Journal Article

Tree-CRowNN: A Network for Estimating Forest Stand Density from VHR Aerial Imagery

Zhang, Ying, Richardson, Galen, Richardson, Elisha, Lovitt, Julie

2023

Overview

Estimating the number of trees within a forest stand, i.e., the forest stand density (FSD), is challenging at large scales. Recently, researchers have turned to a combination of remote sensing and machine learning techniques to derive these estimates. However, in most cases, the developed models rely heavily upon additional data such as LiDAR-based elevations or multispectral information and are mostly applied to managed environments rather than natural/mixed forests. Furthermore, they often require the time-consuming manual digitization or masking of target features, or an annotation using a bounding box rather than a simple point annotation. Here, we introduce the Tree Convolutional Row Neural Network (Tree-CRowNN), an alternative model for tree counting inspired by Multiple-Column Neural Network architecture to estimate the FSD over 12.8 m × 12.8 m plots from high-resolution RGB aerial imagery. Our model predicts the FSD with very high accuracy (MAE: ±2.1 stems/12.8 m2, RMSE: 3.0) over a range of forest conditions and shows promise in linking to Sentinel-2 imagery for broad-scale mapping (R2: 0.43, RMSE: 3.9 stems/12.8 m2). We believe that the satellite imagery linkage will be strengthened with future efforts, and transfer learning will enable the Tree-CRowNN model to predict the FSD accurately in other ecozones.

• Publisher: MDPI AG
• Subject: Aerial photography / Annotations / Artificial intelligence / Automation / Canada / Comparative analysis / convolutional neural network / Datasets / Deep learning / Density / Distribution / ecological zones / Floods / forest stand density / forest stands / Forests / Forests and forestry / high-resolution imagery / Identification and classification / Image resolution / Lidar / Machine learning / Mapping / Measurement / Mixed forests / Neural networks / Photography, Aerial / Remote sensing / Satellite imagery / Satellites / Sentinel-2 / stand density / Stems / Target masking / Transfer learning / Trees / Vegetation