Figure 1. By knowing the position of the sun, the position of the plot and the position and orientation of the camera when an image is triggered (IMAGE)
Caption
(a)different geometric relations can be calculated.The position directly below the drone is in nadir orientation. The vertical angle at which drone and sun are seen from the observed plot are the elevations of drone and sun respectively. The azimuth of the sun is the clockwise horizontal angle at which the sun is seen from the observed plot from north (b)The position of the plot can be described as planar distance between drone and plot in direction of the sun (b) or in sowing row direction (c) Another option to describe the positon of the plot relative to the drone is by viewing angles as is shown for angles relative to sun direction (d)but not shown for the sowing row direction. Elements in the principal optical planes in drone or sun direction are in bright blue, cardinal direction in dark blue. The dimensions of interest and related covariates are in orange. Small black angle marks and short parallel black lines indicate perpendicularity and parallelism respectively.
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