Spotting a drone at night can be relatively difficult due to the fast-moving nature of drones and the fact that most trends allow you to turn off the lights during use. There are many reasons why someone may want to fly a drone night: it may be the police looking for a suspect, it may be scientists monitoring wildlife, or it could just be someone who wants to infringe on your privacy. In this article we’re going to go through how to spot a drone at night and the advanced technologies that exist for doing so.
You can spot a drone at night by using the sound of the drone to locate its position in the sky, you can spot it optically by using the lights that are on the drone and you can also use a drone detection app to find out how many drones are in your immediate vicinity.
Before we get into exactly how you spot a drone at night we need to understand that not everyone is trying to spy on you or your property. There are a few legitimate reasons for using a drone at night by the police, sciences, security, and other government agencies.
Who is flying a drone at night?
Depending on where you are flying a drone there are a number of rules and regulations which can stop you flying at night. If you are only a hobby drone flyer the general rule is that you need to land your drone at sunset. However, with extra training and certification you can fly your drone night to capture stunning aerial footage of night time cityscapes or other well illuminated areas.
In my experience, it is unlikely that it is a person with extra certification.
Quite simply, flying a drone at night is a fair bit more dangerous than flying during daytime and there is not as much to see.
When you are flying a drone during the daytime you can see all the way to the horizon which makes for an awe-inspiring shot. However, at night time your range is extremely limited unless you are lighting the scene artificially.
Here could be flying a drone at night if you suspect that there is a drone fly above you or your property.
Police
The police use drones for surveilling and locating criminal activity. The police drones tend to be of the larger consumer and enterprise model drones which means that they are much easier to spot and hear.
The reason they are much heavier drones is that they tend to be carrying heavier camera equipment and also extra functionalities such as lidar and thermal imaging capabilities. This requires a much more powerful drone with more propellers – up to 6 – for stability and lift power.
If you suspect that the police are performing operations in your area you can often get information about the training or incident on social media and the local police communication channels.
Security
Security operations should only really happen over private property. If you live close to a private plot of land you may see drones flying over the area. They are typically monitoring for people that shouldn’t be on the property and also monitoring asset locations to make sure that nothing has been stolen or moved.
Quite often these are mid-range to large drones as the drone will also be carrying a thermal imaging camera.
Scientists
Scientists use drones equipped with thermal cameras for estimating wildlife populations. If you live near a wooded area or an area high in wildlife activity you may find that scientists fly at night to count the thermal signatures from nocturnal animals.
There are a range of different studies which drones are used to count and monitor wildlife but the data collection. Should only last a few weeks at the most.
Perverts?
If we hear a drone flying in the local area are first instinct is to think about how it is impacting us and our privacy. From experience, it is very hard to identify individuals from any significant distance using a drone unless you have a drone with a high capacity zoom.
If you suspect that you are being targeted by a drone pilot and it is infringing on your privacy you should report that to local law enforcement officers as soon as possible.
My first inclination is to assume that they are not in the area flying at night to find out what I am doing but it is one of the other types of uses that we talked about, above.
Here are all of the ways that you can identify a drone at night – even if you can’t see it.
Noise
The noise that a drone makes is very distinctive. Depending on the type of drone that is being flown anywhere from a swarm of bees all the way down to a low pulsating frequency.
Once the drone passage is about 60 m it is typically much harder to hear. However, night because it is so quiet you can typically hear a drone when it is flying much higher. This means that the drone can sound closer than it really is at night time.
Pitch of the sound
The pitch of the sound of each drone varies wildly depending on type of drone that is being flown. Here is a link to a wide range of different drones as well as a few noise comparison videos.
| Drone noise comparison | Link |
|---|---|
| Mavic pro versus phantom 4 pro | YouTube |
| DJI inspire one | YouTube |
| Phantom 4 | YouTube |
| Mavic mini versus Mavic air | YouTube |
| DJI spark, Mavic air, Mavic pro, Mavic pro platinum, Phantom 4 pro | YouTube |
My DJI Mavic air sounds much higher pitched than a number of different drones on the market. It very much sounds like a swarm of bees – which is probably why it has been attacked by bees so often –To find out more about why drones attack these check out my other article – click here.
Other, larger drones, make a very different sound. Here are the three reasons why drones make so much noise while they are hovering and flying:
- Propeller rotation frequency – if the propellers whip through the air quickly we get a higher frequency generated. There is not much you can do about the drone requiring a high rotational frequency. That is what keeps it in the air. However, you can choose a drone that is larger and has a slower rotational frequency to avoid the high-pitched “swarm of bees” sound.
- Propeller blades passing over arms – one of the main reasons drones make a high sound is that the propeller blades have to pass over the arms which hold them out beyond the body of the drone. As the propeller blades pass over the arms it temporarily creates a high pressure system over the arm and stops producing pressure under the aircraft. This creates a pressure wave and a sound which is a fairly low frequency.
- The size of the drone – the weight of the drone will dictate how fast the propellers have to spend to generate the don’t thrust that is required for it to hover. If you are buying a heavy drone the propellers will spin faster and will be much louder. Think of a helicopter as being the ultimate loud heavy drone for comparison.
- The length, pitch and depth of the propellers – larger propellers this place more air while they spin that means they produce more thrust and require less of a rotational frequency to keep the drone in the air. The sound is also changed by the angle, or pitch, of the propeller as the pitch determines how much disturbance it causes in the air.
Sound changing location
Another very important identification tool for how to spot a drone at night is now fast the noise use through the sky. We are very familiar with how quickly a helicopter moves through the sky and its volume combined with its high altitude travel means that the sound doesn’t move location very fast. I.e., the noise stays around for a while.point
Drones, the other hand, change location very very quickly and their relatively low altitude means that the sound is very different depending on if they are travelling away from you, toward you, or anything in between.
You can make a drone significantly quieter by using different propellers.
Making a drone quieter
There are plenty of aftermarket low noise propellers. If you go to any retailer (such as Amazon) and type in low noise propellers and your model of drone you will find a range of low noise, quick release upgrade propellers for your model. They tend to work in a couple of ways
- they reduce revolutions per minute
- stealth propellers have a very smooth surface.
Typical outcomes of using stealth propellers are a reduction in noise by about 3.5 dB, by reducing the revolutions per minute by about 20%. An added side-effect of super-efficient and smooth blades are that you are likely to get a longer flight time with up to 14% more hovering time.
Although sound is one of the most iconic ways of detecting drones at night you can also use their LED lights for determining if there is a drone above you.
Lights
Drones have a right of LED lights with forwards, backwards, and other directions during flight.
For example, my DJI Mavic air has two forward facing multiple colour LED lights that can change from green, yellow, and red. The colour of the LED relates to the functions that it is performing at the time. For example, the lights turned green if it is recording. It also has a light on the back which can also be green, yellow, or red.
Depending on the type of drone that you expect may be flying around you that colours may differ.
What color lights do drones have at night?
There is no set colour of lights that drones may have at night. For example, if it is a police drone it may have red and blue lights, and if it is a hobby drone it may also have a combination of LED colours.
Types of light on a drone
If the person is following all of the rules the pilot should have attached lights which means that they are able to detect the orientation of the drone at all times.
This means that you would need at least three lights on your drone to know both its location and orientation. A white light on top, a red navigation light on the left, and a green navigation light on the right – this is similar to what aircraft uses while flying at night too.
You can read more about the FAA’s rules here – click here.
By using these lights the pilot would be able to tell which way the drone is pointing and travelling. For example, if you can see a red navigation light on the right, and a green one on the left the drone is travelling towards you.
Not only must a drone pilot attach lights if they are flying at night, but they may also choose to attach spot lights to the arms of the drone during flight. You can add a lighting kit from a company such as LumeCube.
Use a drone detector app
There are a number of apps which you can use but one of the most popular is called drone watcher.
Is there an app to Detect drones?
The drone watcher app turns your android device into a detector of drones and is able to alert you and track their path. The app detects most commercially available consumer and prosumer drones and records the data including the drone type and ID which can be used to document evidence to be used by local law enforcement.
Will a drone show up on radar?
Whether or not a drone shows up on radar will depend on the type and size of drone that is flying. Typically, raiders are used to detect large objects in the sky and it can be difficult for them to detect small drones.
It really depends on what is called the radar cross section of the drone. Essentially the larger the cross-sectional area the more likely it is to be picked up by radar technology.
There is a fair amount of interest in detecting drones for security and military operations. And the science is slowly building up ways to detect drones using different types of radar technology. For example, a publication from 2020 shows that you can use a special to the radar that uses a millimetre wave detection system to estimate the 3D position of the target drone stop the method was validated and it was shown to be effective in the field against two drones of different sizes that were purchased commercially and available to the general public.
Furthermore, a publication from 2018 showed that there are a range of different options such as ambient radio frequency signals, radar, acoustic sensors, computer vision techniques, and more for the detection of drones.
This is a rapidly developing area of science and we are learning more and more about how to detect drones easily and simply using radar, and other common technologies.
Thermal detection
As drones are flying through the air they build up their amount of heat. This is because there is a rapid exchange of energy from the battery to the motors. This quick exchange of energy quickly heat up the circuit boards in the drone which means that they are susceptible to being detected by thermal cameras.
Especially in the darkness of night.
Radio-frequency detection
Drones can be detected by monitoring the radio frequencies that they use to communicate between the remote controller and the drone itself.
As you are flying a drone there is a continuous two-way data transmission between a drone and the pilot on the ground. The data is sent in various frequency bands which means that there is a lot of opportunity to detect the drone. One of the benefits is that there is no need for signal sending and it can be detected passively.
Drone Micro-Doppler
You can also detect a drone by monitoring the air currents that they produce. A micro-Doppler is able to detect the small air currents that are produced by the propeller. A study published in 2018 showed that you are able to use micro-Doppler measurements for detection and classification of small drones.
Micro-Doppler are Doppler shifts generated by the movement of the internal parts of the target drone. This particular movement is able to be used to distinguish drones from birds by extracting the unique radio identifier.
The scientists conclude that micro-Doppler radar has the potential for reliable small drone target detection and is also a promising candidate for being able to classify the type of drone as well.
Summary
In this article, we’ve gone through all of the ways that you can spot a drone night. You can use the drones noise, sound, thermal properties, and radio-frequency emissions to detect the drone if it is flying above you or your house.
Ultimately, if you suspect that someone is flying illegally above you or your property or you are worried about your security and privacy you should speak to your local law as possible.
