Abstract
This study addressed the problems of difficult parameter selection of ground point filtering algorithm, slow speed, and susceptibility to wrong classification points of traditional interpolation algorithm in extracting canopy height model (CHM) from dense point cloud produced by structure-from-motion (SfM). Finding the true ground is vital for canopy height estimation using UAV RGB point cloud, especially for semi-arid area where cloud points of short vegetation like shrubs and dwarf trees generally mixed up with the ground points. This paper proposes a ground point extraction strategy that combines the advantages of structural and spectral filtering. Specifically, spectral filtering simplifies the threshold selection for structural filtering, while structural filtering removes the outliers from spectral filtering. Considering the misclassified points in the ground filtering algorithm, a fast, nonparametric ground point interpolation algorithm was used to suppress the wrong classification points. This novel algorithm is based on the basic idea of least square quadratic fitting and prediction of terrain profile (PF). The quantitative results show that compared to Inverse Distance Weighting (IDW), Radial Basis Function (RBF), and Ordinary Kriging (OK), it takes less time (PF: 122s, IDW: 518s, RBF: 1374s, OK: 1129s), and has lower RMSE (PF: 0.301 m, IDW: 0.549 m, RBF: 0.903m, OK: 0.427m).
Highlights
SEMI-ARID areas cover approximately 15% of the global land area and provide unparalleled economic and ecologically critical services; these areas are among the world's most threatened and fragile ecosystems [1], [2]
Setting a small filtering threshold can reduce the probability of classifying low plants as ground points, but it will filter out a large number of real ground points simultaneously
Regardless of the ground point interpolation algorithm, it is affected by the ground point density
Summary
SEMI-ARID areas cover approximately 15% of the global land area and provide unparalleled economic and ecologically critical services; these areas are among the world's most threatened and fragile ecosystems [1], [2]. As an essential component of semi-arid ecosystems, vegetation is the primary producer of ecosystems, most closely linked to other elements (e.g., soil water and groundwater). It has important implications in terms of. Zhang are with the School of Environment Science and Spatial Informatics, China University of Mining and
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