Highly Detailed and Generalizable Broadleaf Tree Crown Instance Segmentation from UAV Imagery

TL;DR

This paper introduces a deep learning model for detailed and generalizable tree crown segmentation in broadleaf forests using UAV imagery, trained on extensive annotated datasets, and applicable across diverse forest types.

Contribution

The authors developed a Mask2Former-based deep learning model trained on a large annotated dataset, enabling detailed and generalizable tree crown segmentation from UAV imagery.

Findings

High segmentation accuracy in complex broadleaf forests

Model performs well across different geographic regions

Large annotated dataset is key for generalization

Abstract

We present a highly detailed instance segmentation model for delineating individual tree crowns in natural broadleaf forests using aerial imagery acquired by unmanned aerial vehicles (UAVs). Tree crown delineation in broadleaf forests is more challenging than in other forest types due to diversity of crown shapes and the lack of clearly defined treetops. To address this issue, we developed a deep-learning-based crown segmentation model trained on high-quality annotated crown outlines. We manually delineated 18,507 crown polygons from orthomosaic images collected across seven forests in Japan by skilled annotators, and developed a model based on Mask2Former with multiple backbone architectures. The best model achieved high segmentation performance in structurally complex broadleaf forests using only RGB imagery. This performance was maintained when applied to geographically distinct forests within Japan, as well as to biologically distinct tropical rainforests in Borneo. These results demonstrate that using a large number of high-quality annotated datasets is critical for achieving detailed and generalizable crown segmentation across diverse forest ecosystems. The developed model has been integrated into DF Scanner Pro, a software that supports practical forest monitoring using UAVs, and this implementation is expected to enable a wide range of users to analyze tree-level information in broadleaf forest from UAVs.