Robot lawn mowers of yore started off using a boundary wire to determine where it could and could not go, and they were problematic. The boundary wire had to make a complete, unbroken circle. And if anything happened to the wire, you had problems. These days, robot mowers work via GPS, but it's GPS with a little bit extra in an RTK beacon. Scott Porteous, head of robotics for Husqvarna broke it down for me.
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GPS navigation
GPS today is accurate down to a few feet. That's fine when you're navigating in your car, or looking for Tupperware in the woods, but it's not good for things like property lines. The Real-Time Kinematic beacon also communicates with GPS satellites to provide a fixed location on Earth that the satellites know about. In essence, the RTK beacon tells the satellites, "I'm always here." Meanwhile, the mower drives around, and the beacon tells the mower that the satellites think it's 5 feet to the north, so the mower should take the location that GPS is reading and adjust it accordingly. This allows robot mowers to get accuracy down to the centimeter.
GPS coverage
Another thing to consider is your general GPS coverage. If you live out in the suburbs, there's a good chance you'll be able to find a spot in your yard to set up a base station and RTK beacon. If you live in the city, that might be challenging. Also, wherever you set up your mower, you'll probably need to be within Wi-Fi range for the mower to operate properly. A mower like the Yarbo actually gets an ethernet cable that runs to a router. If you decide to go with the Yarbo, that's something you'll need to do.
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Cutting width
Robot mowers have a lot of difficulty with narrow paths. The reason for this is due to those blades and its overall construction. For example, the Segway mower's chassis is 20.5 inches with a cutting width of 9 inches. The Sunseeker, one of the smaller bots, has a 14-inch width accompanied by a cutting width of 8 inches. This is not conducive to cutting narrow paths. Even if the body of the mower fits there, it can't get the right angle to cut all the grass. Mostly, they just wiggle back and forth, which doesn't do a heck of a lot.
Camera systems
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