Betaflight 4.7 New Features: GPS Return-to-Home and Advanced Filtering

Betaflight 4.7 New Features: GPS Return-to-Home and Advanced Filtering

Betaflight 4.7 represents the most significant firmware update for FPV flight controllers since the 4.0 RPM filter revolution. Two headline features — GPS Return-to-Home with autonomous landing and a completely reworked dynamic notch filter system — elevate Betaflight from a pure racing/freestyle firmware into a legitimate platform for mid-range exploration and semi-autonomous operation. This article covers both features in technical detail, plus several underappreciated improvements that deserve attention.

GPS Return-to-Home: How It Works

Betaflight’s GPS Rescue mode has existed since 4.1, but it was best described as “controlled fly-back” — the quad would turn toward home, climb to a set altitude, and fly back using GPS heading and barometer altitude. It worked reasonably well in calm conditions but struggled with wind, lacked terrain awareness, and required manual landing. Betaflight 4.7 upgrades this to a genuine Return-to-Home (RTH) system with autonomous landing, significantly improved GPS hold accuracy, and variable-speed return flight.

The RTH sequence in 4.7 follows these phases:

1. Activation trigger: RTH engages on failsafe (configurable delay, default 1 second), AUX switch, or when RSSI/LQ drops below a configurable threshold for a configurable duration. The new “smart trigger” option prevents RTH from activating during brief signal dropouts caused by proximity flying behind obstacles.
2. Climb phase: The quad stops horizontal movement and climbs at the configured climb rate (default 5 m/s) to the RTH altitude. The new “relative altitude” option adds a fixed height above the altitude where RTH was triggered, which is safer than an absolute altitude that might put you into terrain if triggered below a hill.
3. Return phase: The quad rotates toward home and flies at the configured cruise speed (default 15 m/s). 4.7 introduces “adaptive cruise” — the quad adjusts speed based on remaining battery capacity and distance. If you’re far out with low battery, it increases speed to ensure you make it back. The heading controller now uses GPS course-over-ground rather than just the target bearing, which dramatically improves tracking accuracy in crosswinds — the quad actually crabs into the wind instead of being blown off course.
4. Descend phase: At a configurable distance from home (default 50m), the quad begins descending while continuing toward home. The descent rate is automatically managed to arrive at the home point at roughly 10m altitude.
5. Landing phase: At 10m altitude above the home point, the quad transitions to a GPS-assisted hover and begins a controlled descent at the landing speed (default 1 m/s). The new landing detector uses accelerometer data to detect ground contact and disarms automatically. A “landing abort” feature on the AUX switch allows you to cancel landing and climb back to RTH altitude if the landing zone looks unsuitable.

GPS Hardware Requirements

The quality of your GPS module directly determines RTH reliability. Betaflight 4.7 supports standard UBlox M8, M9, and M10 modules, plus the newer u-blox SAM-M10Q and SAM-M8Q patch antenna modules. Key specifications:

For reliable RTH, a multi-constellation M10 module with a compass is strongly recommended. The compass (magnetometer) enables the flight controller to know the quad’s absolute heading even during low-speed hovering and landing, which is critical for the landing phase accuracy. Modules using the M10 generation acquire satellites significantly faster (typically 5-15 seconds cold start vs. 30+ seconds for M8) and maintain lock better under tree canopy.

GPS module placement is equally important. Mount the GPS on a mast or rear arm away from the VTX antenna, which is the primary source of GPS interference. Carbon fiber frames block GPS signals — do not mount the module directly on a carbon plate. The TBS GPS bracket or a 3D-printed TPU mount with at least 15mm of elevation above the frame is recommended. Always enable the SA.2 auxiliary UART at 115200 baud for GPS communication.

Configuring RTH in Betaflight 4.7

The GPS Rescue tab has been completely redesigned in 4.7 Configurator. Key parameters to set:

• RTH Altitude Mode: Choose between “Fixed” (absolute altitude above home) or “Relative” (adds a fixed offset above the altitude where RTH was triggered). For mountainous terrain, always use Relative with at least 50m offset. For flat terrain, Fixed at 80-100m works well.
• Climb Rate: 3-8 m/s. Higher values consume more battery but clear obstacles faster. 5 m/s is a good default for 5-inch quads.
• Cruise Speed: 10-20 m/s. At 15 m/s (54 km/h), a 5-inch quad covers 1km in roughly 67 seconds. Consider your battery capacity — faster cruise draws more current.
• Descent Distance: The distance from home where descent begins. Default 50m works for most setups. Increase to 100m if you’re returning from very high altitude.
• Landing Speed: 0.5-2 m/s. 1 m/s is gentle and controllable. 2 m/s is noticeably firm on touchdown. Slower is safer for the quad but takes longer.
• Min Satellites: Set to 8 minimum. GPS Rescue will not engage below this count. Do not lower this — GPS accuracy degrades significantly below 8 satellites.
• Allow Arming without GPS Fix: Disable this for RTH builds. You want a solid home point locked before takeoff.

The new “GPS Rescue Simulator” in Betaflight Configurator 10.10 allows you to test RTH behavior on the bench. It simulates the quad’s position, altitude, and heading and shows exactly what the flight controller would command at each phase. This is invaluable for verifying your configuration before risking a real failsafe.

Advanced Dynamic Filtering: The Notch Filter Overhaul

Betaflight 4.7 introduces an entirely rewritten dynamic notch filter engine that represents the most significant filtering improvement since RPM filtering arrived in 4.0. The previous system used three independent dynamic notch filters that each tracked a single peak. The new system uses a unified “Dynamic Harmonic Notch” (DHN) that tracks the fundamental motor frequency and automatically places notches at the fundamental plus the 2nd through 6th harmonics.

Why this matters: Motor noise is not a single frequency but a harmonic series. A motor spinning at 30,000 RPM (500 Hz electrical) produces mechanical noise peaks at 500 Hz, 1,000 Hz, 1,500 Hz, 2,000 Hz, etc. The old system could track at most three of these peaks, and they competed with each other for filter slots. The new DHN tracks the fundamental (derived from RPM telemetry or gyro FFT) and places notches at all harmonics simultaneously — up to 6 notches from a single tracked frequency.

Results in real-world testing:

• 40-60% reduction in gyro noise floor across the 100-500 Hz band where motor noise dominates, compared to Betaflight 4.5’s filtering on the same quad.
• Reduced filter delay. Because the DHN is more efficient at noise rejection, the low-pass filter cutoffs can be raised by 20-40 Hz, reducing total filter delay by approximately 1.5-2ms. This translates directly to better propwash handling and sharper stick feel.
• Fewer “hot motors” from excess D-term noise. Cleaner gyro signals mean D-term isn’t amplifying residual noise, reducing motor temperature rise by 5-10°C on previously marginal setups.

Configuring the New Dynamic Harmonic Notch

The Filters tab in 4.7 has a simplified layout. The critical new parameters:

• Dynamic Harmonic Notch Range: Set the low end to your minimum motor RPM frequency (e.g., 100 Hz for 6,000 RPM) and the high end to your maximum (e.g., 550 Hz for 33,000 RPM). The DHN only operates within this band.
• Number of Harmonics: Default 4, maximum 6. More harmonics = cleaner signal but marginally more filter delay. For noisy 5-inch builds, 5-6 harmonics is recommended. For smooth 3-inch builds, 3-4 is sufficient.
• Q Factor: Controls notch width. Default 1.5 works well. Increase to 2.0 for very noisy builds (broadens the notch to catch more noise at the cost of removing more signal). Decrease to 1.0 for ultra-clean builds (narrower notch, less signal removed).
• Gyro Lowpass 1 Cutoff: With DHN active, most builds can run 250-300 Hz (up from 200-250 Hz in 4.5). Test incrementally — raise cutoff 20 Hz at a time and watch motor temps.
• D-term Lowpass 1 Cutoff: Similarly, 170-200 Hz is achievable on many builds (up from 140-170 Hz in 4.5).

The recommended tuning process: start with the 4.7 default filter settings, fly a pack with moderate flying, check motor temps and Blackbox logs. If motors are cool (<50°C) and the gyro spectrogram shows clean traces, raise the low-pass cutoffs incrementally. If you see noise spikes at harmonics in the spectrogram, increase the number of harmonics tracked or widen the Q factor before lowering filter cutoffs.

Additional 4.7 Improvements Worth Knowing

• Bidirectional DShot improvements: RPM filter now recovers from desync events more gracefully. Previously, a single missed RPM telemetry frame could cause a brief filter glitch. 4.7 uses a predictive Kalman-style estimator to bridge missing frames for up to 50ms.
• OSD Profile switching: You can now switch between three OSD profiles via AUX switch, enabling different layouts for racing (minimal OSD), freestyle (battery and timer only), and long range (full telemetry with GPS coordinates and efficiency data).
• TPA (Throttle PID Attenuation) curve editor: Instead of a single breakpoint and percentage, TPA is now a 7-point spline curve. This allows precise PID reduction at specific throttle ranges — for example, aggressive reduction at 30-50% throttle for smooth mid-throttle cinematic flying while maintaining full PIDs at zero throttle for sharp flips and at full throttle for racing precision.
• Improved CRSF telemetry speed: Crossfire telemetry now negotiates higher baud rates (up to 1 Mbps) with TBS Crossfire and Tracer receivers running current firmware, enabling full-rate GPS and attitude telemetry that was previously throttled.
• Preset system 2.0: The community preset library is now integrated directly into the Configurator with version tracking, one-click apply, and diff-based preview so you can see exactly what CLI commands a preset will execute before applying.

Should You Upgrade?

For any quad carrying a GPS module — and especially for mid-range and long-range builds — Betaflight 4.7 is a no-brainer upgrade. The RTH improvements alone justify the flash, and the real-world stories of quads autonomously returning from 3km+ out with the new system are stacking up on forums and YouTube. The DHN filtering improvements benefit every build regardless of use case — lower noise floor and reduced filter delay make the quad fly better, period.

The upgrade path is straightforward: flash the 4.7 target for your FC via Betaflight Configurator 10.10, apply “Keep settings” when prompted if coming from 4.5 or 4.6, then immediately go to the Presets tab and apply the “4.7 Default Tune” preset for your build type. This preset configures the optimal DHN and filter cutoffs for your specific quad class (5″ freestyle, 7″ LR, 3″ toothpick, etc.). Then perform a calibration flight to let the dynamic notch settle on your actual motor frequencies, and you’re done.

One caveat: the F7 processor remains the recommended minimum for 4.7. F4 flight controllers running RPM filtering, GPS, and the full DHN at 8kHz may see CPU load exceed 50%, which is the threshold where cycle time stability begins to degrade. If you’re on F4, consider disabling features you don’t use (e.g., LED strip, accelerometer if you fly acro-only) to reduce CPU load, or disable the highest harmonics of DHN.