Benchmarking Deep Learning Architectures for Urban Vegetation Point Cloud Semantic Segmentation From MLS

Vegetation is crucial for sustainable and resilient cities providing various ecosystem services and well-being of humans. However, vegetation is under critical stress with rapid urbanization and expanding infrastructure footprints. Consequently, mapping of this vegetation is essential in the urban environment. Recently, deep learning (DL) for point cloud semantic segmentation has shown significant progress. Advanced models attempt to obtain state-of-the-art performance on benchmark datasets, comprising multiple classes and representing real-world scenarios. However, class-specific segmentation with respect to vegetation points has not been explored. Therefore, selection of a DL model for vegetation points segmentation is ambiguous. To address this problem, we provide a comprehensive assessment of point-based DL models for semantic segmentation of vegetation class. We have selected seven representative-point-based models, namely, PointCNN, KPConv (omni-supervised), RandLANet, SCFNet, PointNeXt, SPoTr, and PointMetaBase. These models are investigated on three different datasets, specifically Chandigarh, Toronto3D, and Kerala, which are characterized by diverse nature of vegetation and varying scene complexity combined with changing per-point features and classwise composition. PointMetaBase and KPConv (omni-supervised) achieve the highest mIoU on the Chandigarh (95.24%) and Toronto3D datasets (91.26%), respectively while PointCNN provides the highest mIoU on the Kerala dataset (85.68%). The article develops a deeper insight, hitherto not reported, into the working of these models for vegetation segmentation and outlines the ingredients that should be included in a model specifically for vegetation segmentation. This article is a step toward the development of a novel architecture for vegetation points segmentation.