GUIDANCE FOR IMU USAGE IN LIDAR APPLICATIONS
IMUs are used to enhance the accuracy and stability of 3D point cloud data by ensuring the scan data is oriented correctly to account for environmental factors (vibrations, shifts, slippage…). IMUs are sometimes needed even if the LiDAR is mounted to a stationary object, because even small vibrations can introduce noise that is problematic for sensitive applications.
IMU RECOMMENDATIONS BY USE CASE
| Application | Needs An IMU? | Purpose |
|---|---|---|
| Terrestrial Surveying | Yes (Recommended) | To correct for tripod vibration/tilting |
| Indoor Mapping | Yes (Highly Recommended) | To align scans, even if moving slowly |
| Industrial Inspection | Depends on use case | Optional if mounted on a high-precision, stable robot arm |
| Collision Avoidance | No | 2D LIDAR for basic obstacle detection |
| Autonomous Navigation | Yes | To account for vibration, slippage, and slopes |
| Stationary Applications | Depends on use case | See table below for details |
INTEGRATED VS EXTERNAL IMU
| Question | If YES | If NO |
|---|---|---|
| Does the platform move faster than walking speed? | External IMU | Integrated IMU |
| Is SLAM required? | External IMU | Integrated IMU |
| Is GNSS involved? | External IMU | Integrated IMU |
| Do you need pose accuracy over minutes or hours? | External IMU | Integrated IMU |
| Is this a cost-sensitive deployment? | Integrated IMU | External IMU |
| Is time-to-market critical? | Integrated IMU | External IMU |
| Do you control the full sensor fusion stack? | External IMU | Integrated IMU |
IMUs IN STATIONARY LIDAR APPLICATIONS
A stationary LiDAR sensor does not technically require an Inertial Measurement Unit (IMU) to function, as its primary job is to measure distances using laser pulses. However, an IMU is highly recommended for stationary applications to ensure the data is correctly oriented and to correct for vibrations or accidental shifts.
Here is a breakdown of why an IMU might or might not be used in a stationary setup:
When a Stationary LiDAR Needs an IMU
- Vibration Correction: Even if a scanner is “stationary” (e.g., on a tripod on a busy street or on a robotic arm), minor vibrations or subtle movements can cause misalignment in the 3D point cloud.
- Orientation Mapping: An IMU enables the scanner to know “which way is up,” allowing it to automatically orient the point cloud in 3D space.
- Tilt Monitoring: If the tripod settles or tilts slightly, an IMU can detect this, ensuring the scan is not distorted.
- Stop-and-Go Scanning: In techniques where a sensor is moved, stopped, and scanned, an IMU helps maintain a consistent coordinate system.
When a Stationary LiDAR Does Not Need an IMU
- Rigid, Stable Environments: In a completely vibration-free, perfectly stable environment (like a robotic inspection cell in a factory), the device’s own internal leveling systems or manual alignment may be sufficient.
- Basic Proximity Sensing: For simple 2D collision avoidance or basic obstacle detection, an IMU is unnecessary.
| Application | Motion Profile | Accuracy Sensitivity | Recommended IMU | Rationale |
|---|---|---|---|---|
| Smart Intersections / ITS | Static | Low–Medium | Integrated IMU | Object detection only; ego-motion irrelevant |
| Traffic Analytics (speed, counts) | Static | Medium | Integrated IMU | Stable mounting, minimal drift |
| Warehouse Automation (AMRs) | Slow / Smooth | Medium | Integrated IMU | Cost + simplicity wins |
| Warehouse SLAM (high-density racks) | Moderate | High | External IMU | Drift accumulates indoors |
| Mobile Mapping (vehicles) | Fast | Very High | External IMU | Survey-grade pose required |
| Mining / Construction Equipment | Heavy vibration | High | External IMU | MEMS IMUs struggle with vibration |
| Agriculture (tractors, sprayers) | Moderate / uneven | High | External IMU | Long runs + GNSS dropouts |
| Autonomous Vehicles | High dynamics | Critical | External IMU | Safety-critical pose estimation |
| Robotics (R&D / labs) | Variable | Medium–High | Depends | Budget vs accuracy trade |
| Fixed Security / Perimeter | Static | Low | Integrated IMU | Orientation only |
| Drones / UAVs | High dynamics | Critical | External IMU | Integrated IMUs not sufficient |