Every robot mower has to answer one question before it cuts a single blade: where does the lawn end? There are two main answers. A boundary wire is a thin cable you lay around the edge of the lawn. A wire-free mower uses satellite positioning, usually RTK GPS, and a map you draw in an app.
Both work. They fail in different ways, so the right choice depends on your yard rather than on which one sounds newer.
How a boundary wire mower works
You peg or bury a low-voltage wire around the edge of the lawn and around anything the mower should avoid, such as garden beds or a tree base. The charging station sends a signal through the loop. The mower senses the wire and turns back when it reaches it.
Strengths:
- No satellite signal needed. Mammotion notes that wired mowers stay highly consistent, even in areas with dense tree cover or buildings.
- Lower upfront cost. The same source lists wired models as generally more affordable than wireless ones.
- Predictable edges. The boundary is a physical line that does not drift.
Weaknesses:
- Installation takes time. You walk the whole perimeter, peg the wire and route it around every obstacle.
- The wire can break. Mammotion lists pets, weather and garden tools as common causes. A single break stops the mower until you find and splice it.
- Changing the layout means moving the wire. A new garden bed means new wire.
In rainy climates, erosion can expose shallow wire. Our sloped yard setup guide covers burying and routing wire on hillsides.
How a wire-free (RTK GPS) mower works
Standard GPS is accurate to a few meters, which is not precise enough to keep a mower out of a flower bed. RTK (real-time kinematic) GPS adds a fixed reference station near your home that corrects the satellite signal. You then walk or drive the mower around the edge once in the app to record the boundary. No-go zones are drawn on the map.
Strengths:
- No wire to install or repair. Nothing to cut with an edger and nothing for rain to expose.
- Easy layout changes. Edit the map in the app instead of digging. Mammotion lists greater flexibility for lawn modifications without needing rewiring.
- Multiple zones. Separate front and back lawns can be handled as separate areas on one map.
Weaknesses:
- It needs open sky. Performance depends on stable satellite signals, which can be affected by trees, walls, or bad weather. Dense canopy, tall walls and narrow side yards between houses are the usual trouble spots.
- Higher upfront cost. RTK hardware adds to the price.
- Firmware and recalibration. Expect app updates and the occasional re-survey of the boundary.
Hybrid: GPS plus boundary wire
Some mowers combine both. The wire defines the edge, and GPS helps the mower plan its route and track which areas it has already covered. You still install wire, but navigation inside the boundary is more systematic than random bouncing.
How to decide: five questions about your yard
- How much open sky does the lawn have? Mostly open: wire-free works well. Heavy tree canopy, tall walls or tight side yards: wire is safer.
- How often does the layout change? If you add beds, move play sets or rotate garden areas, wire-free saves rework.
- How big is the lawn? Larger lawns mean more wire to lay and more places for it to break. That makes wire-free more attractive as size grows.
- What is under the turf? Rocky ground makes pegging wire harder. Soil that washes out in heavy rain can expose it.
- How much setup work will you do? Wire is a one-time weekend job, then occasional repairs. RTK setup happens in the app, but you need a good spot for the reference station.
Rule of thumb: choose wire for dependable boundaries under trees and around buildings at a lower price. Choose RTK if your lawn is open, large, or changes often.
How the BoriBots mowers line up
All three mowers below come from the BoriBots catalog. The specs are taken from each product page.
| Mower | Boundary system | Rated lawn size | Slope handling | Cutting |
|---|---|---|---|---|
| TerraBOT Edge | Boundary wire | Up to 0.25 acre | Not listed | Height 1.0–3.0 in |
| TerraBot Mow X | GPS + boundary wire | Up to 1/2 acre | Up to 35% grade | 9.5 in width, height 1.2–3.5 in |
| TerraBOT Max | RTK-GPS, no wire needed | Up to 1 acre | Up to 45% grade | 12 in width, built-in mulching |
Matching them to yards:
- Small yard with garden beds and palms, up to a quarter acre: the TerraBOT Edge uses boundary wire, which suits a compact lawn with trees overhead. It also has a rain sensor and app scheduling.
- Mid-size lawn up to half an acre: the TerraBot Mow X pairs GPS guidance with boundary wire and lists 35% slope handling, a 58dB noise level and an anti-theft PIN lock.
- Large, open property up to a full acre: the TerraBOT Max uses RTK-GPS mapping with no buried wire, handles up to 45% grade, and mulches clippings back into the lawn.
If your yard is large but heavily shaded, a wired or hybrid model is the safer choice even though wire-free is more convenient. When in doubt, check your satellite reception at the edges of the lawn with a phone GPS app before you buy.
For grass type, cutting height and climate, see our robot lawn mower buying guide for tropical grass, or compare every model on the lawn robots page.
Frequently Asked Questions
Quick answers to common questions about this topic.
Not always. Wire-free RTK mowers are easier to set up and change, but they need a stable satellite signal. Boundary wire mowers work under trees and near buildings and usually cost less, but the wire takes time to install and can break.
They can struggle. Trees, walls and bad weather can interfere with the satellite signal and cause missed areas. Lawns with heavy canopy are usually better served by a boundary wire or hybrid mower.
The mower stops and reports a signal fault. You find the break, splice the wire with a waterproof connector, and restart. Burying the wire deeper helps prevent breaks from edging tools and erosion.
The TerraBOT Max uses RTK-GPS mapping and needs no buried wire. The TerraBOT Edge uses boundary wire, and the TerraBot Mow X combines GPS with boundary wire.
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