Robot mower antennas and sky view

38 of the 65 robot mowers in the Botsize dataset steer by satellite positioning. This guide covers what they need from your garden: an antenna position, a correction service, and sky over the lawn.

Why the sky matters

A smartphone GPS is accurate to about 4.9 m (16 ft) under open sky. GPS.gov lists what makes it worse: signals blocked by buildings, bridges and trees, and signals reflected off buildings or walls (GPS.gov). A mower corrects its position with RTK to reach a few centimeters, but the correction only works while the receiver tracks enough satellites. Under dense canopy or close to a tall wall it tracks fewer satellites and picks up reflected signals, and the position can drift.

Your own antenna or a network

RTK needs a fixed reference with a known position. There are two ways to get one.

A reference station at home. An antenna on a short pole, a wall or a roof sends corrections to the mower. It needs power, open sky and a spot within range of the lawn.
Network RTK. The mower receives corrections from a network of stations over mobile data. No antenna goes up, but the mower needs mobile coverage. Data plans differ by maker: some include several years of data, others charge a yearly fee after a free period, so check the plan on the maker's page.

In the dataset, 5 satellite models need an antenna at home, 26 do not and 7 do not say. 33 support network RTK, some of them alongside an antenna in the box. The result card shows "antenna: not stated" when the maker is silent, and the model page lists network RTK where the maker states it.

Where the antenna goes

Makers publish placement rules in their support pages. Two of them, side by side:

Sunseeker asks for at least 100° of unobstructed sky above the antenna, at least 1.5 m (4.9 ft) from walls and trees, upright and not on a slope. In the northern hemisphere it asks you to keep the southern sky clear, in the southern hemisphere the northern sky (Sunseeker support).
Mammotion asks for open ground or an unobstructed wall or roof, with no roofs or trees over the station, close to the charging station. It warns against the corner of an L shaped building, a narrow path between two buildings and a spot under a tree. For U and O shaped lawns or several lawns it suggests a wall or roof mount (Mammotion support).

An antenna with 100° of open sky, clear of the wall and the tree.

Read the rules for the model you are considering before you buy. If no spot in the garden meets them, a roof or wall mount may, and a model with network RTK or a LiDAR model avoids the question.

The lawn needs sky too

A perfect antenna spot does not help a mower working under a big tree. Its own receiver needs the same sky. A satellite model that also carries a camera or LiDAR has a second sensor to work with. A satellite only model has nothing else to steer by.

Walk the lawn and mark the areas under canopy or within a few meters of a tall wall.
Estimate how much of the lawn they cover. A strip along a fence is a different problem from a lawn under one large oak.
Look at where the mower has to pass: a gap between the house and a garage can be the one spot where a satellite model loses its position.
After installation, the app of many satellite models shows the number of satellites and the signal strength. Mammotion names both in its station guide.

How the sizer treats sky

The mower sizer asks whether the lawn has open sky, some trees or buildings, or heavy cover. Models that steer by satellite positioning alone, with no camera, LiDAR or wire, get the warning "satellite positioning needs open sky" under heavy cover and a softer note under some trees or buildings. 4 models in the dataset are in that group. The warning never removes a model from the results: only you can judge your trees. Satellite models with a camera or LiDAR get no warning, but under heavy cover a note that satellite positioning works best under open sky. Models that steer by wire, camera or LiDAR alone get no sky note.

For a shaded lawn, compare the results on robot mowers for lawns under trees, and see boundary wire vs wire-free for the families that do not depend on the sky.

Questions about antennas and sky view

Can the antenna go on the roof?

Several makers allow a wall or roof mount and suggest it for lawns on more than one side of the house. Check the range to the far end of the lawn and the power supply in the maker's guide.

Does a satellite mower work under trees?

Scattered trees with gaps between them leave more sky than a closed canopy. Under dense canopy the position can drift. A satellite model that adds a camera or LiDAR has a second sensor, and a boundary wire or LiDAR model does not need the sky at all.

What is network RTK?

Corrections from a network of reference stations, received over mobile data instead of from an antenna in your garden. The mower still needs open sky to see the satellites.