SKM2505NRD-40MXT Dual-Band RTK INS High-Precision GNSS Module (Gmouse)

2026-05-18/ By Admin

In urban canyons, underground parking garages, long tunnels, and other environments where satellite signals are weak or completely lost, traditional vehicle navigation often suffers from position drift, speed jumps, and heading confusion. For professional applications such as autonomous driving test vehicles, high-definition mapping vehicles, public transit dispatching, and precision agriculture, this "loss of signal" not only degrades user experience but can also cause complete system failure. How can vehicles achieve continuous, reliable high-precision positioning in any scenario? The SKM2505NRD-40MXT dual-band RTK INS high-precision Gmouse provides a compelling answer: it deeply integrates L1+L5 dual-band RTK positioning with inertial navigation technology. Even without any odometer signal, it can independently output centimeter-level position, velocity, and attitude information for extended periods after satellite signal loss, achieving truly "all-weather, all-scenario" high-reliability navigation.

1. Three Major Pain Points of Traditional Vehicle Navigation in Complex Environments

• Failure upon satellite signal loss: In tunnels, underground garages, dense tree-lined roads, etc., GNSS signals are completely interrupted, causing pure satellite positioning modules to immediately lose position updates, leading to navigation stalls or severe drift.
• Insufficient heading accuracy: When the vehicle is moving at low speed or stationary, GNSS alone cannot accurately determine direction, causing confusion in the vehicle's heading on the map and affecting route guidance.
• Dependence on external sensors: Many so-called "INS" solutions require connection to the vehicle's odometer signal, which complicates aftermarket wiring and raises safety concerns, hindering adoption.

The SKM2505NRD-40MXT completely eliminates the need for odometer integration through dual-band RTK + high-performance MEMS inertial sensors + adaptive Kalman filtering, significantly improving positioning continuity in weak-signal and no-signal environments.

2. Core Advantages: Deep Fusion of Dual-Band RTK and Odometer-Free INS

2.1 L1+L5 Dual-Band RTK – Centimeter-Level Accuracy in Open Areas

The module integrates a high-sensitivity dual-band GNSS receiver supporting GPS L1/L5, BeiDou B1I/B2a, Galileo E1/E5a, QZSS L1/L5, and includes a built-in dual-band high-precision antenna. In RTK mode with differential data input, it achieves horizontal positioning accuracy of ≤1 cm + 1 ppm, meeting the stringent requirements of high-precision mapping, autonomous driving, and precision agriculture.

2.2 High-Performance 6-Axis IMU – Pure Inertial Navigation Without Odometer

The module integrates a 3-axis gyroscope and 3-axis accelerometer, with factory calibration for orthogonal errors, temperature drift, and other biases. When GNSS signals are completely lost (e.g., entering a tunnel), the system automatically switches to pure inertial navigation mode. Without any external odometer signal, it continues to output position, velocity, pitch/roll/heading angles for extended periods using only its own inertial solution. Real-world test data shows: within 120 seconds of GNSS loss, horizontal position error is approx. 60 meters, horizontal velocity error 0.5 m/s, and heading error 2.0 degrees – a leading performance among similar global products.

2.3 Adaptive Integrated Navigation Algorithm – Intelligent Fusion of GNSS and INS

Based on an Extended Kalman Filter (EKF) tightly coupled architecture, the system evaluates GNSS signal quality in real time and dynamically adjusts the weighting between satellite and inertial data. In open areas, it fully trusts GNSS; in partially obstructed areas, it increases INS weighting; and during complete signal loss, it relies entirely on INS. The algorithm also detects and rejects GNSS data with significant errors (e.g., multipath reflections), effectively suppressing position jumps and drift.

2.4 Zero-Velocity Update and Anti-Vibration Design – No Drift When Stationary

For stop-and-go scenarios such as traffic lights or jams, the algorithm detects zero-velocity states via the accelerometer and corrects velocity integration errors to prevent position drift. Additionally, adaptive filtering effectively removes high-frequency vibration accelerations during driving, ensuring smooth velocity and attitude outputs.

2.5 No Installation Angle Restriction – Peel-and-Stick for Aftermarket

The module features a compact, integrated design (built-in antenna and IMU) and can be mounted at any angle on the roof or near the dashboard. After power-up, a static period of 5–10 seconds completes attitude initialization; then a few minutes of normal driving (including acceleration, deceleration, and turns) enables automatic installation angle recognition and calibration. It adapts to cars, trucks, buses, agricultural machinery, etc.

2.6 Plug-and-Play with Standard NMEA0183 Output

The module provides a UART interface with RS232 levels, default baud rate 115200, outputting standard NMEA0183 sentences (including GGA, RMC, GSV, etc.). It also outputs extended sentences:

• $PAIRMSG,90* – INS status (0=unknown, 1=initializing, 2=coarse, 3=stable)
• $PAIRMSG,91* – dynamic status and driving behavior alerts (e.g., hard acceleration, hard braking, sharp turning, collision)
  Users can directly connect the module to a vehicle host or T-BOX without developing complex algorithms.

3. Typical Applications and Field Test Results

Bus & Passenger Vehicle High-Precision Navigation

Urban buses frequently travel under viaducts, tree-lined roads, and tunnels. Field tests in Shenzhen’s Henglongshan Tunnel and an underground garage show that after 100 meters of pure inertial navigation, the error is only 1–2 meters – perfectly solving the "lose signal in tunnels" problem.

Autonomous Driving & HD Mapping

RTK centimeter-level positioning meets lane-level guidance requirements, while INS fills in signal gaps in urban canyons, ensuring continuous, complete trajectories for mapping vehicles.

Precision Agriculture

Mounted on tractors or harvesters, the module continues positioning with INS in areas where RTK signal is weak (e.g., field edges), achieving row spacing errors <5 cm.

Vehicle Telematics & UBI Insurance

Real-time acquisition of vehicle position, velocity, acceleration, and yaw rate enables driving behavior analysis (hard acceleration/braking/turning), providing data support for fleet management and usage-based insurance pricing.

4. Technical Specifications

The SKM2505NRD-40MXT is an all‑in‑one terminal integrating a dual‑band high‑precision GNSS antenna and an IMU.

• Interface: Micro-Fit 3.0 (power, GND, TXD, RXD)
• Supply voltage: 3.5V – 5.5V (recommended 5V), operating current ≥150 mA
• Cable length options: 3 m, 5 m, 8 m
• Operating temperature: -40℃ to +85℃
• GNSS support: GPS L1/L5, BeiDou B1I/B2a, Galileo E1/E5a, QZSS L1/L5
• Time to first fix (cold start): 28 s; hot start: 1 s; reacquisition: 1 s
• Tracking sensitivity: -165 dBm
• RTK fixed solution horizontal accuracy: 1 cm + 1 ppm
• PPS accuracy: 20 ns
• IMU: High-performance 3‑axis gyroscope and 3‑axis accelerometer, fully factory‑calibrated for bias, scale factor, misalignment, and temperature drift.
• Performance without odometer (GNSS loss):
  • 60 s loss: horizontal position error 25 m
  • 120 s loss: horizontal position error 60 m, horizontal velocity error 0.5 m/s, pitch/roll error 1.0°, heading error 2.0°
• Zero-velocity update: Supported
• Automatic installation angle recognition: Supported
• Data rate: Default 1 Hz, configurable up to 10 Hz
• Output protocols: Standard NMEA0183 + proprietary $PAIRMSG sentences
• Anti‑counterfeiting: Each unit has unique calibration parameters

5. Why Choose the SKM2505NRD-40MXT?

• Truly odometer‑free: Eliminates the most troublesome wiring issue in aftermarket installations, reducing complexity and safety risks.
• High integration: Antenna, RTK receiver, and IMU in one compact unit – peel and stick.
• Proven algorithms: Based on years of MEMS inertial research and adaptive filtering, validated through extensive real‑vehicle testing with excellent anti‑drift and continuous navigation performance.
• Flexible adaptability: Supports RTCM 2.3–3.3 differential input, connects to CORS or self‑built base stations; custom baud rates and output sentences available.

No more fear of tunnels and skyscrapers – empower every vehicle with navigation that never gets lost.

The SKM2505NRD-40MXT dual‑band RTK INS high‑precision Gmouse redefines the reliability of vehicle navigation through integrated positioning technology. It allows autonomous driving test vehicles to maintain lane‑level positioning in long tunnels, prevents bus position jumps under viaducts, and enables precision agricultural machinery to continue working at field edges. Choose it – choose a positioning confidence without blind spots.