Fig. 9. The derivative chlorophyll index (DCI) applied to hyperspectral derivative reflectance collected with the compact airborne spectrographic imager (CASI) airborne sensor. Remote sensing images were collected over the two study sites with low (top image) and high (bottom image) stress conditions to map the double peak as an indicator of stress. Images show the 500- x 500-m sugar maple areas with the 20- x 20-m study sites with highest field-measured C_a+b and F_v/F_m (GY41, F_v/F_m = 0.81, C_a+b = 38.8 µg/cm², top image) and lowest F_v/F_m (MD35, F_v/F_m = 0.75, C_a+b = 19.08 µg/cm², bottom image). Areas of vegetation stress are identified on the 2- x 2-m spatial resolution airborne images in red.