Estimation of chlorophyll content for urban trees from UAV hyperspectral images

Shanshan Wei, Tiangang Yin (Corresponding Author), Bo Yuan, Genevieve Lai Fern Ow , Mohamed Lokman Mohd. Yusof, Jean Philippe Gastellu-Etchegorry, Andrew Whittle

Research output: Journal article publicationJournal articleAcademic researchpeer-review


Urban trees provide important ecosystem services to improve cities’ liveability and sustainability. Leaf chlorophyll content (Cab) estimation by remote sensing can help monitor tree health efficiently. However, the Cab retrieval of urban trees is challenging because of the complex canopy structures, backgrounds, and illuminations conditions. This paper proposed an automatic method for partitioning sunlit/shaded pixels and removal of bright-specular/dark-hole and background pixels. In addition, we proposed a new index, the Urban Tree Chlorophyll Index (UTCI), defined as UTCI=(ρ_709-ρ_697)/(ρ_709-ρ_686), based on the simulated hyperspectral images of urban tree using radiative transfer model. This proposed UTCI index outperforms existing narrow-band indices (NBIs) for estimating Cab for complex canopy structures, backgrounds, and illumination conditions evaluated using simulated hyperspectral images. The advantage of the UTCI was also demonstrated when applied to UAV hyperspectral images validated with direct field foliar measurements of Cab. It surpasses existing NBIs, demonstrating a moderate correlation (R2 = 0.34) with Cab under varying irradiance and a strong correlation (R2 = 0.62) with Cab under stable diffuse illumination. This study, for the first time, extensively investigated NBIs for Cab estimation of urban trees from UAV hyperspectral images, providing a theoretical and operational basis for future monitoring of Cab in the management of urban trees. This new method can be potentially applied to other vegetation types with complex canopy structures, backgrounds, and illuminations conditions.
Original languageEnglish
Article number103617
Pages (from-to)103617
JournalInternational Journal of Applied Earth Observation and Geoinformation
Publication statusPublished - 1 Feb 2024


  • Chlorophyll content
  • Hyperspectral remote sensing
  • Narrow-band indices
  • Radiative transfer model
  • Unmanned aerial vehicles (UAV)
  • Urban tree health

ASJC Scopus subject areas

  • Global and Planetary Change
  • Earth-Surface Processes
  • Computers in Earth Sciences
  • Management, Monitoring, Policy and Law


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