Filtering airborne LiDAR point clouds based on a scale-irrelevant and terrain-adaptive approach

Separating ground from non-ground points is a challenging and essential task before the applications of airborne Light Detection And Ranging (LiDAR) data. The classical filters generally show good results on simple landscapes, but suffer from large filtering errors on complex landscapes with steep slopes and terrain discontinuities. To produce more satisfactory results over these landscapes, a scale-irrelevant and terrain-adaptive interpolation-based filter is presented in this paper. The contributions of the proposed method include a 1D spline-based algorithm for the collection of evenly distributed ground seeds as many as possible, a scale-irrelevant interpolation for estimating the heights of unclassified points and a terrain-adaptive elevation threshold to adapt to various terrain characteristics. The performance of the proposed method was first evaluated on the International Society Photogrammetry and Remote Sensing (ISPRS) benchmark dataset. Results show that the proposed method with the average total error of 2.70% and kappa coefficient of 90.84% outperforms the existing filtering algorithms developed in recent decade (2010-2020). The performance of the proposed method was further assessed on four high-density airborne LiDAR point clouds located in urban and forested sites and compared with four state-of-the-art filters including progressive morphological filter (PMF), cloth simulation filter (CSF), progressive TIN densification (PTD) and multiresolution hierarchical filter (MHF). Results demonstrate that the proposed method is averagely more accurate than the well-known filters in terms of total error and kappa coefficient, and much faster than PTD and MHF. Moreover, the proposed method produces more satisfactory DEMs than the classical methods.