Obstacle avoidance is a handy feature on drones but it’s important to understand the limitations and different types of object avoidance. In this article I’ll go through the best drones with obstacle avoidance, the different types of obstacle avoidance and how it works.
If your buying your first drone you may also be interested in checking out my recommend drone for beginners from $50 to $500 because quality drones with obstacle avoidance tend to cost upwards of $1000.
What is Obstacle Avoidance on a Drone?
Obstacle avoidance uses sensors to detect objects in the flight path of the drone and automatically pilot the drone around the object or hover in place if a safe route can’t be detected.
Limitations of Drone Obstacle Avoidance
While obstacle avoidance is a handy feature to have, it’s important to understand what it can and can’t do.
Drone obstacle avoidance technology is improving but it won’t detect fine objects like power lines or thin tree branches well.
Obstacle avoidance can also be too restrictive if your flying in confined spaces. It needs at least a few meters for the drone to fly through a confined space, obstacle avoidance in a tight area will just result in the drone hovering and not following your commands.
Why isn’t obstacle avoidance working on my drone?
Most drone manufacturers have obstacle avoidance active by default but there are a few reasons that it might be deactivated or not working.
Obstacle avoidance doesn’t work in all flight modes. For example, in the DJI Mini 3 Pro, obstacle avoidance is disabled in sport mode and some intelligent flight modes such as Point of Interest and Parallel.
The sensors used for obstacle avoidance don’t work properly when flying over the following surfaces:
- Single color surfaces (ie the surface is all pure black with no texture, pattern or color change)
- Highly reflective or transparent surfaces
- Water
- Moving surfaces
- Frequent lighting changes or very dark/ bright surfaces
- Small or fine obstacles like tree branches
How to trouble shoot when obstacle avoidance is not working properly:
- Clean the sensors
- Review the distance to obstacles and the flight trajectory (the object may have been out of range for the sensors)
- Check the lighting is adequate (<100 lux is too low light)
- Look for sources of interference (ultrasonic devices with a frequency of 40kHz) or test the drone in an open area with less sources of interference with a single object to avoid.
How does obstacle avoidance on a drone work?
There are many types of obstacle avoidance sensors used in drones and most will use more than one type.
Most measure the time it takes light particles or a burst of sound to hit an object then return to the sensor. These returning photons or sound waves form images when processed by the software then the drone automatically steers away from the object.
- Infrared (IR) Sensor: These sensors detect changes in light waves in the infrared wavelength (heat radiation). They are often used as motion detectors to turn on lights or start security cameras as this heat radiation is effected by humans. Infrared sensors are generally low cost as they can be mass produced. These are a form of sensor used in thermal drone cameras.
- Stereo and Monocular Vision: Stereo vision in drone obstacle avoidance works like our eyes. Light is received by two sensors in different locations and forms an image. Monocular vision uses a single sensor rather than two.
- Ultrasonic Sensors : This type of sensor uses sound waves to detect objects, a ping of sound is emitted outside of our range of hearing. The speed of sound is known so the software measures how long the sound takes to return to the drone, if there is a very quick returning sound wave the drone realizes that an object is close by and changes course.
There are many other types of sensors such as time of flight and LiDAR (light detection and ranging). All of these work in a similar way, measuring and monitoring light and sound…. But this is over and above what you need to know as a beginner!
Types of Obstacle Avoidance on Drones
Obstacle avoidance on drones is categorized by the amount of coverage it provides. This depends on the number and position of the sensors:
- Single Direction: This term is rarely used in reference to drone obstacle avoidance because it’s associated with a sensor on the bottom of the drone that positions the drone at a set height above the ground. These are more commonly referred to as downward sensing systems. E.g. DJI Avatar
- Bi-Directional Obstacle Avoidance: Bi directional obstacle avoidance senses objects in two directions (forward and underneath the drone). This requires at least two sensors. The forward sensing system is often two sensors with an overlapping range. E.g. DJI Inspire 2
- Tri-Directional Obstacle Avoidance: Tri-directional obstacle avoidance senses objects in-front, behind and below the drone. This type of obstacle avoidance doesn’t provide protection for lateral movement on the sides of the drone when orbiting objects. Eg. DJI Mini 3 Pro
- Omni-Directional Obstacle Avoidance: Omni-directional normally means “all directions” but this isn’t true for drone obstacle avoidance. Omni-directional obstacle avoidance for drones is 360 degrees in the lateral field, upward and downward facing vision systems. The obstacle avoidance range comes close to encompassing the whole drone E.g. Mavic 3 Classic
Which DJI drones have obstacle avoidance?
Most DJI drones have some level of obstacle avoidance with the exception of cheaper models such as the Mini SE and toy drones such as the Tello.
Below are the current DJI drones with obstacle avoidance in order of increasing price:
DJI Mini 3 Pro
The Mini SE and Mini 2 have a downward sensor but aren’t considered to have obstacle avoidance, however, the Mini 3 Pro has tri-directional obstacle avoidance; forward, backward and underneath.
I rate the Mini 3 as one of the best drones with obstacle avoidance for the following reasons:
- Tri-directional obstacle avoidance
- The forward sensors have a much wider range with a width of 106 degrees
- Professional level features packed into a drone that is light enough to not be registered (when flown for fun only). To see why the Mini 3 Pro is so impressive check out DJI Mini SE vs Mini 2 vs Mini 3 Pro: What you need to know.
DJI Air Series
The Mavic Air and Mavic Air 2 are no longer in production but the Air 2S has an infrared sensing system and forward, upward, rear and downward vision system.
DJI FPV Series
The FPV drone is equipped with an infrared sensing system and forward, upward, downward vision system.
DJI Avatar Series
The DJI Avatar drone has two 3D infrared modules and two downward vision systems.
DJI Mavic Series : The Best Drone with Obstacle Avoidance
The DJI Mavic Pro has just forward and bottom sensors but the Mavic 3 Classic has onmidirectional obstacle avoidance.
DJI Mavic Pro: Bi-Directional Obstacle Avoidance
DJI Mavic 3 Classic: Onmi-Directional Obstacle Avoidance
The Mavic 3 Classic is one of very few drones that have almost complete sensor coverage for obstacle avoidance but is far from the most expensive. This is a professional level drone with an awesome 4/3″ camera lense that takes very impressive photos and video.
The DJI Mavic 3 is also the top in it’s field when it comes to long range drones, with an impressive distance of 15km. This is far more range than your ever need given the regulations on flying a drone within your visual line of site.
DJI Phantom Series
Both the Phantom 4 Pro and the Phantom 4 Pro 2.0 have forward, backward, side and bottom sensors.
NOTE: In P mode both forward and backward vision systems work but at speeds greater than 22kph only the vision system in the direction of travel works.
DJI Inspire Series
The Inspire 2 drone has vision systems front and bottom (stereo vision sensors), two ultrasonic sensors, two infrared modules on top. The infrared sensors are only active during certain flight modes.
As one of DJI’s more expensive drones, this is a good example that complete obstacle avoidance isn’t a premium feature. It’s nice to have but doesn’t replace good drone piloting skills.
Is obstacle avoidance on a drone worth it?
If your buying your first drone and weighing up if it’s worth paying more for a drone that has obstacle avoidance I’d suggest actually going for a more affordable drone like the Mini 2 and practice your piloting skills with prop guards attached. This has better transmission than most other cheap drones (Occusync 2 as compared to wifi). Obstacle avoidance isn’t a ‘fail safe’ and you’re going to crash your drone a few times while learning so it’s better to do this with a $500 drone than a $1000 drone.
If you decide to upgrade to something with a better quality camera and obstacle avoidance, the Mini 2 is very popular and can be sold second hand easily.
