I’ve been farming with my father in Jamestown, South Australia for years. Mixed operation — cropping and livestock. Like every broadacre farmer, I know the value of straight lines. And like every farmer who’s looked at the price tag on a proper guidance system, I’ve had that moment where you think: there has to be a cheaper way to do this.

The problem

Here’s the thing about GPS guidance in 2026: the technology itself isn’t expensive. GPS modules that can give you metre-level accuracy cost thirty dollars. The software to calculate cross-track error from a reference line is, computationally speaking, trivial. And yet a basic lightbar system from one of the big brands will set you back thousands. A full autosteer setup? Tens of thousands.

You’re not paying for the technology. You’re paying for the proprietary ecosystem — the locked-down hardware, the subscription services, the dealer network, the certification programs. All of which have value, but not everyone needs all of it. Sometimes you just want straight lines.

The spark

I’d been teaching myself to code for a while — Python first, then Rust when I wanted something faster and more reliable. I was building other tools for the farm (that’s a story for another post), and one day it clicked: I already know how GPS works. I already know what a lightbar needs to do. Why don’t I just build one?

So I ordered a Quectel LC29H DA GPS module off AliExpress for about thirty bucks. Plugged it into my laptop. Started parsing NMEA sentences. Within a weekend, I had a dot moving on a screen that matched my actual position in the paddock.

Within a month, I had a working lightbar.

What Finn Guidance does

The concept is deliberately simple. You have a laptop (any Windows laptop — the old one gathering dust in the office will do). You plug in a USB GPS module. You run the software. You set an A-B line by marking two points in the paddock. And then the lightbar shows you how far off-line you are, in real time.

That’s the core of it. But the details matter:

  • Auto-detection — plug in the GPS and the software finds it. No COM port configuration, no driver installs.
  • Position smoothing — the GPS updates at 1Hz, but the display interpolates between fixes so it doesn’t feel jerky.
  • Field management — save your A-B lines grouped by field. Load them next time. Export as JSON to transfer between machines.
  • Auto-pass selection — set your implement width and the software automatically snaps to the nearest pass line.
  • Nudge — offset the guidance line by a precise amount for inter-row sowing. This one came from a real need during our last seeding program.
  • Coverage logging — records where you’ve been, exportable as CSV.

What it costs

The software is free. Open source, no strings.

The hardware is a USB GPS module — roughly $30–40 depending on where you source it. We’ll be selling tested modules and complete starter kits through the shop soon, but you can also source your own.

Total cost: under fifty dollars and about five minutes of setup time.

What it doesn’t do (yet)

Let’s be honest about limitations. Finn Guidance is a lightbar, not an autosteer system. It tells you where to go — you still have to steer. With a standalone GPS module (no RTK corrections), accuracy is roughly 1–2 metres pass-to-pass. That’s fine for broadacre spreading, spraying, and basic seeding. It’s not fine for controlled traffic or precision planting.

RTK support is on the roadmap. When that lands, accuracy drops to about 2 centimetres, which opens up a whole new set of possibilities.

Why open source?

Because I’ve been on the receiving end of proprietary ag-tech that stops being supported, or gets acquired, or requires a subscription that keeps going up. Open source means the code is there for anyone to inspect, modify, or build on. If I get hit by a header tomorrow, the software doesn’t die with me.

It also means other developers — farmer-developers, uni students, tinkerers — can contribute. The best features will probably come from people solving problems I haven’t thought of yet.

What’s next

This is the first post on the FINN blog. There’ll be more — technical deep dives, field test results, updates on new features, and the occasional broader piece about where farm tech is heading.

If you want to try Finn Guidance, head to the guidance page and grab the download. If you want to follow along, check back here or find us on YouTube.

And if you’re a farmer who’s ever thought “I could build that” — you’re probably right. Give it a go.