Diagnostic positioning metrology: decoding carrier-phase ambiguity, satellite signal-to-noise ratios (SNR), and restoring high-precision fixes.
Understanding the Two Operational States of RTK GNSS
In the status panel of your robotic mower app, you will observe two primary satellite statuses: “RTK Fix” (colored green) and “RTK Float” (colored yellow or orange). Understanding the mathematical difference between these states is essential for diagnosing unexpected mower stops and boundary navigation errors.
RTK Fix: Centimeter-Level Integer Resolution
When the status reads “RTK Fix”, the mathematical Kalman filter has successfully resolved the exact integer number of radio wavelengths between multiple orbiting satellites and both antennas (carrier-phase integer ambiguity resolution). In “Fix” mode, the mower knows its physical real-world coordinates with absolute precision down to 1.0 to 2.0 centimeters, safely cutting within inches of obstacles.
RTK Float: Ambiguity and Loss of Precision
When the status drops to “RTK Float”, satellite signals are noisy, partially obstructed, or suffering multipath reflections. The algorithm cannot definitively resolve the exact wave cycle, falling back to a statistical floating estimate. Positioning accuracy degrades from 2cm to 30-50cm. Because a 50cm error could cause the mower to drive into a swimming pool or flower bed, safety algorithms immediately stop mower motion until “Fix” is re-established.
Technical Specifications & Engineering Matrix
| RTK State | Algorithm Calculation | Position Accuracy | Mower Action | Common Cause |
|---|---|---|---|---|
| RTK Fix (Green) | Integer Ambiguity Resolved | 1.0 – 2.0 cm (Pinpoint) | Full Autonomous Mowing Active | Clean 360° Sky Horizon on Both Antennas |
| RTK Float (Yellow) | Statistical Approximation Only | 20 – 50 cm (Uncertain) | Mower Halts / Vision AI Takes Over | Partial Tree Obstruction / Building Shadow |
| Single Point GPS (Red) | Standard Consumer GPS | 3 – 5 Meters (Hazardous) | Emergency Safety Halt & Shutdown | RTK Base Station Power / Radio Link Lost |
| Zero Signal (Grey) | No Satellite Reception | None (Blind) | Total Shutdown | Inside Closed Garage / Metal Shed |
💡 Expert Field Recommendation
Open the diagnostic satellite telemetry screen in your mower app: check “Shared Satellites”. To achieve a solid RTK Fix, the mower and base station must share at least 15 to 20 identical high-SNR satellites simultaneously (L1 and L2 frequencies across GPS, Galileo, and GLONASS).
Diagnostic Troubleshooting Checklist
- Mower Permanently Stuck in “RTK Float” in Middle of Open Lawn: The sub-GHz radio communication link between base station and mower is failing; re-pair radio channels in the app or install an external high-gain radio antenna on the base station.
- Status Flaps from Fix to Float Every Few Minutes: A nearby power transformer, amateur radio antenna, or high-voltage transmission line is generating localized RF noise on GNSS frequencies.
- Base Station Reports Zero Satellites: Check antenna coaxial cable connections; ensure the SMA or IPEX antenna connector is threaded firmly and not cross-threaded.
Frequently Asked Questions
What is the minimum number of satellites needed for RTK Fix?
While basic GPS requires 4 satellites, high-precision RTK multi-band systems typically require at least 12 to 16 shared dual-frequency satellites for integer fix resolution.
Does cloudy or rainy weather cause RTK Float?
Heavy clouds have minimal impact on microwave GPS signals, but dense moisture trapped on tree leaves can attenuate signals beneath canopies.
Article researched, lab-tested, and verified by Brett Sorenson, dedicated technical specialist and editorial contributor.
