用无人机影像与激光雷达数据,实现自动森林树群划分,准确率达90%以上。
Assessing airborne laser scanning and aerial photogrammetry for deep learning-based stand delineation
- 基于U-Net模型,融合多光谱影像与不同来源的冠层高程图进行语义分割。
- 三种数据组合精度均达0.90~0.91,差异不显著,表明结果稳定可靠。
- 适合林业自动化管理,尤其适用于需快速处理大规模遥感数据的场景。
精准的森林树群边界划分对森林调查与管理至关重要,但目前仍主要依赖人工且主观性强。已有研究显示,结合航空影像与机载激光扫描(ALS)数据,深度学习可生成与专家判读相当的树群划分结果。然而,数据源间的时间错位限制了其实际应用。利用数字摄影测量法(DAP)生成的冠层高程模型(CHMs)具有更好的时间一致性,但可能平滑冠层表面与林窗,引发其能否替代ALS-derived CHMs的疑问。同样,有研究建议引入数字地形模型(DTM)以提升划分性能,但尚未在文献中得到验证。本研究以专家划定的树群为参考,采用基于U-Net的语义分割框架,在挪威东南部六个市政区进行跨区域验证,比较了三种组合:(i) 多光谱影像+ALS-derived CHM,(ii) 多光谱影像+DAP-derived CHM,(iii) 多光谱影像+DAP-derived CHM+DTM。结果显示,三组数据的总体准确率均在0.90至0.91之间,表现相近。模型预测结果间的吻合度远高于与参考数据的吻合度,凸显模型的一致性及人工划分的主观性。尽管DAP-CHMs结构细节减少,但表现相似;加入DTM也未带来性能提升,说明该框架对输入数据变化具有鲁棒性。研究结果表明,可通过整合具有时间一致性的ALS数据与DAP点云项目,构建大规模深度学习训练数据集。
原文摘要 · Abstract (English)
Accurate forest stand delineation is essential for forest inventory and management but remains a largely manual and subjective process. A recent study has shown that deep learning can produce stand delineations comparable to expert interpreters when combining aerial imagery and airborne laser scanning (ALS) data. However, temporal misalignment between data sources limits operational scalability. Canopy height models (CHMs) derived from digital photogrammetry (DAP) offer better temporal alignment but may smoothen canopy surface and canopy gaps, raising the question of whether they can reliably replace ALS-derived CHMs. Similarly, the inclusion of a digital terrain model (DTM) has been suggested to improve delineation performance, but has remained untested in published literature. Using expert-delineated forest stands as reference data, we assessed a U-Net-based semantic segmentation framework with municipality-level cross-validation across six municipalities in southeastern Norway. We compared multispectral aerial imagery combined with (i) an ALS-derived CHM, (ii) a DAP-derived CHM, and (iii) a DAP-derived CHM in combination with a DTM. Results showed comparable performance across all data combinations, reaching overall accuracy values between 0.90-0.91. Agreement between model predictions was substantially larger than agreement with the reference data, highlighting both model consistency and the inherent subjectivity of stand delineation. The similar performance of DAP-CHMs, despite the reduced structural detail, and the lack of improvements of the DTM indicate that the framework is resilient to variations in input data. These findings indicate that large datasets for deep learning-based stand delineations can be assembled using projects including temporally aligned ALS data and DAP point clouds.
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