How Do Robot Vacuums Map Your Home? (2024)

tech Feb. 12, 2024

By Jordan McMahon, a technology and gadgets writer at the Strategist. He’s been covering technology since 2017 and previously wrote for Wired, Wirecutter, and Reviewed.com.

Photo-Illustration: The Strategist; Photo Getty

They all use sensors

At a base level, all robot vacuums use some combination of sensors to figure out where it is on the floor and whether it’s going to run into something. A combination of obstacle, wall, and cliff sensors (the same sensor that’s at the bottom of a computer mouse) tell the robot when it’s going to or has hit something, how close it is to a wall, or when it’s about to fall off an edge. These sensor-based robot vacuums may also have gyroscopes and accelerometers to calculate distances and figure out their direction. Lower-end models — like the Eufy Clean 11S or ILIFE V3s Pro —rely on sensors exclusively to get around. That’s how they produce random patterns to navigate the floor, with the goal of covering all of the square footage,though these models won’t be able to tell what room they’re in or where they’re going.

Some use more complex systems with confusing acronyms

Higher-end robot vacuums, like the iRobot Roomba Combo j9+ and the Ecovacs Deebot X2 Omni, usually have some combination of sensors. But they’re also equipped with more intelligent detection that helps the robot map your home more accurately. The most common of these systems are lidar (light detection and ranging) and VSLAM (visual simultaneous localization and mapping), and though the end result is similar, they are very different mechanisms. This is where things get a little bit more complicated.

What is the difference between lidar and VSLAM?

Lidar uses lasers to detect objects and surfaces in your home. Then, the robot uses that information to make a plan for how to best clean the detected area. Once it’s mapped out the area of a room, plus all the objects in the room (tables, chairs, dog toys), it can start its run, which usually consists of straight lines back and forth. Lidar works well in low-light, so you can run your vacuum when you’re not home without needing to keep the lights on. Lidar-based vacuums may retain and send some information to the company’s servers, such as a basic blueprint or the robot’s status. In those cases, the information that’s synced is encrypted to ensure no personally identifiable information is exposed.

VSLAM uses cameras to map out your rooms and identify obstructions. Like lidar, it uses information from the camera to create a blueprint of your home, so the robot can effectively plan its route. Because it basically has eyes, robot vacuums with VSLAM usually need to be run in the daytime or with the lights on, though there are some camera-based robot vacs that might use built-in lights to allow them to run in the dark. But the camera means it’s really effective at identifying stray objects in your home, and it stores that information to create better cleaning plans moving forward. It also helps your robot vacuum keep track of where it is in your home, by capturing details from your house, such as a corner of a picture frame or the edge of a door.

Does that mean my robot vacuum is spying on me?

I asked that question to Chris Jones, chief technology officer at iRobot. They use VSLAM technology in their models like the Roomba j7+ and j9+. The robot is able to figure out that it’s in your living room without having a complete picture of it, based on tiny details. Images of these constellations (which don’t leave your robot) are as unidentifiable as possible, Jones told me — they’re just pictures of that particular edge, corner, or surface, cropping out as much as possible while still being recognizable. You can also opt in to send iRobot encrypted images of obstacles it finds during cleaning jobs, to help improve its recognition software, but that won’t happen without your consent, and they’re deleted after 30 days.

Because they’re capturing actual images of your home, the thought of a robot zooming across your home and recording you can sound creepy. That said, it’s not actually recording you. Companies like iRobot go to great lengths to ensure nothing gets sent to them without your consent, and anything that does get sent is stripped of personally identifiable information, including any photos with a human in them. But just like with a blueprint produced by a lidar-based vacuum, a barebones blueprint of your home stripped of any personally identifying information may be sent to a company’s server strictly to sync the map between your robots. Most robot vacuum makers also have you either opt in or out of sending your information to them, and it’s always a good idea to find out how much information you’re giving up.

What if I really just want to stay off the grid?

Robot vacuums with strictly sensor-based navigation don’t have any cameras or microphones that could record sensitive personal data, so if you’re willing to deal with a less efficient cleaner in exchange for more privacy, I’d suggest a robot vacuum without VSLAM or lidar, like the ILIFE V3s Pro, TP-Link Tapo RV10 Plus, or Eufy Clean 11S. But if you want the most accurate robot possible, you’ll need to splurge on one with good VSLAM capabilities, like iRobot’s Roomba j9+, or a powerful lidar model like the Ecovacs Deebot T20 Omni.

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