 The fraction of Absorbed Photosynthetically Active Radiation, FAPAR, is an important plant physiological index used for assessing vegetation's ability to absorb PAR, sequester carbon in the atmosphere, monitor plant health and productivity, and food security assessment. Multispectral and Hyperspectral Unmanned Aerial Vehicle, UAV, imaging systems can provide precise estimation of FAPAR using chemometrics, but data pre-processing procedures are cumbersome, making large-scale mapping challenging. This study applied image-processing protocols and a chemometric model to a lightweight, frame-based, and narrow-band, 10 nanometers, UAV imaging system to estimate FAPAR over a relatively large cultivated land area with various low-stature vegetation of tropical crops along with native and non-native grasses. The results indicate that 77% of the FAPAR variation was explained by the model, an all-band sensitive to foliar pigment concentrations, canopy structure, and all leaf water content may contribute to the estimation, especially those located close to or within the near-infrared spectral region. This study demonstrates that this narrow-band frame-based UAV system would be useful for vegetation monitoring, and with proper pre-flight planning and hard-way improvement, the mapping of a narrow-band multispectral UAV system could be comparable to that of a manned aircraft system. This article was authored by Choe Ying Huang, Hinlin Wei, Zhengyou Rau, and others.