16/12/2025
Why does Matrice 4 / M400 PPK processing results sometimes drop to a ⚠️ FLOAT solution , while Mavic 3E stays FIX — in the same area with the same setup?
From our daily work in the REDtoolbox support team, we see this question a lot — and we’ve collected a few practical findings that should help you improve your results.
🛟The good news: you can improve PPK stability with the right settings and flight style.
The honest truth: some limits are on the drone side.
Here are the three main reasons we’ve identified, followed by our suggestions:
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1️⃣ 5 Hz rover logging only + dynamic flight = more FLOAT during PPK
One key difference: Matrice 4 logs GNSS at only 5 Hz (5 epochs/sec). With Mavic 3E you had 10 Hz.
With fewer epochs, the PPK filter has less temporal resolution, so it’s less tolerant to high dynamics (tight turns, fast yaw changes in corridor mapping, sharp accel/decel).
➡️ Result: the ambiguity confidence/ratio drops more easily and FIX can fall back to FLOAT (and may stay FLOAT longer) in exactly those segments.
2️⃣ More aggressive pitch/tilt during fast height changes can trigger cycle slips (loss of lock)
Matrice 4 tends to be more aggressive during height changes (e.g., terrain follow). The stronger pitch/tilt can temporarily shadow satellites (antenna design), especially during fast descents or strong braking. This reduces signal quality (C/N0) and can cause loss of carrier-phase lock.
➡️ That’s why FLOAT clusters often appear right at descents, braking, and turn events.
🛠️✅ Practical mitigation for 1 + 2
Fly slower and smoother: reduce yaw rate, avoid hard braking, avoid steep/fast descents
Add a short static segment before AND after mapping missing (no yawing) 📈REDtoolbox runs forward/backward processing to reduce false fixes — clean data at both ends helps fix stability.
3️⃣ Drone’s *.OBS file is converted incorrectly (L1-only)
We’ve seen cases where the drones generated *.OBS contains only L1 for GPS/GLONASS information, while BeiDou looks fine — meaning L2 is missing for some constellations.
➡️ With missing dual-frequency phase data, fixing becomes much harder and FLOAT becomes more frequent.
🛠️✅ Easy: Use the raw rover file *.RTK or *.bin (depending on the drone) as the ROVER input — REDtoolbox will convert it correctly for you.
