High-Precision GNSS/INS Positioning: Why Septentrio Receivers Are Key for Marine Meteorological Monitoring

As marine observation and meteorological forecasting move toward refinement and real-timeness, Unmanned Surface Vessels (USVs) have become cutting-edge platforms for deploying mobile weather stations, collecting boundary layer data, and monitoring extreme weather. On the vast ocean, systems face challenges such as continuous shaking, salt spray corrosion, signal multipath, and occasional obstruction. Their navigation and attitude reference systems must provide stable, continuous, and precise position and 3D attitude information. The Septentrio AsteRx-i3 S Pro+, a high-performance GNSS/INS receiver with an innovative split IMU design, delivers centimeter-level positioning and high-fidelity motion sensing capabilities for meteorological USVs, serving as the core technical cornerstone to ensure scientific data is tagged with accurate spatiotemporal information.

Why Meteorological USVs Require High-Performance GNSS/INS Receivers

Marine meteorological monitoring missions are unique, imposing extremely high requirements on the reliability, accuracy, and environmental adaptability of navigation systems:

• Dynamic Attitude & True Motion Sensing: Vessels pitch, roll, and heave with waves, requiring precise measurement of true motion to calibrate data from onboard meteorological sensors (e.g., anemometers, temperature-humidity probes).
• Complex Signal Environment: Significant multipath reflection effects on the sea surface, combined with occasional obstruction by ship bridges or equipment, demand systems with strong anti-multipath capabilities and short-term signal interruption retention.
• Harsh Marine Environment: Long-term exposure to high humidity, high salt spray, and wide temperature variations requires equipment to have excellent environmental protection and long-term reliability.
• Spatiotemporal Consistency of Data: Strict binding of meteorological data to high-precision position, attitude, and timestamps is a prerequisite for subsequent data assimilation and model validation.

With the flexible installation advantage of its split IMU, multi-frequency multi-constellation tracking, advanced GNSS+ anti-interference suite, and industrial-grade reliability, the Septentrio AsteRx-i3 S Pro+ has become an ideal solution for meteorological USVs to achieve precise navigation, stable operations, and high-quality data collection.

Core Advantages: An “Intelligent Perception Hub” Built for Meteorological USVs

Through its unique hardware architecture and GNSS+ software suite, the AsteRx-i3 S Pro+ provides USVs with “motion sensing” capabilities beyond traditional positioning.

Key Performance Parameters

1. Full-Constellation Multi-Frequency Reception: 544 hardware channels, simultaneously tracking GPS, BeiDou, Galileo, GLONASS, QZSS, SBAS, and other signals to ensure reliable coverage across global marine areas.
2. Centimeter-Level RTK-INS Positioning Accuracy: Horizontal accuracy of 0.6 cm + 0.5 ppm, vertical accuracy of 1.0 cm + 1 ppm (baseline < 40 km), providing precise geographic reference for marine observation.
3. Split IMU Design: The IMU module (26.8×18.8×9.5 mm, weight 10g) can be independently installed at key motion points of the hull (e.g., mast base) to directly measure true attitude, while the main board can be placed inside the cabin.
4. High-Precision Attitude Output: Supports dual-antenna configuration, with heading accuracy up to 0.15° (RTK mode) and pitch/roll accuracy of 0.02°, accurately reflecting the 3D attitude of the vessel.
5. Anti-Jamming & Anti-Spoofing: Integrates AIM+ technology to real-time suppress various radio frequency interference and spoofing signals, ensuring data security in busy waterways or complex electromagnetic environments.
6. High Update Rate & Low Latency: Combined position output rate up to 100 Hz, latency < 20 ms, meeting real-time wave compensation and track control requirements.
7. Rugged & Durable Design: Both the main board and IMU comply with MIL-STD-810G vibration standards; the main board operates within a temperature range of -20°C to +85°C, adapting to the wide temperature environment at sea.

GNSS+ Technology Suite: Ensuring Continuous & Reliable Operations in Complex Sea Conditions

• AIM+: Advanced interference monitoring and suppression, addressing co-frequency interference from marine communication equipment, radar, etc., to ensure a clean data link.
• APME+: Posteriori multipath estimation, effectively suppressing multipath errors caused by specular reflection on the sea surface and improving positioning accuracy of low-elevation satellite signals.
• LOCK+: Enhanced tracking robustness, ensuring stable satellite lock during continuous vessel vibration and dynamic stress to avoid signal loss.
• IONO+: Ionospheric scintillation suppression, particularly suitable for low-latitude or geomagnetically active marine areas, improving positioning stability.

Split IMU: Achieving Optimal Motion Measurement & Flexible Integration

• Installation Flexibility: The miniature IMU can be directly installed near sensors or at the hull’s center of gravity to accurately perceive true motion, avoiding motion attenuation and phase delay caused by installation positions far from measurement points or structural transmission.
• Simplified Integration: The main board can be placed in a standard position inside the electronic cabin and connected to the IMU via cables, simplifying system wiring and improving maintenance convenience.
• Data Synchronization: GNSS and IMU data are perfectly synchronized at the hardware level, providing data streams with a unified spatiotemporal reference for easy fusion with meteorological sensor data.

Easy Integration & Adaptation to Shipborne Systems

• Rich Interfaces: Offers 4 high-speed serial ports, USB, and Ethernet, supporting SBF, NMEA, RTCM, and other standard protocols for easy integration with shipborne autopilots and data loggers.
• Powerful Software Support: Built-in WebUI for convenient configuration, providing automatic lever arm optimization tools and cross-platform SDK to accelerate system debugging and development.
• Low-Power Operation: Power consumption of approximately 1.4W for full-constellation multi-frequency tracking, helping extend the USV’s endurance.

Typical Application Scenarios in Meteorological USV Systems

Precise Marine Meteorological Profile Observation

Combined with centimeter-level positioning and high-precision attitude data, USVs can sail accurately along preset profiles while calibrating onboard meteorological sensor data, obtaining spatiotemporally matched vertical profiles of temperature, salinity, current, and meteorological elements.

Typhoon/Storm Front Monitoring

In severe sea conditions, its rugged design and anti-interference capabilities ensure the navigation system operates continuously, supporting USVs to safely and autonomously approach and observe storm structures, collecting valuable first-hand data.

Long-Term Fixed-Point Observation of Air-Sea Flux

Through high-precision fixed-point hovering and attitude maintenance capabilities, it supports USVs to conduct long-term continuous observation in specific marine areas, providing high-precision flux data for researching air-sea interactions.

Multi-Platform Collaborative Networked Observation

Multiple USVs equipped with the same type of receiver can form an observation network, sharing a high-precision spatiotemporal reference to achieve synchronous, multi-dimensional, and three-dimensional observation of marine meteorological phenomena.

Summary

-The Septentrio AsteRx-i3 S Pro+ is a high-performance GNSS/INS receiver with an innovative split IMU design, optimized specifically for high-precision navigation and motion sensing needs in harsh marine environments.

-It achieves a perfect combination of anti-interference, anti-multipath, precise motion measurement, and high reliability through the GNSS+ technology suite (AIM+, APME+, LOCK+, IONO+) and split IMU hardware design.

-Its application value lies in providing meteorological USVs with centimeter-level positioning, sub-degree attitude sensing, and nanosecond-level time synchronization capabilities, greatly enhancing the spatial accuracy, temporal consistency, and scientific value of marine meteorological observation data.

-With rich interfaces, flexible configuration, and ruggedness, it can be quickly integrated into various Unmanned Surface Vessel platforms, serving as a key enabling component for building the next generation of intelligent and precise marine mobile observation stations.

Targeted Q&A Section

Q: What advantages does the split IMU design offer when the hull shakes violently due to surges?

A: The split IMU allows the miniature sensor to be directly installed at positions with the most significant hull motion or near sensors, thereby more directly and accurately measuring true angular motion and linear acceleration. This avoids motion attenuation and phase delay caused by installation positions far from measurement points or structural transmission, significantly improving attitude measurement accuracy and data authenticity.

Q: How does the device achieve time synchronization with meteorological data collection systems?

A: The AsteRx-i3 S Pro+ provides high-precision xPPS pulse output (accuracy 5 ns) and event marking function (accuracy < 20 ns). The meteorological collection system can receive this pulse signal as a unified time base, accurately aligning various sensor data with the millisecond-level timestamps and geographic coordinates provided by GNSS/INS.

Q: Is a dual-antenna configuration necessary for heading measurement at sea?

A: Absolutely necessary. The heading information provided by dual antennas is independent of magnetic compasses, completely unaffected by magnetic interference from shipborne steel equipment. It can provide stable and reliable true north heading at any geographic latitude (including near the magnetic poles), which is crucial for ocean navigation and observation tasks requiring precise pointing.

Q: What is the long-term reliability of the device in the high salt spray environment at sea?

A: The product is designed in accordance with strict industrial and reliability standards. Its circuit boards use protective coatings meeting maritime environmental requirements, and connectors are high-reliability models. The entire device has passed wide-temperature, vibration, and humidity tests, enabling it to withstand the harsh environment of long-term marine operations and ensure stable long-term operation.