigation services

SPI Professional Associations

ABI Logo

Association of British Investigators

armed forces covenant

Armed Forces Covenant Bronze Awarded

institute of professional investigators

Institute of Professional Investigators

UK PIN logo

UK Private Investigators Network

Static/Hidden Cameras

Static cameras are an excellent form of technical surveillance equipment. Technology has come a long way over the past few years and it has enabled us to deploy these covert cameras for weeks, if not months on end without the requirement of an external power source due to its internal battery capacity. They can discreetly lay dormant over long periods of time and then record in high definition as soon as it detects any movement. Much like the security door bells we are seeing more of, only these cameras do not require a Wifi signal. They actually run off a 4G network allowing us to be notified on our phones which we can view as a live stream anywhere in the world. Recently, we have been deploying static cameras more and more often. They are a cost effective way for certain clients to receive the information they are seeking as they can replace the need for more expensive manned surveillance operations.

hidden covert camera deployment services

Static camera deployments can be utilised for a whole host of legitimate reasons, but they are a perfect solution for catching cheating partners bringing home 'other partners'. They can even tell you when the 'other partner' leaves the home. A surveillance operative could be compromised gathering this sort of information, whereas it is highly unlikely one of these discreet cameras will be found.

Listening Devices
listening device deployment private investigation services

Listening devices are a tool used to gather evidence of conversations. They are typically small in size and can come with various functions such as 'standalone' where the device has an internal memory and does not emit any signal. The devices are more difficult to locate during a TSCM bug sweep, but not impossible. Other devices do emit a signal where operatives can dial into the device and listen to the conversations as they are happening. They often do not use much power when in operation so they can remain dormant for very long periods of time. 

As with all technical surveillance devices, listening devices must only be utilised in certain circumstances where there is a legal basis and not to invade in peoples personal privacy. 

Within the corporate sector, listening devices can and are used to evidence suspected industrial espionage. This method of evidence gathering would be deemed proportionate to the situation and can protect a company from going under. Private sector circumstances may include infidelity within a relationship providing permission from the home or property owner is given to the investigator to deploy such a device. In any case, a client should always seek professional advice prior to the use of this and any technical surveillance service to avoid any serious legal repercussions.

Standards of Our Technical Surveillance Services


Our private investigator technical surveillance services are delivered with integrity and professionalism on all accounts


Our private investigations are conducted with robust ethical standards and accountability at all levels


The technical surveillance services we provide are in compliance with UK privacy and data protection laws


A quality service at a cost effective price is what we deliver with both our private investigations and corporate investigations

Find Out More

If you wish to find out more about GPS vehicle trackers, unmanned cameras or any other technical surveillance solution we offer, get in touch with SPI today. We offer a free no obligation consultation for the use of our services, and we give guidance on how best to proceed with your investigation. 

Call us on 01217691626 or 07730695853

Email us at

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