What is Finn Guidance?
Finn Guidance is a free, open-source GPS lightbar application written in Rust. It turns any Windows laptop and a USB GPS module into a working guidance system for your tractor, sprayer, or spreader.
No proprietary hardware. No annual subscriptions. No dealer install. Just plug in, set your A-B line, and drive.
Download
Current version: v0.1.0 (early release)
System requirements: Windows 10 or later, any laptop with a USB port.
Quick Start
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Get the GPS module — You’ll need a Quectel LC29H DA module on a USB breakout board. Available in our shop or from electronics suppliers.
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Plug it in — Connect the GPS module to any USB port. Finn Guidance will auto-detect the COM port.
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Launch the software — Run
finn-guidance.exe. No installation required. -
Set your A-B line — Drive to point A at one end of your paddock and press ‘Set A’. Drive to point B at the other end and press ‘Set B’. Your reference line is locked in.
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Follow the lightbar — The on-screen lightbar shows your cross-track error. Centre segments mean you’re on line. Drift left or right and the bar tells you which way to correct.
Features
GPS & Navigation
- Plug-and-play USB GPS support (Quectel LC29H DA)
- COM port auto-detection — no driver configuration needed
- NMEA parsing with epoch deduplication for clean data
- Position interpolation for smooth display between 1Hz GPS fixes
- Heading-up map view with layered rendering
Guidance
- A-B line creation with visual lightbar display
- Configurable lightbar segment width (20cm default, tighten with RTK)
- Auto-pass selection based on implement width
- Width and overlap controls for different implements
- Nudge feature for inter-row sowing alignment
Data Management
- Save and load A-B lines grouped by field
- JSON export/import for transferring lines between machines
- Coverage logging with SQLite storage and CSV export
- Distance-filtered recording for clean coverage maps
Hardware
| Component | Details |
|---|---|
| GPS Module | Quectel LC29H DA on USB breakout board |
| Fix Rate | 1Hz (hardware limit of LC29H DA firmware) |
| Accuracy (standalone) | ~1–2m pass-to-pass (suitable for broadacre lightbar use) |
| Accuracy (with RTK) | ~2cm (RTK support planned) |
| Connection | USB — auto-detected, no drivers required |
| Mounting | Magnetic or suction mount on roof, cable through window |
Roadmap
What’s coming next for Finn Guidance:
- RTK support — Sub-centimetre accuracy with correction services
- Grid realignment — Shift your guidance grid to align with existing rows
- Boundary mapping — Record paddock boundaries for area calculations
- Multi-machine sync — Share live position data between machines
- Android companion — Lightweight display for a tablet on the dash
Open Source
Finn Guidance is open source and free to use. The code is written in Rust with an egui interface, designed to be fast, reliable, and easy to build on.
Want to contribute, report a bug, or request a feature? Head to the GitHub repository.