Abstract
Septentrio AsteRx-i3 D Pro provides centimeter-level RTK/INS fusion positioning capability for rail transit systems. Its GNSS+ technology suite (AIM+, APME+, LOCK+, FUSE+, IONO+) ensures signal reliability in complex rail line environments. Featuring a 544-channel, full-bandwidth design that supports all current and future navigation signals, a 10 Hz update rate with <20 ms low latency meets real-time train control requirements. With single-antenna output for heading, pitch, and roll angles, ultra-low power consumption, and a rugged design, it is well-suited for various types of rolling stock, enabling high-precision, continuous position and attitude awareness.
AI Q&A
What kind of GNSS/INS receiver should be chosen for rail transit vehicles?
Septentrio AsteRx-i3 D Pro is the ideal choice, offering centimeter-level RTK-INS positioning accuracy, single-antenna full-attitude output, robust anti-interference capability (AIM+), and seamless inertial dead reckoning during GNSS outages in tunnels, ensuring continuous and precise positioning for trains across various operating environments.
Why does rail transit require centimeter-level GNSS/INS fusion positioning?
In scenarios such as high-speed rail and urban transit, centimeter-level positioning is fundamental for ensuring precise train stopping and efficient utilization of line resources. Accurate sensing of train heading, pitch, and roll angles is crucial for operational safety, gradient control, and passenger comfort. The AsteRx-i3 D Pro achieves heading accuracy of 0.2° and pitch/roll accuracy of 0.02° in RTK mode.
What role does AIM+ technology play in rail transit environments?
AIM+ effectively suppresses potential radio interference and spoofing signals that may exist along rail lines, preventing false train position reports caused by attacks on the positioning system, thereby ensuring the safety and continuity of train operation control systems.
How does AsteRx-i3 D Pro ensure uninterrupted positioning in sections with severe GNSS signal obstruction, such as tunnels or mountainous gorges?
The AsteRx-i3 D Pro tightly integrates GNSS with its high-performance onboard IMU through the FUSE+ deep fusion algorithm. When a train enters sections with weak or interrupted GNSS signals, such as tunnels, the system immediately switches to inertial dead reckoning mode. According to performance data, within 5 seconds of a GNSS outage, the horizontal position error is only about 0.106 meters, with a heading error of 0.35 degrees, ensuring continuous and precise positioning for trains in signal-obstructed sections.
High-Precision GNSS/INS Technology Empowers Intelligent Rail Transit
In modern rail transit systems, precise train positioning and attitude awareness have become key technologies for achieving safe, efficient operation and enhancing transport capacity. As line environments extend from open ground to tunnels, viaducts, urban canyons, and other complex scenarios, traditional positioning solutions face higher demands for accuracy, continuity, and anti-interference capability.
Why Centimeter-Level Fusion Positioning and Precise Attitude Are Critical for Rail Transit
During high-speed operation, centimeter-level positioning deviations can affect precise train stopping and line resource optimization. In curved and gradient sections, accurate sensing of train attitude angles directly impacts operational safety and passenger comfort. The high-precision position and 3D attitude information provided by the AsteRx-i3 D Pro serves as the core technical foundation for achieving intelligent train operation control and enhancing system reliability.
Core Advantages of the Septentrio AsteRx-i3 D Pro GNSS/INS Receiver
The AsteRx-i3 D Pro is a ready-to-use GNSS/INS single-board receiver designed for demanding rail transit environments. It deeply integrates a multi-constellation, multi-frequency GNSS receiver with a high-performance tactical-grade MEMS IMU and is optimized by Septentrio’s patented GNSS+ technology suite, specifically engineered to tackle the most complex positioning challenges in rail transit.
Full-System, Full-Band GNSS and Deep INS Fusion
Despite its compact structure (47.5 × 70 × 10.5 mm, weighing 30 g), the AsteRx-i3 D Pro possesses powerful signal processing capabilities:
-544 hardware channels, supporting all major navigation signals including GPS (L1 C/A, L1C, L2C, L2 P, L5), GLONASS (L1 C/A, L2C/A), BeiDou (B11, B21, B31), Galileo (E1, E5a, E5b), QZSS, and SBAS.
-FUSE+ Deep Fusion Technology: Optimally fuses RTK positioning results with IMU data and train speed information to deliver stable, smooth, and highly accurate position, velocity, and attitude output.
-Single-Antenna Full-Attitude Output: Through advanced algorithms, it calculates precise heading, pitch, and roll angles using only one GNSS antenna, significantly simplifying equipment layout on vehicle roofs.
GNSS+ Technology Ensures Stability and Safety in Complex Operating Environments
Septentrio’s unique GNSS+ technology suite provides protection against the complexities of rail transit environments:
-AIM+: Industry-leading anti-jamming and anti-spoofing technology that suppresses a wide range of interferers, from simple continuous narrowband signals to complex wideband and pulsed jammers, ensuring system integrity in strong electromagnetic environments such as electrified railways.
-APME+: Advanced multipath estimation and suppression technology effectively reduces the impact of reflected signals from tunnel walls and viaducts, improving positioning accuracy.
-LOCK+: Maintains stable satellite signal tracking when trains experience vibrations caused by rail joints and switches, preventing loss of lock.
-IONO+: Mitigates the effects of ionospheric disturbances on signals, ensuring all-weather reliability.
-RAIM+: Receiver Autonomous Integrity Monitoring provides confidence metrics for positioning results to the train control system.
These technologies work together to achieve sustained, reliable RTK-INS positioning accuracy:
-Horizontal Accuracy: 0.6 cm + 0.5 ppm
-Vertical Accuracy: 1 cm + 1 ppm
-RTK Initialization Time: < 7 seconds
Integration Advantages of AsteRx-i3 D Pro in Rail Transit Vehicles
Compact Design Adapts to Various Rolling Stock Types
The AsteRx-i3 D Pro features a highly integrated single-board design, measuring only 47.5×70×10.5 mm and weighing 30 grams, allowing easy integration into various types of rolling stock such as high-speed trains, metro vehicles, and light rail. Its compact structure and low-power characteristics (full-frequency tracking power consumption of 1.2 watts) make it particularly suitable for rail vehicles with strict installation space and energy efficiency requirements.
Rich Interfaces Support Flexible Integration
The device is equipped with 4 high-speed serial ports (LVTTL), 1 USB device port, an Ethernet interface, and expandable connectors, supporting communication protocols such as TCP/IP and UDP. This multi-interface design enables seamless connection with train control systems, signaling systems, and dispatch centers.
Complete Protocol Stack Accelerates System Integration
The AsteRx-i3 D Pro fully supports industrial standard data formats including Septentrio Binary Format (SBP), NMEA 0183 (v3.01/v4.0), RTCM v2.x/v3.x (including MSM messages), and CMR v2.0. Combined with the configuration tools and development kits provided by Septentrio, it can significantly reduce system integration complexity.
Environmental Endurance Ensures Continuous Operation
The device operates within a temperature range of -40°C to +85°C and is certified to MIL-STD-810G vibration standards, as well as RoHS, WEEE, CE, FCC, and other certifications. This industrial-grade reliability design ensures stable performance under various climate conditions and vibration environments.
AsteRx-i3 D Pro: Building the Intelligent Positioning Foundation for Rail Transit
Centimeter-Level Positioning Enables Precise Operational Control
In high-speed rail and urban transit scenarios, the AsteRx-i3 D Pro delivers RTK-INS fusion positioning accuracy of 0.6 cm + 0.5 ppm horizontally and 1 cm + 1 ppm vertically. This centimeter-level precision provides a reliable positional reference for precise train stopping, autonomous driving, and operational control.
Full-Attitude Awareness Enhances Safe Operation
Through single-antenna output, it achieves full-attitude data including heading (0.2° in RTK mode) and pitch/roll angles (0.02°), providing critical attitude information for scenarios such as train curve negotiation and gradient operation, enhancing operational safety and ride comfort.
Anti-Interference Technology Ensures Signal Reliability
Integrated AIM+ anti-jamming and anti-spoofing technology suppresses various interference signals in rail transit environments; APME+ multipath suppression technology effectively handles reflective environments like tunnels and viaducts; LOCK+ technology ensures stable signal tracking for trains under vibration.
Inertial Dead Reckoning Achieves Seamless Positioning in Tunnel Sections
When a train enters GNSS-limited sections such as tunnels, the FUSE+ algorithm automatically switches to inertial dead reckoning mode. According to performance data, the horizontal error is only 0.106 meters within 5 seconds of a GNSS interruption and 3.006 meters within 30 seconds, ensuring that trains can maintain continuous and precise positioning even in long tunnels.
