Daily narrow-angle hemispherical photography for long-term canopy cover phenology observation—A case study of rubber plantations in Xishuangbanna-Supplementary materials

To address this gap, we deployed ground-based camera traps with narrow-view hemispherical images following hemispherical photography protocols to derive canopy cover and chromatic coordinates (GCC, RCC) in a rubber plantation (Xishuangbanna, China) under normal and irrigation management.

Using piecewise linear regression models (PLRMs), we validated these ground-based metrics against coincident UAV photogrammetry. Our results demonstrated high consistency between ground-based and UAV-derived canopy cover during stable periods. Crucially, PLRMs fitted to ground-based data achieved higher accuracy (R² = 0.9785 and 0.9258) than UAV data (R² = 0.8813 and 0.7772), capturing finer dynamics during defoliation and refoliation of rubber trees.