Solar Array Mowing: Row Spacing and Satellite Robot Passes

Can a robot mower cut between solar rows without losing its position?

Usually, but only where the mower can see enough open sky to hold a satellite fix. On a utility scale or community solar site, that depends less on the mower's make than on the geometry of the array. Elevated rows, fence lines and equipment pads all narrow the view a receiver has of the sky, and each one shrinks the margin.

For a grounds crew, the practical answer is to treat row spacing, post height and fence location as part of the mowing approach. Map those limits before the first pass, then test the route where the sky is most restricted. The sections below explain why, and what the published evidence does and does not support.

Why row spacing and post height matter for satellite guidance

Blockage under elevated arrays is a known problem. Vendor and glossary sources warn that trees, walls, metal roofs, parked vehicles and retaining walls can block satellite signals or reflect them before they reach the antenna. Reflections matter because a reflective surface can cause sudden positional jumps through multipath.

Commercial evidence is more useful than theory. Xsens describes a case in which an iKnowHow Aristos mower worked at an Enel site in Greece. The mower carries an Xsens RTK GNSS and inertial module to keep tracking when the satellite signal drops, follows an operator mapped route, and uses a charging station that hosts an RTK beacon.

Xsens reports positioning of about plus or minus 5 cm, and says that holds only with a clear GNSS signal and RTK corrections. The same case notes that the mower had to sit low enough to cut under panels as well as between them. Clearance and row gap are one design question, not two.

No published row spacing threshold for RTK reliability turned up in this review. A hobbyist forum thread describes roughly 30 cm between panel rows and about 25 cm of ground clearance, and users there doubted that RTK would hold under the panels. That report is anecdotal and unmeasured, but its advice stands: test RTK and magnetometer performance on site before committing.

How fence lines and equipment pads change the sky view

When obstacles block satellites or correction data, accuracy drops, and the receiver can fall from a fixed solution to a float or degraded state. A mower that keeps moving does not announce that change. It simply cuts less precisely until a crew notices the stripes or the edge.

Reference stations need open sky too. Mammotion, which sells robotic mowers and RTK reference stations, says its Luba mower and reference station need at least a 90 degree open sky view for reliable signal, and advises keeping boundaries away from high trees or walls. That is vendor guidance, useful as a starting threshold for a site survey rather than as a standard.

Fence lines and equipment pads deserve the same scrutiny. A reference receiver can be blocked as well as the mower, and both local RTK and network RTK can be affected by obstruction. A pad that looks open from the ground may still cut the sky along one side of its footprint.

Vendors also describe fallbacks. Camera based visual SLAM can use lawn edges, trees, walls and fixed features, and an inertial unit can hold a path briefly without RTK. Both help during short blackouts. Neither removes the need to design lanes around narrow sky.

Mapping access lanes before the first pass

Start by treating the array as a set of lanes. Walk each row gap, note post height and mark where the sky closes in. Then decide which gaps the robot takes and which go to a crew with a trimmer, since the robot will not handle every transition well.

Repeat runs matter more than a single clean pass. Test routes beside each obstruction and compare the spread of positions with a run in an open area. If the spread near a fence run is far wider than in the open, that lane needs another approach or a crew.

Build the lane map around a few checks.

• Record open sky in a clear area, then compare each post line and fence run against that baseline.
• Mark hold points where the path enters a narrow gap, so the mower slows or stops before the signal thins.
• Note where the charging station sits relative to the RTK beacon, since the Xsens case placed the beacon there.
• Repeat the check after vegetation grows or new equipment goes in, because new obstacles change the sky.

Checking the edges around equipment pads and fence lines

The edge is where a robot's confidence and a crew's judgment meet. Inverter skids, fence posts and equipment pads create corners that a satellite fix cannot see around, and where clutter can confuse the camera. Walk each pad perimeter before the season opens, and again after any site change.

A Vinnova funded European project on a 30 hectare solar park reported that more work was needed before full autonomous operation, including mowing near obstacles and under panels, and recharging. The robot repeats a known route well. Its weakest moments are the transitions the crew understands best.

Swap Robotics maps each site first, then runs routes with remote oversight. Its vendor claims cuts of about two to eight inches. Crews should set a target height for each zone rather than accept a default, and inspect the strip left beside each pad after the first run.

What the vendor numbers do and do not prove

Some figures help a proposal, and some only frame a question. Renu Robotics, which makes an electric autonomous mower that works between panel rows, reports cutting client vegetation management costs by 30 to 50 percent. Digi's customer story presents that as vendor reported and not independently verified, so treat it as a claim to test on your own site.

Clearance figures need the same care. Swap Robotics claims its units can cut beneath an array raised at least 18 inches off the ground. Solar Power World reported in October 2022 on SOLV Energy's work with Swap Robotics. That coverage explains the relationship, but it does not give field measurements for your rows.

The rule for any figure is the same. Ask what the number was measured on, under what sky, and by whom. A plus or minus 5 cm result from one commercial case tells you what a clear GNSS signal can deliver, not what a particular row layout will deliver.

Where Service Robot Co. fits in a solar grounds program

Service Robot Co. is an OEM neutral integrator for US businesses. We compare mowers across manufacturers against the sky view, slope and edge conditions of a specific array, then lease the chosen units on a three year lease with one fixed lease payment quoted after a site assessment. We deploy the units, train crews, and service every robot under RoboCare, backed by regional service engineers in the states we serve.

On a solar site, a mower stopped at a fence line needs a fast answer more than a long explanation. One service path for the whole fleet keeps the crew from chasing several vendors when a unit goes quiet.