*2.5. Vegetation Indices*

On hyperspectral images of ground canopy data, 20 VIs were tested to visualize crop heterogeneity and to detect yellow rust in the field. The composition was used because it has previously been successfully tested as an indicator for crop vitality [37]. The composition of VIs was chosen according to Behmann et al. [37]. Due to the limitation of available bands of the Rikola camera, only 16 VIs were used for UAV data and the ARVI, mRESR, mRENDVI, and SIPI were excluded.
