What Are Downward Vision Sensors in Drones? (Explained for Beginners)

Drone technology continues to evolve at a rapid rate, advancing the capabilities of these devices.

One area where drone tech has progressed to an especially impressive degree is downward vision sensors.

What exactly are downward vision sensors, and how do they work in drones?

Downward vision sensors are bottom-facing, often infrared sensors that gauge the drone’s distance from the ground and help it avoid obstacles. They’re useful for low-light and indoor flights or in other scenarios with less reliable GPS.

This guide to downward vision sensors will explain them thoroughly, including guidance on their range, functionality, and whether you can disable your sensors.

What are downward vision sensors in drones? (In detail) #

Downward vision sensors are one of several types found in many drones.

They’re sometimes part of a multi-directional obstacle avoidance system but might be used individually depending on the drone model.

As the name implies, these sensors are installed underneath the drone to read what’s happening below it.

Pilots must stay at a recommended altitude for the vision sensors to work optimally. If they fly higher than the range or lower, the sensors cannot necessarily perceive all obstacles.

Most downward vision sensors are infrared, meaning they’re sensitive to specific wavelengths. Infrared sensors have become the standard in many areas of technology, including motion detectors.

Infrared sensors often come in pairs, with one generating a light that reflects into the other.

The downward vision sensors will typically not illuminate, so pilots must know where they are on their drones and keep them clean.

Downward vision sensors often require calibration, especially when you first use your drone out of the box. If you purchase a used drone, you should also calibrate the vision sensors before flying.

Another scenario where you may have to calibrate or recalibrate the vision sensors is after a period of nonuse.

While downward vision sensors in drones have come a long way, and the technology continues to evolve with new models (especially from leading drone pioneers such as DJI and Autel), these sensors have some limitations.

They work best in low-light conditions, including those indoors and outdoors. However, there’s a fine line to be treaded between low light and no light.

If the environment is under 10 lux, you should think twice before flying, as the downward vision sensors can be rendered ineffective.

» MORE: Can You Fly the DJI Mini 2 SE at Night? (Explained for Beginners)

Likewise, the sensors experience limitations in very bright conditions over 40,000 lux.

Flying a drone in areas lacking pattern variations can also cause the downward vision sensors to fail or work less effectively.

That makes using a drone with downward vision sensors dangerous in the following scenarios:

• In areas where the obstacles are small, like in a tree-lined forest with many branches
• In areas where the texture or pattern repeats, such as a wallpapered or tiled wall
• In areas where obstacles have no texture or identifiable pattern, like a power pole
• In areas where infrared waves are absorbed or reflected, such as mirrored walls
• In areas where the light changes drastically and often
• In areas where the objects or surfaces move
• In areas where the surface is translucent, like water
• In areas where the surface is reflective
• In areas where the environment is monochrome

What is the range of downward vision sensors? #

Another instance in which downward vision sensors will not work properly is if they’re used outside of range.

The sensors can only gauge the distance from the ground when the drone stays at a certain altitude.

That altitude range can vary by model, but generally, the sensors become ineffective if a drone exceeds 11 meters in altitude.

The precision range is between 0.5 and 11 meters, and the detectable range is 11 to 22 meters.

That said, always consult your drone manual for the downward vision sensor range for your particular drone make and model.

» MORE: What Is a Gimbal in Drones? (Explained for Beginners)

Do all drones have downward vision sensors? #

The more features a drone has, especially technologically advanced ones like vision and obstacle avoidance sensors, the more it costs.

Drones are available at all price points for different audiences, from kids to older first-time pilots and seasoned professionals.

That’s why every drone does not include downward vision sensors.

Cheap toy drones often lack any sensors to keep the price affordable. These entry-level drones are available for as little as $20 or $30.

They’re also designed for play with the expectation that they will get beat up, as inexperienced pilots often make mistakes and crash.

Equipping toy drones with sensors would be a waste of money for the manufacturer.

Mid-level drones between $50 and $100 are better candidates for a downward vision system, but even still, there are no guarantees. Heck, even some DJI drones lack full obstacle sensing, so you can’t expect it out of every drone you see.

Costlier drones that are $200 to $500 and up are likelier to have downward vision sensors, and more expensive drones in the $1,000 range should have an advanced vision-detecting system.

The exception is FPV drones, as many lack any type of obstacle avoidance system.

**» MORE: ** FPV Drones vs. Regular Drones (Explained for Beginners)

How many downward vision sensors does a drone need for proper functionality? #

Drone sensors come in all types, including heat, chemical, magnetic, image, sound, and light sensors such as GPS sensors, barometers, magnetometers, and accelerometers.

The sensor’s makeup determines how many are appropriate for a drone.

Considering that most downward vision sensors are infrared, these work best with at least two sensors to reflect the light from one to another.

» MORE: How to Calibrate a Drone (Ultimate Guide)

Can a drone hover with only downward vision sensors and no GPS? #

Downward vision sensors work in situations where a drone’s GPS doesn’t, such as indoors or in other enclosed environments.

In those scenarios, the drone will rely on the sensors to hover in place and fly without colliding with obstacles.

Although flying without GPS can seem a scary proposition, a downward vision system is a useful backup pilots can rely on to guide their drones safely back to them.

However, the drone must remain at the prescribed altitude for the sensors to continue working.

» MORE: Can Drones Use Ground Penetrating Radar? (Explained)

Can you disable the downward vision sensors of a drone? #

Perhaps you only fly in environments where your GPS works well, or your downward vision sensors have forced your drone to land if you’ve taken a tight turn.

You’d like to disable the sensors the next time you use your drone. Can you?

You have a few options. Third-party apps might allow you to disable the sensors. The most reliable way is to put a piece of masking tape or duct tape over the sensor.

You can also buy a drone that lacks downward vision sensors, although that can be expensive and inconvenient.  

The more important question here isn’t whether you can or can’t disable a drone’s downward vision sensors. It’s why would you want to?

Yes, it’s frustrating when the vision-sensing system doesn’t let you fly your drone how you wish.

That’s just like how pilots get frustrated with DJI’s geofencing system, which will automatically land your drone if you fly outside of its prescribed range.

These safety features exist for a reason. In the case of downward vision sensors, they’re installed in your drone to provide it with a greater field of vision.

They help your drone see what’s underneath it and can prevent crashes and collisions with obstacles.

**» MORE: **Drone Safety Features (All You Need to Know)

Sure, the downward vision sensors aren’t perfect. You can’t reliably use them over water, and they’re less useful in indoor environments with repeating patterns or no discernable patterns.

Even still, it’s better to have them than not. Taping your vision sensors or otherwise disabling them makes flying riskier.

If you crash your drone and it’s still covered under warranty, you might negate your replacement because you tampered with the drone.

You can also damage the sensors by taping them. Tape residue can stick on the sensor, and trying to scour it off can scratch the sensor.

Once that happens, it won’t function reliably, so you’ll again have to shell out to get it replaced.

You’re better off leaving it alone.

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