The fraction of vegetation cover (FVC) is often estimated by unmixing a linear mixture model (LMM) to assess the horizontal spread of vegetation within a pixel based on a remotely sensed reflectance spectrum. The LMM-based algorithm produces results that can vary to a certain degree. depending on the model assumptions. For example. https://www.roneverhart.com/Jouer-Soft-Focus-Hydrate-Set-Powder/