Stellar-40 Tactical-grade inertial navigation system

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Dead reckoning is a method of navigating without GNSS signals by relying on inertia and other sensor data to maintain continuous tracking. Usually, when GNSS is lost, a system loses its position entirely. With dead reckoning, the system calculates a continuous position that will slowly drift over time. The rate of this drift depends on the quality of the internal IMU and the availability of external aiding sensors.

The Stellar-40 uses our proprietary sbgECom protocol, which utilizes clearly defined message frames. Using those predefined messages, the system can seamlessly ingest airdata, body velocities, and absolute position data from any external sensor capable of providing that information.

No, as it is not required. The Stellar-40’s advanced sensor fusion algorithm automatically calculates and estimates wind conditions in real-time, eliminating the need for you to input it manually.

For land platforms, the Stellar-40 supports a variety of aiding inputs to improve navigation accuracy, especially in GNSS-denied environments. These include hardware odometers (wheel odometry), velocity aidings from external sensors (such as LiDAR or optical sensors), and absolute position aidings.

The right choice depends on your operating environment. We highly recommend the damped version for platforms exposed to harsh, vibrating environments, such as deep strike drones or Unmanned Ground Vehicles (UGVs). If you are unsure which version suits your application, our support team is ready to help you make the right choice.

What is SBAS ?

Satellite-Based Augmentation System (SBAS) is a GNSS augmentation technology that improves the accuracy, integrity, availability, and continuity of satellite positioning. Initially developed to support aviation, SBAS has become a valuable navigation aid for applications such as UAVs, marine navigation, precision agriculture, GIS mapping, autonomous vehicles, and inertial navigation systems (INS). Unlike Real-Time Kinematic (RTK) or Precise Point Positioning (PPP), SBAS provides free meter-level positioning without requiring a local base station or an Internet connection.

A standalone GNSS receiver determines its position by measuring pseudoranges from satellites belonging to constellations such as GPS, Galileo, GLONASS, or BeiDou. However, these measurements are affected by several error sources, including satellite clock drift, orbit (ephemeris) errors, ionospheric delay, tropospheric delay, receiver noise, and multipath. SBAS continuously estimates the largest of these errors and broadcasts real-time corrections that significantly improve the navigation solution.

The SBAS architecture relies on a network of precisely surveyed reference stations distributed across a region. These stations continuously monitor GNSS signals and compare the measured satellite ranges with their known positions to estimate satellite clock, orbit, and ionospheric errors. The measurements are transmitted to master control centers, which combine data from all reference stations to generate correction messages and integrity information. These messages are then uplinked to geostationary satellites that rebroadcast them to SBAS-enabled GNSS receivers. The receiver applies the corrections before computing its position, effectively reducing the dominant error sources affecting the pseudorange measurements.

Mathematically, the corrected pseudorange can be expressed as:

Pcorrected​ = Pmeasured​ − Δclock ​− Δorbit​ − Δiono​

where Pmeasured is the original pseudorange measurement, Δclock represents the satellite clock correction, Δorbit​ is the orbital correction, and Δiono is the ionospheric delay correction.

These corrections typically reduce standalone GNSS horizontal positioning errors from approximately 3–10 meters to around 1–2 meters. Although this level of accuracy is lower than the centimeter-level performance achieved with RTK or PPP, SBAS offers a major advantage: integrity monitoring. Rather than simply improving position accuracy, SBAS continuously evaluates the health of every monitored satellite and rapidly alerts users if a satellite becomes unreliable because of clock anomalies, orbital errors, or signal degradation. This capability is essential for safety-critical applications where users must know whether the navigation solution can be trusted.

Several regional SBAS services operate around the world. These include WAAS in North America, EGNOS in Europe, MSAS in Japan, GAGAN in India, SDCM in Russia, KASS in South Korea, and SouthPAN in Australia and New Zealand. Modern multi-frequency GNSS receivers generally support multiple SBAS services automatically, depending on their geographic location.

For inertial navigation systems, SBAS provides a more accurate and reliable GNSS reference that improves sensor fusion performance. An Extended Kalman Filter (EKF) uses the corrected GNSS position and velocity measurements to periodically bound the drift accumulated by the inertial sensors. Compared with standalone GNSS, SBAS reduces measurement noise and satellite-related biases, resulting in more stable position and velocity updates while providing valuable integrity information for navigation algorithms. However, SBAS does not increase the GNSS update rate and cannot compensate for GNSS outages. During signal interruptions, overall navigation performance still depends primarily on the quality of the IMU and the effectiveness of the INS estimation algorithm.

SBAS is therefore an excellent solution for applications requiring free, globally available meter-level positioning with high reliability and integrity. It is particularly well suited for autonomous vehicles, UAVs, marine navigation, agriculture, and industrial systems where robust navigation is more important than achieving centimeter-level accuracy. When applications demand survey-grade positioning, RTK or PPP remain the preferred correction techniques, while SBAS serves as a dependable and widely available enhancement to conventional GNSS navigation.