AB Line Guidance – Drive Straight Parallel Passes With Just Your iPhone
AB line guidance is the foundation of precision agriculture — it's how tractors, sprayers, and seeders drive perfectly straight, evenly spaced passes across a field without expensive console hardware. Tractor GPS brings this same AB line technology to your iPhone or iPad, so you get agronomy-grade straight-line guidance for the cost of an app instead of a $2,000+ guidance console.
How AB Line Guidance Works
1. Set your implement width
Before you start a pass, enter your implement's working width — a 12m sprayer, 6m seeder, or 24m spreader. This number is what Tractor GPS uses to calculate every parallel track across the field.
2. Set point A
Drive to the edge of your field where you want your first pass to begin. Tap Set A. This marks the starting point of your reference line.
3. Drive your first pass and set point B
Drive straight for at least 20 meters along your intended line, then tap Set B. Tractor GPS now has your reference heading — the AB line.
4. Follow the lightbar across the whole field
Once your AB line is set, the app automatically projects parallel guidance tracks across your entire field, spaced exactly to your implement width. A responsive on-screen lightbar shows you exactly how far left or right you are from the line, so you can correct instantly and hold a straight pass — even on long runs, in low light, or when operator fatigue sets in.
Why AB Line Guidance Matters
- No overlap, no gaps — consistent spacing means you never double-spray or double-fertilize, and you never miss a strip
- Save fuel and inputs — eliminating overlap directly cuts diesel, chemical, and seed costs on every pass
- Works with any implement — sprayers, seeders, spreaders, mowers, tillage equipment
- Sub-meter accuracy — modern iPhone multi-frequency GPS delivers roughly 30–50cm pass-to-pass accuracy under clear sky
- 100% offline — AB line guidance runs on satellite GNSS (GPS, Galileo, GLONASS) directly, with zero need for cellular signal in remote fields
AB Line vs Curved Line vs A+ Line
Tractor GPS supports straight AB lines for rectangular and regular-shaped fields. For irregular boundaries, curved-line and free-mode tracking are also available so your guidance track follows the actual contour of the field instead of a straight projection.
Compatible With Every Tractor Brand
Because AB line guidance runs entirely on your iPhone's GPS, it works independently of your tractor's make or model — John Deere, Case IH, New Holland, Kubota, Massey Ferguson, Mahindra, Fendt, CLAAS, Deutz-Fahr, and Yanmar are all fully supported.
Frequently Asked Questions
How accurate is AB line guidance on an iPhone?
Under clear sky conditions, modern iPhone multi-frequency GPS delivers around 30–50cm pass-to-pass accuracy — precise enough for spraying, fertilizer spreading, mowing, and tillage passes.
Do I need an external GPS antenna for AB line guidance?
No. Tractor GPS uses your iPhone or iPad's built-in GPS receiver. An external Bluetooth RTK receiver is supported as an optional upgrade for centimeter-level accuracy, but it isn't required to get started.
Does AB line guidance work without internet?
Yes. AB line guidance computes entirely from satellite GNSS signals and works 100% offline, so it's fully usable in remote fields with zero cellular coverage.
How do I reset or change my AB line mid-field?
Simply tap Set A again at any point to start a new reference line — useful if your field has multiple sections with different pass directions.