How robot lawn mowers navigate
The single biggest decision in a robot mower isn't the brand or the price — it's how it finds its way around your lawn. Four approaches dominate, and each suits a very different garden.
1. Boundary wire
A thin wire is pegged or buried around the lawn's perimeter (and around flowerbeds or ponds). The mower senses the wire's signal and stays inside it, bouncing around in a semi-random pattern until the whole area is cut.
Strengths: the cheapest and most proven system, and the most weatherproof — it doesn't care about tree canopy, cloud or darkness. Trade-offs: installation is a one-time chore, and changing the lawn shape means moving wire. Wired models still hold the highest slope ratings on the market.
2. RTK-GPS (wire-free)
RTK ("real-time kinematic") GPS pairs the mower with a fixed reference antenna to reach centimetre-level accuracy — far beyond ordinary satnav. You drive the boundary once in an app, and the mower mows in tidy, efficient lanes.
Strengths: no wire, neat striped mowing, easy to re-map. Trade-offs: it needs a reasonably clear view of the sky. Dense tree canopy, tall buildings or narrow side-passages can disrupt the signal, though many models bridge short gaps with onboard sensors.
3. AI vision (wire-free)
Camera-based mowers read the lawn the way you do — distinguishing grass from path, bed and obstacle — and increasingly recognise objects and pets to avoid them.
Strengths: wire-free and unbothered by canopy that defeats GPS. Trade-offs: cameras want daylight and a visible contrast between lawn and edge; very overgrown or low-contrast boundaries are harder.
4. Sensor fusion (wire-free)
The most capable models combine RTK with vision (and sometimes LiDAR), so when one sense is weak the other compensates. This is what tackles large, sloped or partly-shaded gardens that defeat any single system.
Strengths: the most robust and flexible. Trade-offs: the most expensive, and overkill for a simple rectangular lawn.
Which should you choose?
As a rough guide: open-sky lawns suit RTK; tree-shaded lawns suit vision; large or complex gardens suit fusion; and budget-conscious or unusually awkward layouts are often best served by a proven wired model. But the honest answer depends on the specifics of your plot.
Rather than guess, answer five questions in our Robot Navigation Chooser — it recommends a technology and lists the catalogue robots that use it.
Once you know the technology, filter robot mowers by it, or read our pick of the best wire-free robot mowers.