Abstract

As drones move towards large-scale and autonomous operation, flight control systems require not only precise algorithms but also a reliable “sensory nervous system” that can be trusted in complex environments. The PX4 open-source flight control system, serving as the “intelligent brain” of the global drone ecosystem, often finds its performance ceiling limited by its most fundamental sensors—especially the GNSS receiver that provides an absolute position reference. The deep integration of the Septentrio mosaic-X5, an industry-leading multi-frequency, multi-constellation, high-precision GNSS module renowned for its anti-jamming and anti-spoofing capabilities, with PX4 is establishing a “trusted defense line” for autonomous drone systems, spanning from positioning and navigation to mission execution.

Empowering UAV Flight Control Systems with High-Precision GNSS Technology

In the era of autonomous flight, accurate and reliable spatiotemporal information is the core guarantee for drones to achieve intelligent flight control and autonomous decision-making. The Septentrio mosaic-X5 GNSS receiver provides a high-performance, high-reliability positioning and heading solution for drone flight control systems based on PX4, featuring industry-leading centimeter-level RTK positioning capability and multi-antenna real-time heading output. Supporting full-constellation, multi-frequency signal tracking and combined with AIM+ anti-jamming and anti-spoofing technology, it ensures stable and precise position information output even in complex electromagnetic environments such as urban and industrial areas, significantly enhancing the PX4 system’s environmental adaptability and mission reliability during dynamic flight. Through standard serial ports and rich interface protocols, the mosaic-X5 can be seamlessly integrated into the PX4 software and hardware ecosystem, supporting rapid deployment and flexible configuration. It empowers drones to achieve high-precision autonomous flight and stable control in scenarios such as precision agriculture, surveying and modeling, and infrastructure inspection, acting as a key navigation engine propelling industrial-grade drone applications towards higher levels of intelligence.

Introduction to PX4 Open-Source Flight Control

PX4 is an open-source flight control system, also known as the “King of Open-Source Flight Controllers.” It evolved from PIXHAWK, a software and hardware project at the Computer Vision and Geometry Lab of ETH Zurich. PX4 aims to provide a low-cost, high-performance, high-end autopilot for academic, hobbyist, and industrial communities. It is supported by a global community and developed collaboratively by world-class developers from industry and academia. Currently, it is supported and operated by the Dronecode Foundation.

PX4 follows the BSD license, which allows the open-source software to be used for commercial purposes after secondary development. It is widely used for visual navigation, visual obstacle avoidance, multi-agent collaboration, target tracking, and more, and is often referred to as the “Android” of the drone world.

PX4 Open-Source Flight Control Features

Flight Control: PX4 can control drone flight, including attitude control, position control, altitude control, and speed control. By receiving data from sensors and remote controllers, PX4 calculates the drone’s flight status and issues corresponding control commands to guide the drone along a predetermined trajectory.

Sensor Fusion: PX4 integrates various sensors, such as gyroscopes, accelerometers, magnetometers, barometers, and GPS. By fusing data from these sensors, it obtains accurate attitude and position information for the drone.

Autonomous Navigation: PX4 supports multiple autonomous navigation modes, such as GPS navigation, visual navigation, and laser navigation. Using these modes, drones can fly autonomously without remote control signals, enabling functions like position hold, autonomous return-to-home, and automated mission flight.

Mission Planning: PX4 supports mission planning functions, allowing it to automatically generate flight trajectories based on predefined mission objectives and control the drone to follow them. This enables drones to perform complex tasks such as search and rescue, environmental monitoring, and agricultural crop protection.

Data Processing and Analysis: PX4 has powerful data processing and analysis capabilities, enabling real-time handling of data from sensors and cameras. This data facilitates real-time monitoring and diagnostics of the drone, as well as environmental perception and recognition.

Core Advantages of Septentrio mosaic-X5

AIM+ (Advanced Interference Mitigation software+)

Types of Interference Protected Against:

Spurious peaks from radio amateurs and digital TV

Signals from non-malicious transmitters (e.g., amateur radios, TV transmitters) that may produce unintended strong signal peaks (spurious emissions) outside their operating bands due to design flaws or malfunctions. These strong peaks can drown out weak satellite navigation signals, causing receiver lock loss.

Signals from Inmarsat and Iridium satellite systems

Inmarsat and Iridium satellite systems use frequency bands adjacent to or partially overlapping GNSS bands. Their powerful downlink signals can cause out-of-band blocking or adjacent-channel interference to nearby GNSS receivers.

DME (Distance Measuring Equipment) pulse interference near airports

DME is an aviation navigation device operating in the 960-1215 MHz band, overlapping the GPS L5 band. The high-power pulse pairs it emits can severely interfere with satellite signals, potentially causing frequent satellite loss and unreliable positioning near airports.

Broadband interference from “chirp” jammers

“Chirp” jammers are common malicious jamming devices that rapidly and periodically scan a wide frequency band (e.g., the entire GNSS band), generating transient but full-bandwidth powerful interference. Traditional static filters struggle to cope, effectively disabling most commercial receivers.

Solutions Included in AIM+

The software addresses the aforementioned interference through the following advanced features:

Adaptive Notch Filtering and Band Reconfiguration

Adaptive Notch Filter: The software monitors the spectrum in real-time, automatically identifies the center frequency and bandwidth of narrowband interference (e.g., spurious peaks, fixed-frequency interference), and dynamically creates a deep “notch” to filter it out while maximizing the preservation of useful GNSS signals.

Band Reconfiguration: In the face of strong interference in specific frequency bands, the system can intelligently adjust its reception strategy. For example, it may temporarily rely more on unaffected bands (e.g., L5) or reconfigure signal combinations from different bands to bypass interference.

Unique Resilience Against “Chirp” Jammers

This is a standout advantage of AIM+. The software algorithms are specifically optimized for the fast time-varying characteristics of chirp signals.

It likely employs time-frequency analysis techniques (e.g., Short-Time Fourier Transform) to track and predict the trajectory of chirp interference, performing joint filtering or cancellation in the time-frequency domain to effectively suppress this most challenging broadband swept-frequency interference.

Onboard Spectrum Viewer for Interference Detection/Location

Provides a visualization tool allowing operators to view the RF environment spectrum in real-time.

Purpose:

Detection: Visually identify the presence, type, and strength of interfering signals.

Location: Combined with antenna arrays or mobile platforms, it can assist in determining the approximate direction or location of interference sources.

Diagnosis: Evaluate the effectiveness of anti-jamming measures (like AIM+).

Full-Band High-Precision Real-Time Positioning

Supports all existing and future global navigation satellite systems, with 448 hardware channels for comprehensive signal coverage.

Provides centimeter-level RTK positioning capability: horizontal accuracy of 0.6 cm + 0.5 ppm, vertical accuracy of 1 cm + 1 ppm, with initialization as fast as 7 seconds.

Offers up to 100 Hz update rate and low latency below 10 ms, meeting the real-time requirements of high-dynamic drone flight control.

Provides multiple standard interfaces and protocols for seamless integration into open-source flight control systems like PX4 and ArduPilot.

Advanced Interference Protection & High Reliability

Equipped with industry-leading AIM+ anti-jamming and anti-spoofing technology to effectively counter various electromagnetic interference.

Integrates patented technologies: APME+ multipath mitigation, IONO+ ionospheric protection, LOCK+ vibration-robust tracking.

Operating temperature range: -40°C to +85°C, compliant with MIL-STD-810G vibration standards, suitable for harsh environments.

Typical power consumption of only 0.6 W, combining high performance with low power efficiency, supported by free lifetime firmware upgrades.

mosaic-X5 + PX4: Building a Professional-Grade Autonomous System

True Autonomy Requires Anti-Jamming

PX4 achieves precise control of drone attitude, position, speed, and trajectory through real-time fusion of multi-sensor data. However, near power lines, industrial sites, dense urban areas, or in risk environments with potential malicious interference, traditional GPS signals are highly susceptible to jamming or spoofing, leading to position drift, loss, or even induced drone control loss. The AIM+ technology built into mosaic-X5 acts like a “spectrum sentinel” for PX4. It continuously monitors GNSS bands, identifying and suppressing various interferences in real-time—from simple continuous wave to complex swept-frequency types—while effectively detecting and resisting spoofing attacks through multi-dimensional signal characteristic analysis. This ensures the position information PX4 receives remains authentic and reliable, guaranteeing stable flight and safe return even during missions in complex electromagnetic environments, granting the autonomous flight system genuine environmental resilience.

High Precision & High Integrity

PX4’s sensor fusion algorithms heavily rely on GNSS data to correct inertial navigation system error accumulation and provide a global position reference. Leveraging its multi-frequency (L1/L2/L5) and full-constellation tracking capabilities, mosaic-X5 delivers unprecedented signal redundancy and observation quality. Its high update rate (up to 100 Hz) and extremely low latency (below 10 ms) perfectly match the requirements of PX4’s high-speed control loops. Whether performing high-dynamic maneuvers or conducting precise inspection tasks in high-vibration environments, mosaic-X5 consistently outputs stable, continuous, and high-integrity position, velocity, and time information, significantly enhancing the overall accuracy and reliability of PX4’s state estimation and laying a solid foundation for complex navigation decisions.

From Precise Hovering to Repeatable Tracks

For professional applications like surveying, inspection, and precision agriculture, the value of drones lies in their repeatable, high-precision automated operation capabilities. mosaic-X5 provides real-time centimeter-level RTK positioning and post-processing PPK support, enabling PX4-powered drones to achieve takeoff, landing, point hovering, and track following with centimeter-level precision. Whether continuously aligning with insulators during power line inspection or ensuring strip overlap for high-resolution mapping, mosaic-X5 guarantees consistent trajectory for every flight. Simultaneously, its anti-jamming and anti-spoofing characteristics safeguard data authenticity and operational security during automated missions in sensitive or high-risk areas, preventing task interruption or misleading results due to signal issues.

Plug-and-Play, High-Reliability Positioning Solution

mosaic-X5 is designed with embedded integration needs in mind. It outputs the NMEA protocol natively supported by PX4 via a standard UART serial interface, allowing developers to quickly integrate it as a plug-and-play high-performance GPS module into existing PX4 systems without modifying core flight control code. For users requiring advanced functionalities—such as integrating RTK differential correction signals, logging raw observation data for post-processing, or obtaining detailed interference spectrum reports—Septentrio provides comprehensive configuration tools (RxTools) and ROS drivers. This enables flexible collaboration with the PX4 ecosystem, facilitating deep integration of the positioning subsystem with flight control, mission planning, and payload management modules, greatly shortening product development cycles.

From Positioning Data to System-Level Intelligence

Modern drone systems are evolving from merely executing flight commands to becoming “aerial robots” with environmental perception and intelligent decision-making capabilities. PX4’s powerful real-time data processing framework can integrate multimodal perception data from vision, LiDAR, etc. mosaic-X5 plays a crucial role here: it not only provides precise spatiotemporal tags for all perception data, but the signal quality indicators and interference flags it outputs can directly empower PX4’s decision-making layer. The flight control system can judge the credibility of positioning information based on this and proactively switch to degraded navigation modes or trigger predefined safety strategies when GNSS signals are threatened, achieving a system-wide intelligent leap from “blind reliance” to “informed decision-making.”

Summary

Choosing Septentrio mosaic-X5 is not merely selecting a high-performance GNSS receiver; it is infusing your PX4 drone system with a “strong heart” that beats steadfastly even in complex electromagnetic environments. It deeply integrates anti-jamming resilience, centimeter-level precision, and system-level intelligence, empowering drones to achieve safe, reliable, and precise full autonomy in critical missions. Let every flight be built upon a foundation of trust.

How does the mosaic-X5 improve the reliability and precision of drones in autonomous flight after integration with PX4?

After integration, the mosaic-X5 enhances the performance of PX4-based drones in the following aspects:

Anti-interference for safety: AIM+ technology ensures stable and reliable GNSS signals in complex electromagnetic environments, preventing loss of positioning or control failure due to spoofing, providing a “trusted data source” for the PX4 control loop.

High-precision positioning support: Centimeter-level RTK positioning (horizontal accuracy 0.6cm+0.5ppm), 100Hz high update rate, and low latency below 10ms meet the high dynamic control requirements of PX4, improving attitude estimation and trajectory tracking accuracy.

Optimized multi-sensor fusion: The multi-frequency, full-constellation observation data output by the mosaic-X5 provides high-integrity anchor points for inertial navigation error correction in PX4, reducing cumulative errors.

Mission-level reliability: Combined with RTK/PPK capabilities, it supports drones in achieving centimeter-level repeatable flight paths and precise hovering, suitable for missions with high consistency requirements such as mapping and inspection.

How does the hardware and interface design of the mosaic-X5 meet the integration requirements of the PX4 system?

The mosaic-X5 is designed with embedded integration in mind:

Interface compatibility: It provides standard UART serial ports, supports the NMEA protocol natively parsed by PX4, and is plug-and-play ready. It also supports other interfaces (such as SPI, USB) to meet flexible configuration needs.

Low power consumption and reliability: With typical power consumption of only 0.6W, an operating temperature range of -40°C to 85°C, and compliance with the MIL-STD-810G vibration standard, it is suitable for harsh environments.

Extended functionality support: The Septentrio configuration tool (RxTools) can be used to access RTK differential signals, record raw observation data, and integrate with ROS drivers for deep linkage with the PX4 ecosystem (e.g., mission planning, payload management).

High channel capacity: 448 hardware channels support full-constellation, multi-frequency signal tracking, providing PX4 with redundant and high-quality observation data.

How does the mosaic-X5 enable PX4-based drones to evolve from “simple execution” to “intelligent decision-making”?

The mosaic-X5 facilitates the intelligent evolution of the PX4 system through the following mechanisms:

Spatiotemporal reference labeling: Provides precise time synchronization and spatial coordinates for multimodal perception data (e.g., vision, LiDAR), supporting environmental modeling and fused perception.

Signal health output: Real-time output of signal quality indicators, interference flags, and other information enables the PX4 decision-making layer to assess positioning reliability and trigger degraded navigation modes or safety strategies (e.g., automatic return, switching to visual navigation) when GNSS is threatened.

Anti-spoofing and integrity monitoring: Identifies spoofing attacks through multi-dimensional signal feature analysis, enhancing system resilience in security-sensitive scenarios.

System-level collaboration: Combined with the open-source framework of PX4, the data from the mosaic-X5 can be directly used for advanced decision-making, such as mission replanning and dynamic obstacle avoidance, achieving the leap from “relying on positioning” to “autonomous intelligence based on trusted positioning.”