How tractor GPS works on a phone
Short answer
Tractor GPS – Field Guidance uses the GPS already in your iPhone or iPad to draw straight guidance lines across a field, spaced at your implement's working width. You steer; the screen shows how far you are off the line and paints the ground you have covered.
Updated · Oran Dynamics
What happens, step by step
- The phone finds its position. The app reads the location iOS provides, about once a second from the phone's own GPS (or from an external receiver paired in iOS). The app smooths it so the tractor marker moves continuously and the heading stays steady.
- You set a line. Drive to the start of a pass and tap A, drive along it and tap B. For a saved field, the app can also lay out the lines for you: best fit, parallel to any boundary edge, or at an angle you choose. See A-B lines and field lines and headlands.
- It draws the passes. Parallel lines are spaced at the working width of the implement you selected. Set the width right and each pass sits against the last. See working width and overlap.
- You steer to the line. A readout shows the distance to the nearest line, and left or right arrows change colour as you drift: white when you're within 10% of the implement width, yellow at 10–20%, orange beyond that.
- Coverage paints behind you. Worked ground fills in on the map in the implement's colour, so a missed strip shows up in the cab rather than in the crop a month later. See coverage mapping.
- The job is logged. Area covered, time, distance, average speed and the coverage map are saved to the work log, and you can continue the job later.
Good to know
- You stay in control. It guides; you steer.
- Accuracy depends on your phone. Phone GPS is a metre or two on newer dual-frequency iPhones, up to about 5 m on older ones. That suits wide-implement work like spreading, spraying and mowing, not planting rows. See how accurate a phone is, and our phone vs light bar vs autosteer vs RTK guide if you need more.
What you need
An iPhone, or a cellular iPad, running iOS 17 or later; a mount; and a charger. A Wi-Fi-only iPad has no GPS of its own but can take its position from an iPhone over GPS Relay. Details on the setup page.
- A-B line guidance on an iPhone What an A-B line is and how to set one in Tractor GPS – Field Guidance: tap A, drive, tap B, and the app draws parallel passes at your implement width. Set in two taps.
- Field guidelines and headlands For a saved field, Tractor GPS – Field Guidance can lay out the guidance lines for you: best fit, parallel to any boundary edge or a set angle, ranked by number of turns, with 0–10 headland lines.
- Coverage mapping: see what you've covered Tractor GPS – Field Guidance paints worked ground on the map as you drive, in each implement's colour. Area covered counts overlaps once, jobs can be paused and continued, and everything is logged.
- Working width and overlap Why working width matters for GPS guidance, how to set it and the implement offset in Tractor GPS – Field Guidance, and how much overlap costs. Includes a free overlap calculator.
- How accurate is a phone as tractor GPS? Measured against an RTK reference, a dual-frequency iPhone is typically within 0.5–0.7 m side-to-side under open sky; older iPhones are typically within 4.9 m (GPS.gov). Which iPhones are dual-frequency, what the app adds, and when you need RTK.
- Phone vs light bar vs autosteer vs RTK: tractor GPS options and costs What each kind of tractor GPS costs and how accurate it is, with sourced prices: phone apps (about $30–$100 a year), light bars ($1,500–$2,000), autosteer kits ($3,000–$12,000+) and RTK corrections.
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