What is ASIL B Grade GNSS?

In advanced vehicles and autonomous machines, accuracy alone is not enough – safety is equally paramount. Imagine an autonomous car that knows its position down to the centimeter but cannot reliably detect if its positioning system malfunctions; such a failure could lead to hazardous situations. This is why the concept of “ASIL B Grade GNSS” has garnered so much attention. It represents the merging of high-precision GNSS positioning with stringent automotive safety standards. In industries where every centimeter – and every decision – counts, from self-driving tractors in agriculture to unmanned drones in the skies, ASIL B grade GNSS ensures that positioning data is not only precise, but also delivered with a level of reliability and integrity suitable for safety-critical applications. SWEGEO is at the forefront of implementing these standards in GNSS solutions, enabling applications that demand both pinpoint accuracy and unwavering safety assurances.

Understanding Automotive Safety Integrity Levels (ASIL): ASIL stands for Automotive Safety Integrity Level, a classification system defined by the ISO 26262 standard for functional safety in road vehicles. The purpose of ISO 26262 and ASIL ratings is to systematically gauge how much rigor and risk reduction is needed in the design of automotive electronics or software components, based on the potential hazards they pose. There are four main ASIL levels – A, B, C, and D – with ASIL A being the lowest safety integrity requirement and ASIL D being the highest. Determining an ASIL for a given component involves analyzing the potential harm that could result from its failure (severity), how frequently the situation leading to that harm might occur (exposure), and how controllable that situation would be if it occurred (controllability). For example, a system whose failure could lead to a minor inconvenience would be ASIL A or even “QM” (Quality Management, meaning no special safety requirement), whereas a failure that could directly lead to loss of life if not properly handled might require ASIL D.

What ASIL B Means: ASIL B indicates a moderate-to-high level of risk reduction is required. In simpler terms, a component that is classified as ASIL B is one where a malfunction could potentially cause significant issues or danger, but the overall hazard level is not as extreme as those requiring the top-tier (ASIL D) measures. For instance, many driver-assistance features and some braking or steering control systems in vehicles are designed to meet ASIL B requirements. This means that while a failure in such systems is not expected to be life-threatening in all cases (as might be assumed for ASIL D scenarios), it still presents enough risk that robust safety measures must be in place.

In the context of a GNSS receiver or positioning system, an ASIL B grade GNSS implies that the device and its software have been developed and evaluated with processes that satisfy ASIL B safety objectives. The GNSS receiver is expected to achieve a certain level of reliability and to detect or handle certain failures internally. It’s not just about preventing failure – it’s also about defining how the system behaves if something goes wrong. ASIL B design might require, for example, that the GNSS module can detect if its calculated position is becoming unreliable or if there’s an internal fault, and then alert the rest of the system or enter a safe state. This could involve internal self-checks, redundancy in critical components, or fail-safe mechanisms that ensure any error does not propagate to cause a dangerous action by the robot or vehicle that relies on that data.

Safety and Precision Go Hand in Hand: One of the misconceptions might be that adding safety constraints (like those required for ASIL B) could compromise performance or precision – but in modern ASIL B GNSS solutions, that’s not the case. Manufacturers like SWEGEO have demonstrated that you can have both extremely accurate positioning and the peace of mind that comes with built-in safety integrity. In practice, achieving ASIL B compliance in a GNSS device means implementing features such as:

• Integrity Monitoring: The GNSS receiver continuously assesses the trustworthiness of its own output. If the satellite signals are being spoofed or if a calculation fault occurs, the system can detect that something is off. It might use algorithms to compare multiple signal sources or check consistency over time. If the integrity check fails (meaning the position data might be wrong), the device can flag this condition immediately.
• Fault Detection and Diagnostics: ASIL B designs include comprehensive diagnostic checks. This can range from simple checksums and memory tests inside the GNSS firmware to more elaborate cross-verification like dual-core calculations (where two processors compute position in parallel and cross-verify results). The goal is to catch hardware or software faults before they result in incorrect position outputs. If a fault is detected, an ASIL B GNSS module might suppress its outputs or send an error flag instead of risking a false reading.
• Fail-Safe and Redundancy: In some cases, achieving ASIL B may involve redundant elements or backup systems. For example, a GNSS positioning system might be paired with an inertial measurement unit (IMU) such that if GNSS signals are lost or deemed unreliable, the system can fall back to inertial navigation for a short period. While the IMU alone might drift over time, for the moment it can act as a safety net, providing continuity in position information until GNSS data is trustworthy again. The transition between these sources is managed carefully to maintain overall reliability of the navigation solution.
• Automotive-Grade Quality: Hardware components and electronics in an ASIL B GNSS device are typically automotive grade, meaning they can withstand harsh conditions (temperature extremes, vibration, electromagnetic interference) over long periods. This durability contributes to safety by reducing the chance of an environmental condition causing a failure. Additionally, the development process for ASIL B mandates thorough testing, validation, and documentation. Every scenario that could reasonably lead to a hazard is analyzed and mitigated if possible.

Applications Requiring ASIL B Grade GNSS: High-integrity positioning isn’t necessary for every GPS tracker or navigation gadget, but it becomes critical in certain applications where position errors or system failures could lead to accidents or significant losses. Some key examples include:

• Autonomous Tractors and Agricultural Machinery: Modern farming equipment often drives itself using GNSS-based auto-steering. If a tractor’s positioning were to fail or give incorrect data while navigating a field, it might veer off course, potentially damaging crops, equipment, or even endangering nearby workers. ASIL B grade GNSS in this context ensures that the tractor’s navigation system has multiple safeguards. It will reliably follow the planned paths and if anything goes awry (like a signal integrity issue), the system knows to slow down or stop rather than plow ahead blindly.
• Fleet and Logistics Management: Truck fleets that employ autonomous or highly automated driving features require consistent and safe positioning. On highways or busy routes, a truck’s navigation system failing could mean it doesn’t keep its lane properly or misses a critical turn. ASIL B compliance means the GNSS in these trucks has layers of protection so that the chance of a dangerous positioning error is extremely low. Even for non-autonomous fleet vehicles, high-integrity GNSS can improve safety by providing more reliable data for driver-assist systems.
• Autonomous Drones and UAVs: Drones are increasingly used for deliveries, inspections, and aerial surveys. A drone malfunction due to GPS errors could result in a crash, which is dangerous particularly if it’s operating in urban or populated areas. An ASIL B grade GNSS in a drone ensures that the drone’s autopilot receives trusted location information. If the GPS fix becomes uncertain, an ASIL B system can trigger the drone to enter a fail-safe mode (such as hovering in place or slowly descending) instead of continuing on possibly incorrect coordinates. This is crucial for meeting emerging safety regulations for unmanned aircraft.
• Advanced Driver-Assistance Systems (ADAS) and Autonomous Vehicles: Self-driving cars and even many modern cars with ADAS features rely on precise positioning data. For example, automated lane-keeping or highway autopilot functions might use high-definition maps coupled with GNSS to know exactly where the vehicle is in a lane. If that positioning were to become faulty, the car could drift or make incorrect decisions. Therefore, the GNSS units in such systems are designed to ASIL B or higher standards. They provide the car’s central computer with not just coordinates, but also an estimate of confidence and alerts if the data cannot be trusted. In a scenario where something is wrong (say, GPS signals are compromised or reflections cause multi-path errors), the system would ideally disengage automated control and hand back to the human driver or switch to a safe mode.

In all these applications, ASIL B GNSS technology is not just about knowing where something is, but ensuring that the “where” is correct and dependable. It is about having the system itself be smart enough to recognize its limits and failures – a cornerstone of any safety-critical design.