Drones Altimeters Precision: A Look
In the world of drone technology, maintaining accurate altitude measurements is crucial for various applications, from aerial mapping to precision agriculture. This article delves into the three primary systems drones use to measure altitude and discusses the importance of calibration and ground control points.
Infrared Altimeters: Precision at Short Ranges
Infrared altimeters, which work by emitting infrared light downwards and measuring the time or intensity of the reflected light from the ground, excel at precise, short-range height measurement. They are commonly found in sensors integrated with drones for precise landing or obstacle avoidance, offering accuracy down to centimeters at low altitudes. However, their accuracy degrades with distance and surface reflectivity.
Barometric Altimeters: Mid-Range Accuracy
Barometric altimeters, which measure altitude by sensing ambient air pressure, provide mid-range altitude data with typical accuracy around ±1-3 meters. They are standard in drones for general altitude measurement due to their lightweight and energy-efficient nature. While environmental factors like temperature and weather can affect readings slightly, barometric sensors are a reliable choice for drone altitude measurements.
GPS Altimeters: Global Positioning
GPS-based altitude measurement uses signals from satellites to determine the drone’s position in 3D space, including elevation. GPS altitude accuracy is generally lower than horizontal position accuracy, with errors often around ±3 to ±10 meters under normal consumer conditions. However, using augmentation systems like GNSS (GPS, GLONASS, BeiDou) can improve this somewhat but rarely matches barometric precision for altitude.
Combining Systems for Enhanced Reliability
In practice, drones often combine these systems for better reliability and accuracy, using barometric measurements for altitude control with GPS providing redundancy and positioning context. For example, drone-based LiDAR systems, which also incorporate GPS (GNSS) antennas for georeferencing, achieve vertical accuracies on the order of centimeters.
Calibration and Maintenance
Calibration is essential when moving the drone to a different altitude of more than 1000 feet, after a firmware update, and following a nasty crash. Periodic IMU calibration is recommended for all drone users to ensure accurate altitude readings. Signs of uncalibrated sensors include being unable to hold a stable hover or the altitude reading not going back to zero when the drone lands at the same take-off spot.
Altitude Restrictions and Applications
For casual use, a few feet of altitude drift is generally acceptable, and doing basic IMU calibration should be enough. However, for mapping applications requiring centimeter-level locational accuracy, established data correction protocols such as GCPs or ground stations are essential. Drone flight in areas of controlled airspace is typically restricted to altitudes below 400 feet AGL to avoid interfering with manned aircraft operations.
Conclusion
Understanding the principles behind the three altitude measuring systems in drones—infrared, barometric, and GPS—helps drone operators make informed decisions about their equipment and maintain accurate altitude measurements for optimal performance. By following best practices for calibration and data correction, drone users can ensure their devices deliver the precision and reliability needed for a wide range of applications.
Drone operators often rely on a combination of infrared, barometric, and GPS altitude measuring systems for enhanced reliability and accuracy, with infrared excelling at short-range precision, barometric providing mid-range accuracy, and GPS offering global positioning.
Periodic IMU calibration is essential to ensure accurate altitude readings and drone stability, particularly in applications requiring centimeter-level locational accuracy, such as mapping and LiDAR systems.
