Robust Normal Estimation for Sparse LiDAR Scans

Core Concepts

A method for fast and robust normal estimation from sparse LiDAR data by clustering points based on the angles of connecting line segments to avoid estimating normals across different surfaces.

Abstract

The paper presents a method for estimating surface normals from sparse LiDAR data in a robust manner. Mechanical LiDAR sensors produce sparse data, where neighboring points may not belong to the same underlying surface, leading to issues with typical normal estimation approaches. The key contributions are: The authors leverage the organized structure of LiDAR data to cluster points based on the angles of the line segments connecting neighboring points. This allows them to identify points that likely belong to the same planar surface and compute normals only within these clusters. The authors show that their method produces more robust normals, especially in high-curvature areas, compared to a baseline normal estimation approach. This is demonstrated through visual inspection of reconstructed maps and improved performance in a SLAM system. The authors show that their method only incurs a constant-factor runtime overhead compared to the baseline, making it suitable for computationally-constrained environments. The paper first describes the baseline normal estimation approach, then details the authors' method of clustering points based on line segment angles and using these clusters to compute normals. Experimental results on both self-recorded and public datasets validate the claims of improved robustness and efficiency.

Stats

The paper reports the following key statistics: The average runtime and standard deviation for computing normals using the proposed method and the baseline method on 16-beam and 32-beam LiDAR data. For 16-beam LiDAR data, the proposed method takes 1.02 ms ± 0.14 ms, while the baseline takes 0.56 ms ± 0.02 ms. For 32-beam LiDAR data, the proposed method takes 2.54 ms ± 0.61 ms, while the baseline takes 1.3 ms ± 0.26 ms.

Quotes

"The main contribution of this paper is a method that improves upon the baseline normal computation technique by clustering the points stemming from neighboring lasers into components likely describing the same underlying surface and computing the normals within the clusters of these points, avoiding cross-surface normal computation." "We show that using our method for normal estimation leads to normals that are more robust in areas with high curvature which leads to maps of higher quality." "We also show that our method only incurs a constant factor runtime overhead with respect to a lightweight baseline normal estimation procedure and is therefore suited for operation in computationally demanding environments."

Key Insights Distilled From

Fast and Robust Normal Estimation for Sparse LiDAR Scans

by Igor Bogosla... at arxiv.org 04-23-2024

https://arxiv.org/pdf/2404.14281.pdf

Deeper Inquiries

How would the proposed method perform on highly irregular or complex environments with many small, disconnected surfaces

The proposed method for normal estimation in sparse LiDAR data, as outlined in the context above, would likely perform well in highly irregular or complex environments with many small, disconnected surfaces. This is because the method leverages the structured nature of the data produced by LiDAR sensors and clusters points based on the underlying surface they belong to. By separating points into connected components that likely describe the same underlying surface, the method can handle scenarios where there are numerous small surfaces or discontinuities in the environment. This approach helps in avoiding estimating normals across different surfaces, leading to more accurate and robust normal estimation, even in complex environments.

What other techniques could be explored to further improve the robustness of normal estimation in sparse LiDAR data without significantly impacting runtime

To further improve the robustness of normal estimation in sparse LiDAR data without significantly impacting runtime, several techniques could be explored: Adaptive Neighborhood Selection: Instead of using a fixed neighborhood size for normal estimation, an adaptive approach could be implemented. This method would dynamically adjust the neighborhood size based on the local point density, curvature, or other relevant features. By adapting the neighborhood size, the method can better capture the underlying surface geometry, especially in areas with varying point densities. Outlier Rejection: Incorporating outlier rejection techniques can enhance the robustness of normal estimation. By identifying and excluding outliers or noisy points from the estimation process, the method can produce more accurate normals, particularly in regions with sparse or noisy data. Multi-Scale Analysis: Implementing a multi-scale analysis approach can improve the overall robustness of normal estimation. By considering normals at different scales or resolutions, the method can capture fine details in areas with high curvature while maintaining efficiency in computation. Integration of Machine Learning: Utilizing machine learning algorithms, such as neural networks, for normal estimation can enhance the method's ability to learn complex patterns and relationships in the data. By training the model on diverse datasets, the method can improve its generalization capabilities and robustness in various environments.

How could the insights from this work on normal estimation be applied to other tasks in robotics and perception that rely on accurate surface information, such as object segmentation or scene understanding

The insights gained from this work on normal estimation in sparse LiDAR data can be applied to various tasks in robotics and perception that rely on accurate surface information, such as object segmentation or scene understanding. Some potential applications include: Object Segmentation: The accurate estimation of surface normals is crucial for object segmentation tasks, especially in cluttered or complex environments. By leveraging the proposed method's ability to compute robust normals, object boundaries can be more accurately delineated, leading to improved segmentation results. Scene Understanding: In tasks related to scene understanding, such as semantic mapping or environment modeling, precise surface information is essential. By integrating the insights from this work, robots or autonomous systems can better understand the spatial layout of their surroundings, differentiate between different surfaces, and make informed decisions based on the scene's geometry. Obstacle Detection and Avoidance: Accurate surface normals play a vital role in obstacle detection and avoidance systems. By applying the proposed method for normal estimation, robots can better perceive and navigate through complex environments, identifying obstacles with greater precision and planning optimal paths to avoid collisions. Overall, the advancements in normal estimation presented in this work can significantly benefit a wide range of robotics and perception tasks, enhancing the overall performance and reliability of autonomous systems in various real-world scenarios.