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In my 15 years of experience working with inertial navigation systems, one thing I’ve learned is that IMU accuracy is critical to the success of many applications—whether you’re flying a drone, guiding a missile, or developing robotics. Without a clear understanding of an IMU’s accuracy, you’re left vulnerable to errors that could compromise your entire system. So, how accurate is an IMU? That depends on the type of sensor, its calibration, and the environment in which it operates. But let me give you some clear guidelines.
IMU accuracy depends largely on the grade of the sensor. Consumer-grade IMUs typically offer 10 to 100 degrees/hour precision, while industrial-grade IMUs improve this to 1 to 10 degrees/hour. Tactical-grade IMUs provide even better accuracy, ranging from 0.1 to 1 degree/hour, and are suited for military applications. Finally, navigational-grade IMUs offer the highest precision, with less than 0.01 degrees/hour, ideal for aerospace and defense.
Now, let’s dive into the details and look at how these accuracy levels apply across various applications.
Table of contents
Factors That Determine IMU Accuracy
IMU accuracy is determined by several key factors:
- Sensor Type and Grade: The IMU’s grade—whether it’s consumer, industrial, tactical, or navigational—is the most direct factor impacting accuracy. Higher-grade IMUs use more sophisticated technologies, like Fiber Optic Gyroscopes (FOG) or Ring Laser Gyroscopes (RLG), which significantly reduce drift and increase precision.
- Drift (Bias Instability): Drift refers to the gradual deviation in an IMU’s readings over time. The lower the drift, the more accurate the IMU. High-end IMUs, especially navigational-grade units, have extremely low drift rates compared to consumer and industrial models.
- Calibration: Even the most advanced IMUs require regular calibration to maintain accuracy. This process corrects for sensor imperfections, temperature effects, and other variables that can degrade performance.
- Environmental Factors: Temperature changes, mechanical shocks, and vibrations can introduce errors. Higher-grade IMUs are designed to compensate for these environmental challenges, while consumer and industrial units are more sensitive to such disruptions.
Understanding IMU Accuracy by Grade
IMUs are typically categorized into four primary grades, each with a different level of accuracy:
| IMU Grade | Gyroscope Bias Instability | Typical Applications |
|---|---|---|
| Consumer Grade | 10 to 100 degrees/hour | Smartphones, fitness trackers, basic gadgets |
| Industrial Grade | 1 to 10 degrees/hour | Industrial robots, drones, vehicles |
| Tactical Grade | 0.1 to 1 degree/hour | Military UAVs, ground vehicles, defense systems |
| Navigational Grade | <0.01 degrees/hour | Aircraft, submarines, spacecraft |
1. Consumer Grade IMUs
These are the simplest and most affordable IMUs, typically found in devices like smartphones, wearables, and gaming controllers. They offer accuracy levels ranging from 10 to 100 degrees/hour in terms of gyroscope bias instability. While sufficient for basic motion detection tasks, they are unsuitable for high-precision applications where drift and sensor noise can quickly lead to significant errors.
2. Industrial Grade IMUs
Industrial IMUs offer a noticeable improvement in accuracy, with drift rates between 1 and 10 degrees/hour. These are often used in autonomous vehicles, industrial robotics, and UAVs where moderate precision is needed, and where GPS may not always be available. These IMUs are designed to operate in moderately harsh environments but may still struggle with temperature fluctuations or prolonged operation in GPS-denied environments
3. Tactical Grade IMUs
Tactical IMUs are a step up, providing 0.1 to 1 degree/hour in terms of gyroscope bias stability. They are typically used in military vehicles, UAVs, and other high-performance systems where precise navigation is required, particularly in GPS-denied environments. With better performance in terms of both bias stability and resistance to environmental factors, these IMUs offer a good balance between cost and performance
4. Navigational Grade IMUs
At the top end, we have navigational-grade IMUs, which offer the highest precision, with bias instability below 0.01 degrees/hour. These are used in aircraft, submarines, and spacecraft—systems where even a small error can have significant consequences. Navigational-grade IMUs are capable of operating for extended periods in GPS-denied environments, making them ideal for long-term missions in aerospace and defense sectors. However, these IMUs are also the most expensive, often costing upwards of $100,000 per unit
How Does Sensor Type Affect IMU Accuracy?
Over the years, I’ve seen a wide range of IMU technologies evolve, and each has its role depending on the accuracy required. Here’s how I usually explain the main types of IMUs and their accuracy:
- MEMS IMUs (Micro-Electro-Mechanical Systems): MEMS IMUs have made great strides in the last decade. Early on, people viewed MEMS as lower-cost, less-accurate options, but that’s no longer entirely true. Today, there are high-end MEMS IMUs that can rival even some mid-tier FOG IMUs in accuracy, for example GuideNav’s GUIDE900 MEMS-Based IMU can provide gyro bias instability as precise as 0.1 degree/hour. In fact, I’ve worked with clients in UAVs and robotics who’ve found that MEMS IMUs provide the perfect balance of precision, size, and cost. They’re also incredibly durable and handle vibrations well, which is why they’re so widely used in drones and other mobile systems.
- FOG IMUs (Fiber Optic Gyroscope): If you need more accuracy and stability, FOG IMUs are the way to go. I’ve worked with these in aerospace and defense projects, where precision is everything. FOG sensors offer excellent long-term stability with very low drift, making them ideal for applications where even small navigation errors could lead to major issues. FOG IMUs are commonly found in aircraft and missiles, and while they’re pricier, the accuracy they offer is unmatched by most other technologies in these environments.
- RLG IMUs (Ring Laser Gyroscope): These are the top of the line when it comes to accuracy. If you’re working in high-stakes areas like military submarines or space navigation, RLG IMUs are your best bet. They offer the highest accuracy with virtually no drift, but they come at a high cost and are relatively bulky. I’ve seen them used in applications where long-term precision is non-negotiable, and they rarely, if ever, disappoint.
Why Drift Matters for IMU Accuracy？
No matter how advanced the IMU is, drift remains a challenge, particularly in long-term navigation without external reference points like GPS. Drift, also known as bias instability, is the slow accumulation of error in an IMU’s readings over time. This error is particularly significant in applications like autonomous navigation or missile guidance, where even a small deviation can lead to failure.
For example, navigational-grade IMUs have drift rates as low as 0.01 degrees/hour, which means they can maintain precise orientation data over long periods. In contrast, consumer-grade IMUs with drift rates of up to 100 degrees/hour can quickly become unreliable in such critical tasks.
The Role of Calibration and Sensor Fusion
Even the most accurate IMUs require regular calibration to ensure their performance remains reliable over time. Calibration helps adjust for sensor drift, temperature changes, and mechanical wear. Without proper calibration, even a high-end IMU can experience degraded performance.
In many systems, sensor fusion is used to further improve accuracy. By combining IMU data with other sensors, like GPS or magnetometers, you can correct for drift and improve overall system reliability. This is particularly common in high-performance applications like autonomous vehicles or missile systems, where redundancy and precision are critical.
How GuideNav Can Help
At GuideNav, we offer a full range of IMU sensors, spanning across all precision levels—from industrial to tactical, and navigational-grade. Whether your application requires motion tracking or high-precision navigation in critical environments, we have the right IMU to meet your needs.
Our products are renowned for their high accuracy and reliability. We offer a variety of features to mitigate common IMU challenges, including:
- Sophisticated calibration techniques that minimize drift and ensure stable performance.
- Powerful software designed to suppress noise and boost the precision of IMU data.
- Comprehensive guides and expert support to help users fully utilize their IMUs’ capabilities.
GuideNav is an excellent starting point if you’re in search of the ideal IMU for your needs.
