双阈值法地面激光点云强度图像边缘提取

Dual-threshold Algorithm for Intensity Image Edge Extraction of Terrestrial Laser Scanning Point Cloud

摘要:

在扩展目标激光测距方程的基础上，根据扫描仪的辐射机制，分析了利用强度图像进行点云边缘提取的可行性及强度图像中非边缘点、边缘点及噪声点的八邻域特征。根据各类点的八邻域特征，提出了一种双阈值判别准则，用于提取强度图像中的非边缘点、边缘点与噪声点。根据判别结果：对非边缘点与噪声点进行中值滤波；对边缘点，其灰度值保持不变。最后利用Canny算子对滤波后的强度图像进行边缘提取，并通过实验对该方法进行了验证，对不同的双阈值选取结果进行了讨论分析。实验结果表明：利用原始激光强度图像可有效实现地面激光点云的边缘提取，双阈值法不仅能去除点云强度图像中的椒盐噪声，同时能保证边缘提取的精度。

关键词:地面三维激光扫描;激光测距方程;点云强度噪声;强度图像;边缘提取

Abstract:

Based on the laser range equation for the extended Lambertian targets and the radiometric principles of laser scanners, the feasibility of original intensity image edge extraction is demonstrated, along with the eight neighborhood characteristics of non-edge points, edge points and noise points. By utilizing the eight neighborhood characteristics, a new dual-threshold criterion is proposed to distinguish and extract different points. According to the judgment results, the median filter algorithm is applied to filter the non-edge points and noise points, while for the edge points, their gray values keep unchanged. Finally, edge extraction is conducted by adopting the “Canny” algorithm. The proposed method is verified through actual experiment and the results of different dual-thresholds are discussed and analyzed. The results reveal that edge extraction can be effectively conducted on the raw intensity image, and the proposed approach can remove the salt and pepper noise of the intensity image as well as ensure the accuracy of edge extraction.

Key words:terrestrial laser scanning; laser range equation; intensity noise of point cloud; intensity image; edge extraction