Technology
Line-marking robots: what they change, and what they do not
GPS line-marking robots are on athletic fields and marketed for courts: what they get right, what a tape and a crew still do, and when we expect to use one.
Carl J. Gedeon, president, Industrial Surface
The newest tool in court work is a plastic box the size of a lawn mower that drives itself around a pad and draws a tennis court. I have watched one work on a field, I have priced one, and I have opinions. This article is about what GPS line-marking robots do, what they get right, what they do not change, and why our lines are still hand taped and hand painted this season.
What it is
A line-marking robot is a small four-wheeled vehicle with a paint tank, a spray nozzle, and a GPS receiver that uses a base station or a correction service to know where it is to within a fraction of an inch. You pick a court layout in a tablet app, tennis, pickleball, basketball, or a blended combination, set two reference points on the pad, and the robot drives the layout and sprays the lines. The two makes most contractors see are Turf Tank and TinyMobileRobots, both from Denmark, both built first for painting soccer and football fields, where they have replaced string lines and crews on thousands of grounds.
What it gets right
Accuracy, repeatably, without a crew. A court laid out by tape depends on the people holding the tape: a 78-foot measurement pulled hard, in the wind, by two people who have done it for years, is accurate to a quarter inch; done by two who have not, it is not. The robot's layout is the drawing, every time. For a pad with four pickleball courts and a tennis court sharing lines, where there are a few hundred measurements and every one has to agree with the others, that consistency is real.
Speed, on fields. On grass, the robot paints the lines directly, and a field that took three people a morning takes one person an hour. That is the economics the robots were built on.
What it does not change on a court
On a hard court the lines are not sprayed onto grass; they are taped and painted in two coats of textured acrylic, with the tape pulled while the paint is tacky so the edge is sharp. The robot can mark the layout, a chalk or paint guide, and the crew still tapes and paints along it. So on a court the robot replaces the tape-and-string layout hour, not the painting day. Useful; not transformative.
It also does not know what it is standing on. A court that is out of square, a fence that was set a foot off, a net post footing that is where it is: the robot draws the drawing, and a person has to decide where the drawing goes on the actual pad. That decision is the layout. The tape measure was never the hard part.
Where it will matter
Multi-sport layouts and new construction. When a pad is getting tennis, four pickleball courts and kids' lines in three colors, the robot's layout is faster and surer than three sets of string lines, and the app will show the owner the result before anyone paints. On a new pad, marking the fence line, the net footings and the court on bare asphalt in one pass is a morning saved. For a single tennis court resurfacing, where the old lines are still faintly there and the net posts fix the geometry, the robot adds a setup hour to a job that did not need it.
What it costs
Tens of thousands of dollars for the machine, plus a subscription for the positioning correction, which is why the first owners are the big field-painting contractors and the school districts with a dozen fields to line every week. A court contractor doing a few dozen courts a year does the arithmetic differently; renting one for the big layouts is where most of us will start.
Our position, honestly
Our lines are hand taped and hand painted, and our layouts are done from the net line with a long tape and the diagonals checked, which is how every court we have built since 1957 was done and how the USTA diagram expects it to be done. A court whose diagonals match is square. I expect we will put a robot on the big multi-sport pads within a few seasons, because the layouts are getting more complicated every year and the consistency is worth something. I do not expect it to change what you see on the court, because the paint, the tape and the person pulling it are what you see, and those are not being replaced by anything.