By AeroDefense on September 20, 2022

Drone Detection Technology for Correctional Facilities

Before evaluating or purchasing drone detection technology, it’s important to define needs. Different facilities face different risks, and a single facility’s risk can change with as little as an inmate population change.

Drone detection sensor type and configuration depends in large part on the risk assessment for each facility but let’s face it, budget is always a challenge.

For example, super-max facilities housing the most violent offenders present a different, much higher risk profile related to drone-borne contraband deliveries than low, medium or juvenile facilities.

Because of the super-max facility’s heightened security concerns, they may determine they need a permanently installed full coverage, radio frequency, radar with integrated pan-tilt-zoom camera multi-layer deployment that extends pretty far beyond the prison grounds.

Lower level facilities may only need airspace awareness and a proximity alert that a drone has crossed the boundary into the facility.

The drone contraband risk profile for a low or medium housing facility can vary by the inmate population itself which can change quickly when a high-level gang member transfers into a facility. A low-medium facility’s need may switch from simple airspace awareness when a drone crosses the facility boundary to the need to detect and locate multiple drones and pilots.

Drone Detection Sensor Types 

The Federal Aviation Administration (FAA) divides the four (4) drone detection sensor types into two (2) categories: Primary and Secondary.

According to the FAA, “Primary detection sources are those sensors that have a greater level of system autonomy, providing alerts to be generated upon a detection, prompting further investigation by the detection system operator.”

In other words, primary sensors are able to detect drones with high enough accuracy and low enough false alarm rates to operate as standalone solutions. That is, they do not require data from other sensor types in order to validate their detections.

Primary Sensors

      • Radar
      • Radio Frequency (RF)

Secondary sensors need additional data from other sensor types in order to accurately detect drone threats. These additional sensor types can be used to enhance the accuracy of – or provide more detail about – drone threats, but they should not be used as a standalone system.

Secondary Sensors

      • Acoustic
      • Camera/infrared
Sensor Type Pros Cons
Camera/IR (Secondary)
  • Easily acquire visual evidence
  • Must be combined with another detection method to guide camera angle
  • Requires line of sight
Acoustic (Secondary)
  • Does not require line of sight
  • Must be combined with another detection method
  • High false positive rate in noisy urban environments
  • Very short range due to ambient noise
Radar (Primary)
  • Detects radio-silent drones
  • Detects anything that moves, therefore a high false positive rate in a busy environment
  • Requires line of sight
RF (Primary)
  • Only solution that can reliably detect both controller and drone
  • Does not require line of sight
  • Systems must be configured to filter out ambient RF signals
  • Can have high false alarm rate in busy environments 

Camera/IR (Secondary)

Because drones are so difficult to see, most cameras have a fairly short range of under 300 meters and require some primary alert system to notify the operator of drone presence.

Cameras coupled with Artificial Intelligence to detect drones work well on a blue-sky clear background. Once the drone moves to a cluttered background such as trees or buildings, the systems struggle substantially.

Weather and lighting conditions can adversely affect camera operations. Once the sun goes down, infrared camera capability would be required to see anything typically outside a prison boundary. Inside, of course, it’s still bright enough to see day or night.

Since most existing camera networks are pointed to the ground, they will not be very helpful to see drones in the air and should not be used as a standalone drone detection system.

One way to leverage existing camera networks to get eyes on the pilot is for an RF or radar drone detection sensor to automatically tell a Pan, Tilt, and Zoom (PTZ) camera where to point to see both the drone and the pilot either in real-time or video review.

Acoustic (Secondary)

Trains, buses, jack-hammers and everything in between generate noise that hides drone sounds. Even in quiet areas the acoustic detection range is very short, so the technology does not seem feasible for drone detection at a corrections facility.

Radar (Primary)

Radar detects non-RF drones. While the vast majority of drones on the market use RF, some drones can operate without RF communication, and well-informed contraband delivery operators may use shields to attempt to mask the RF signals.

Radar detection is a transmitting technology so facilities must ensure the radars will not interfere with any other equipment. The facility must apply for the proper authorizations to deploy transmitting radar technology.

Radar requires line of sight which can make sensor placement at a corrections facility a challenge.

Birds, plastic bags and even wind that makes tree branches move and flags fly briskly can be a source for radar false alarms.

When radar and RF are combined, they can complement each other. Radar can detect non-RF drones and the RF system can detect and locate the pilot and drones potentially before take-off. Each system can validate the other’s detections to reduce false positives.

RF (Primary)

RF sensors emerged as the leading drone detection technology because they are the only type that reliably detects both the controller and drone, require little maintenance and operate in all weather conditions.

Since RF-based systems operate in different ways, there are several important considerations to determine which system will be the best fit for your facility. Here are a few key questions to help you evaluate:

Drone and Controller Detection Information

      • Can the system detect and locate multiple drones and pilots simultaneously?
        • Sophisticated contraband delivery operations use lookout and decoy drones while the delivery is underway.
      • What kinds of drone manufacturers does the system detect?
        • Facilities can no longer assume all drone pilots fly DJI drones. According to a recent report, DJI continues to lose market share and now only claims 54%, 15 points less than the previous year.
      • Does the system rely on a product library?
        • If a system relies on a product library, it must be manually updated when new drones hit the market and will not detect kit, custom drones used by nefarious actors.


      • How quickly will the system alert me to drone activity?
        • Some RF-based drone detection systems can alert as soon as the drone is turned on and establishes a connection with the controller to provide security teams maximum response time. If a response team acts quickly enough, they may be able to stop the operation before it even happens. Some contraband pilots will test security responses ahead of time which presents an opportunity to deter them away from a facility.
      • Can I change my alert zone to only alert my facility when drones/controllers are within a certain distance?
        • Some facilities may not want to know when the farmer nearby is flying their drone. A system configurable alert zone offers flexibility.
      • How many false alarms can I expect?
        • Some RF-based systems have high false alarm rates that can lead to staff desensitization. For an RF-based system to be effective it must filter out ambient RF signals. Vendors should work closely with a facility before, during, and after the system is deployed to help properly calibrate the system.


      • Are the sensor electronics and antenna separated?
        • If the sensor and antenna are not separated, deployment options are limited and could be more costly. Heavy equipment mounted at the top of poles causes wind load concerns.
      • Does the system use one sensor type to detect and locate or one sensor that detects and another that locates?
        • Systems that use disparate sensor types suffer from a single point of failure if the single detector sensor type is disabled or goes offline.


      • Will the system give me the drone’s serial number?
        • While this is not the only question regarding system legality, it is the easiest way to determine if a drone detection system violates federal surveillance laws today. Currently, no drone detection system can legally extract this information from the drone signal. When the FAA’s Remote ID rule compliance date arrives, a unique identifier for the drone, among other device information, will be publicly broadcast. But it is unlikely contraband pilots will use drones that comply. 
Published by AeroDefense September 20, 2022