Surveying a Site for Robot Mowers: Slopes, Wet Turf, Obstacles

Can a robot mower cut an open lawn without constant help?

Often yes, but only after someone has walked the ground with a plan. An open lawn with moderate slopes, firm turf that drains well, and few low fixtures can usually run a robot mower with little intervention. Slope, wet ground, sprinkler heads, bollards and drain grates decide how much of the rest holds up.

The survey sorts a site into three piles: turf the robot can cut alone, turf that needs wire fencing or an island, and ground the crew keeps. Few sites come out with only one pile. The sooner you know the split, the less time a crew lead spends pulling a stuck mower off a bank.

What slope rating should you measure against?

Manufacturers publish slope limits, but each figure is the maker's own, and our search found no standardized test behind them. The figures below come from search summaries taken on November 5, 2026, so check them against each maker's spec sheet before you commit. Husqvarna lists the Automower 535 AWD EPOS at 70% inside the installation and 50% at the boundary wire. Gardena's commercial reference sheet lists the Sileno at 35% inside and 15% at the boundary.

Read the boundary figure as the one that governs where wire can run. Husqvarna advises against running boundary wire across slopes steeper than 15%, with exceptions for some models. A strong interior number tells you little about where the wire can safely lie.

Percent and degrees are not interchangeable. An FJ Dynamics blog states that a 40% slope is roughly 18 degrees, so convert before setting a rating beside an angle finder reading. Measure across the full length of the bank rather than at one spot, since a short high point can mislead.

Log these for every slope zone:

• Interior slope and the direction the ground falls
• Boundary slope where the wire would run
• Length of the bank in meters
• Grass height, and whether the bank is wet on survey day

How does wet ground change the survey?

Wet ground is where slope ratings stop telling the whole story. A Yard Force installation manual warns that higher downhill speed can carry a mower over the boundary wire, especially on wet and slippery ground. We did not measure that effect, so read it as a manual warning, not a field rate.

Survey wet ground on a rainy day or just after irrigation if you can. Mark low spots that hold water, irrigation runoff paths, and any bank that turns slick. Keep the wire off the steepest edge, where a slide could carry the mower across it, and plan crew cover for those patches on wet days.

We have no verified figures on how often crews step in on wet turf. Set your own baseline during the first weeks of running, and compare it with the map rather than with someone else's anecdote.

Which obstacles need an island or wire fence?

Low, rigid fixtures are the usual concern. One installation manual in our search says to keep wire about 10 cm from obstacles under 1 cm high. A manual in the same family says ultrasonic or collision sensors on several models react only to objects above roughly 100 mm, so anything lower needs a wire fence or island rather than trust in the sensor.

Exposed roots near the surface belong outside the mowing area. Sprinkler heads are the gap in our research. None of the sources we checked addressed them directly, though the usual manual approach is an island around each head. Bollards and drain grates had no verified figures this run, so map them precisely and confirm the treatment with the maker before you commit.

Each island adds wire and survey time, so cluster sprinkler heads where the layout allows and count them on the sketch first.

How does a crew lead run the walk?

Sketch before you set a single stake. Husqvarna's installation guidance starts with a site sketch that marks every obstacle, the ideal charging station location, and the planned wire route. Walk the site in this order:

• Draw the boundary, buildings, walks and drives to scale, then outline the mowing area.
• Mark every sprinkler head, bollard, drain grate, tree root and utility box.
• Run the slope check and record each bank as described above.
• Flag wet and irrigation affected turf, and choose a charging station spot with power access.
• Mow the area before laying wire, because Husqvarna advises that grass can lift the wire.

Which areas should the crew keep for itself?

Keep the ground the robot cannot read or cannot hold. In practice that means steep banks past the boundary limit, wet low spots prone to sliding, clusters of sprinkler heads that would need many islands, drain grate fields, and bollard groups where the mower path becomes a tangle of turns.

Robomow's guide places the wire about 35 cm from walls and tall stones. That is a single brand's figure, so treat it as a starting point and confirm it with the maker you choose. The same guide notes that obstacles inside the mowing area also need boundary wire.

Put those zones on a written map the crew can read. That keeps the robot schedule and the human schedule from competing for the same grass. Hours the crew spends on banks and edges are the work the survey is meant to direct, not evidence that the plan failed.

What happens to the survey after it is done?

Service Robot Co. runs this kind of survey as the first step of a lease. We are an OEM neutral integrator, so we select robots across manufacturers for the site, then quote a three year lease with one fixed lease payment after a site assessment. Our nationwide US engineer network then handles deployment, integration, training and service, so one partner holds the map, the schedule and the repair call.

Whichever vendor you talk to, ask them to place the boundary figures on your sketch before a quote. A slope number that cannot be drawn on the map does not help a crew lead decide which grass to keep.