BEST SECURITY DRONES: 5 KEY FEATURES

Security Drones are being used in a wide variety of security applications, from patrolling borders and conducting 24/7 surveillance of huge sectors to responding to early warning triggers and conducting initial assessments. But there are a few things prospective enterprise drone customers need to know.

The introduction of low altitude sUAS (small Unmanned Arial Systems) as Security Drones in the overall remote sensing environment has brought significant advantages on previous methods for ISR (Intelligence, Surveillance, Reconnaissance) operations. This article describes what to look for to select the best security drones.

Firstly let’s have a look at the overall landscape for UAS and where low altitude Security Drones would fit in with this graphic by the US Department of Homeland Security.

Categories of UAVs and where security drones fit in
Categories of UAVs

Low altitude sUAS fills a particular gap in UAV airspace by bringing the power of previously space-borne, HALE or MALE-borne, or terrestrial remote sensing technologies airborne to within less than a few hundred meters of identified targets.

With these security drones early warning and real-time Situational Awareness (SA) is delivered at a fraction of the cost of HALE (High Altitude Long Endurance), MALE (Medium Altitude Long Endurance) or Satellite alternatives which tend to provide delayed, ‘after the fact’, information.

Covid-19 and other changes to the geopolitical landscape means more unrest and challenges to security. Security challenges means more Border Management to deal with trafficking, smuggling, etc. Other than Border surveillance, Surveillance of illegal activities, terror operations, piracy operations, maritime traffic surveillance, anti-human trafficking operations, anti-poaching operations and surveillance of hostile situations are ideal applications for Security Drones. See the Surveillance and Security applications.

Example: Some of the advantages of low altitude Security Drones for Border Control:

  • UAVs provide a rapid response and fast “eyes on” to the target area with live updates to control stations on land AND water
  • The speed, size, manoeuvrability and additional technologies make UAVs the ideally suited for ISR or rapid SA for BOTH ground- or water-borne units to detect and monitor potential threats from a safe distance.
  • Stationary cameras  – have blind spots
  • A physical wall (or infrastructure) – once built, cannot be redeployed, or adjusted.
  • Border patrol agents would take an hour, on land or water, to reach a trigger event 10kms away, – a drone can be there, AND overhead, within minutes.

THE 3 MAIN AREAS THAT SECURITY DRONES IMPROVE SURVEILLANCE AND SECURITY

The well-known Endsley model below describes the ISR process which is often also represented by the OODA model (OBSERVE, ORIENT, DECIDE, ACT). Low altitude drones are better able to provide improved capability across the full ISR methodology from DRI, SA to OODA.

  1. Being able to bring more powerful sensors closer to the target/s than before enables higher levels of DRI (Detect, Recognise, Identify) during the OBSERVE phase.
  2. This in turn leads to higher levels of SA (Situational Awareness) insight during the ORIENT phase.
  3. This in turn leads to much faster and more effective responses during the DECIDE and ACT phases.
a model to describe the impact drones have on an ISR model
ISR Model with DRI and OODA

Security Drones are deployed in different ways for security and surveillance purposes:

Fixed-wing drones are capable of covering vast distances and typically have significantly longer flying times per charge than multi-rotor vertical takeoff and landing (VTOL) drones, but sacrifice the agility necessary for many inspections and close-quarters applications. Fixed-wing VTOLS add VTOL capabilities to a fixed-wing drone offering the best of both worlds.

Different models of deployment

– Regular patrols for early detection, like the Predator drones on the USA/Mexico border

– Ad hoc incident response to initial detection for “eyes on” closer scrutiny

– Persistent surveillance of hotspots 

– Ad hoc incident respond with remote robotics intervention

– Level of automation (‘Drone in a Box’) applications

Depending on the deployment requirement different UAV models may be selected to meet specific mission requirements.

THE 4 MOST IMPORTANT FEATURES OF SECURITY DRONES

1. NOISE FOOTPRINT

Most surveillance missions are their by their nature discreet and it is important to understand the noise footprints of various drones and what your requirements are in terms of location and level of detail to be captured.

Noise from a drone is only relevant to the extent that it does not exceed ambient (background) noise levels in order to avoid detection by the objects (human/animals) of interest.

Ambient noise obviously differs from CBD to SUBURBAN to RURAL (Wilderness) conditions, as well as from day to night time. The ability to be undetectable in the Rural setting being the highest level of stealthiness.

Ambient Noise Ranges: When is a drone quiet enough?

Contrary to widespread expectations, ambient noise levels in a Rural setting seldom drop below 35dBA (night-time) and 45dBA (daytime).

For both security and wildlife monitoring operations in the Rural setting, the ideal drone noise range would be 35 – 45dBA.

QUIET DRONE DESIGN Given the importance of stealthiness in surveillance applications, some commercial drone manufacturers specialize in silent drone design by using specific motors, propeller and aircraft body designs to gain significant reduction in noise levels of up to 10dBA. The following list compares the design objectives of certain classes of drones: 
Consumer drones   (Typically designed to meet certain price points)
Quiet Commercial drones (Designed for noise reduction as well as endurance, efficiency and flexibility)
Fixed Wing UAV – Electrical  (Designed for energy efficiency)
Fixed Wing UAV – Petrol (Designed for endurance)Obviously not all drones are designed with a limited acoustic signature in mind. 
Different drone design objectives

The following graph depicts the noise fall-off rates over distance for a selection of UAV configurations and compares them to certain levels of ambient (background) noise:

Noise fade-off rates for various drones

read more about drone noise levels..

2. ENDURANCE

For Security Drones endurance (Flight-time) is important not only because of the extra reach that it enables but also for persistent surveillance improved responsiveness. Longer flight-times reduces the time wasted with landing and relaunching as well as exponentially increasing the potent strike range for every extra minute in the sky.

Flight limitatiomFlight timeFlight distance (60km/h)Potential area of coverage (strike range)
VLOS30 seconds500m0.79km2
EVLOS1.5 minutes1.5km7.07km2
BVLOS30 minutes30km2,827.43km2
Potential Area of coverage for different security drone flight ranges

*Extended/Beyond VLOS (Visual Line of Sight)

Security Drones with VLOS, EVLOS and BVLOS ranges
Potential Area in any direction that can be covered depending on radius (range)

3. RANGE

When security drones endurance (Flight-time) translate into flight distance or area covered long Range for Telemetry and Video Feedback to Command and Control stations is essential.

4. PAYLOAD

The most important consideration for prospective enterprise drone customers is sensor package. Will the UAV operate during daylight hours and cover relatively open terrain? Specialized use cases required more sophisticated equipment. 

Thermal sensing helps identify body heat from humans and animals even when there’s dense ground cover or vegetation, making it essential in wilderness applications or if drones fly after dark. Radar, with its high-fidelity point clouds, are great for monitoring hidden targets irrespective of weather conditions. 

Endurance and Range are of limited value if these do not result in the right capabilities are brought to identified target areas. The best security drones benefit from being able to integrate a variety of previously space- or terrestrial-borne, remote sensing technologiesinto SWAP (small size, weight, and power consuming) designs for low altitude sUAV platforms. 

The lowest undetectable altitude impacts achievable GSD and thus the details that can be detected from the sensor bearing in mind that when conditions are poor up to 180 pixels/ft may be required to identify a human.

A comparison of the generic classes of sensors follow:
Generic SensorsApplications 
RGB camerasVisual analysis, mapping, land cover/land use, classification, pedestrians and vehicles detection and tracking, etc.Advantages: (1) high availability in products ranging across different levels of cost, resolution, and weight; (2) easy to be integrated in different platforms (3) well-modeled camera geometry with a large number of software solutions; and (4) videos.Disadvantages: (1) Often come without radiometric/geometric calibration; and (2) lack of spectral information for many tasks.
 Light-weight multispectral camerasVisual analysis, vegetation detection and analysis, crop monitoring, mining,soil moisture estimation, fires detection, water level measurement, land cover/land use mapping, etcAdvantages:(1) wider spectrum range and narrower bandwidth; (2) often come with means of radiometric calibration; (3) most of the sensors still follow a perspective model that can be well-processed for geometric reconstruction; and (4) allow for sub-decimeter multispectral mapping. Disadvantages:(1) data format compatibility (sometimes 12 or 16-bit) for software packages; (2) as a component of a UAV system, its cost remains to be relatively high; (3) sensor compatibility to drones may be limited; and (4) videos may not be available.
Hyperspectral sensorsLand cover/land use mapping, vegetation indices estimation, biophysical, physiological, or biochemical parameters estimation, agriculture and vegetation disease detection, disaster damage assessment, etc.Advantages:abundant spectral information, 10 nm-level bandwidth for more advanced applications in material identification and so on. Disadvantages:(1) high cost; (2) most of them are linear-array and require specialized software, and the users may take care of the data format and geometric corrections; (3) dimension reduction is needed for typical classification tasks; (4) sensor compatibility to drones may be limited; and (5) videos may not be available.
 Light-weight thermal infrared sensorsTracking creatures, volcanos detection, forest fire detection, hydrothermal studies, urban heat island measurement, etc.Advantages: (1) well-targeted sensor for surface temperature measurement that drives a lot of new applications; (2) the camera model is normally perspective, and relatively easy to be processed than linear-array cameras.Disadvantages: (1) lack of texture information of its imageries brings difficulties in 3D reconstruction tasks; (2) for direct temperature measurement, it needs careful calibration; (3) cost is relatively high comparing to that of RGB cameras; (4) comparatively lower resolution than that of RGB cameras due to sensor design; (5) sensor compatibility to drones may be limited.
UAV LiDAR & SARVegetation canopy analysis, estimation of forest carbon absorption, mapping cultural heritage, building information modeling, etc.Advantages:(1) direct geometric measurement; (2) multiple returns of the signals are useful for terrain modeling under thin canopies. Disadvantages:(1) high equipment cost; (2) highly dependent on expensive onboard GPS/IMU measurement (potentially with external reference stations); (3) increased payload for surveying quality LiDAR; (4) may not work in GPS-denied regions.
overview of generic classes of sensors
For Security Drones specifically the following sensors are most effective:
  1. ELECTRO-OPTICAL SENSORS like infrared sensors, visible-light cameras, multispectral, and hyperspectral sensors
  2. small power-efficient RADAR SYSTEMS suitable for unmanned vehicles, 

Further functionality to enhance the effectiveness of Security Drones include digital signal processing to make sense of sensor information and pull out relevant information, as well as sophisticated networking to blend information from many different unmanned sensor payloads to provide a rich information picture for command and control.

ELECTRO-OPTICAL SENSORS

These sensor payloads are used in various surveillance and reconnaissance applications from counter-drug operations, homeland security, search and rescue border control, military, and a variety of civil applications. They comprise compact multi-sensor gyro-stabilized surveillance system for SWaP platforms with electro-optical four-sensor payloads using four-axis stabilization with digital inertial measurement unit with Global Positioning System receiver for geo-pointing and target geo-location capability and options for laser range finders.

RADAR FOR sUAVs (LIDAR & SAR)

Most importantly about these systems operates day or night, in rain, snow, fog, dust, or smoke to enable detection, location, and classification of targets.

Radar (LIDAR & SAR) systems are now becoming available sUAVs for surveillance, as well as for sense-and-avoid operations. Using artificial intelligence (AI) algorithms to provide situational awareness for safe unmanned aircraft operations radar provides detailed real-time aerial radar images, while delivering precision air-to-surface targeting accuracy and superb wide-area search capabilities.

Operating Modes for SAR

  • Using ground/dismount moving target indicator (GMTI/DMTI), and maritime wide area search (MWAS) search modes to provide the wide-area coverage and allow for cross-cue to a narrow field-of-view (FOV) electro-optical/infrared (EO/IR) sensor.
    • The GMTI mode helps locate moving vehicles, while DMTI enables operators to detect very slow-moving vehicles and people on foot.
    • MWAS mode detects ship and boat traffic in various sea states; it also integrates automated identification system (AIS) information for target correlation and identification and is suitable for coastal surveillance, drug interdiction, long-range surveillance, small target detection, and search and rescue operations.
    • UAV based SAR can detect resolutions as low as 0.3 meters and wit a detectable range of up to 10 kms.
  • SAR imagery can also help detect subtle changes in a scene by overlaying two images taken at different times. Coherent change detection (CCD), amplitude change detection (ACD), and automated man-made object detection (AMMOD) algorithms are able to rapidly highlight the differences between the first and second SAR image for analysis.

read more about SAR applications…

5. SPEED

Speed is often overlooked in the assessment of drone performance where the focus tends to be on flight time (endurance). The real efficacy of a Security Drone is bringing the right capability to the right area at the right time. This means delivering timeous feedback, even during a long range mission.  

At 60km/h, conventional UAVs cannot achieve much efficiency if they reach long range targets belatedly.  At 200km/h high-speed low-altitude drones would reach a target 60km away in 15minutes, a conventional UAV would still be 45km away.

A high speed security drone can achieve 3 to 4 times more in a a straight line and 10 to 18 times more over a strike area
The difference speed can make in one hour

read more about high speed drones

CONCLUSION

Security and surveillance are one of the biggest growth areas in the fast growing UAV sector. 

Smaller and cheaper SUAS security drones and therefor able to cover much more terrain than ground-based surveillance systems and more efficiently than manned-aircraft like helicopters.

But being able to cover large areas with Security Drones is useful – as long as this is being done effectively, rather than just efficiently. Servicing the full ISR process can require the deployment of a variety of different Security Drones whether it is stealthiness, responsiveness, range, or level of response.