Fig. 2
From: Quantifying cereal crop movement through hemispherical video analysis of agricultural plots
Rotation of field coordinates. The camera orientation is determined from still frames (a). The sample still frame shows the position of the inner (orange dashed rectangles) and outer (blue dashed rectangles) replicates in view with respect to the camera track (a). The red square on the panel is masked out from the rest of the image, and the leftmost corner is identified with the color values ± 40 pixels from this corner used to determine which way the panel is facing (b). Once the direction and degree in this direction that the image is rotated is quantified (Θoff), the field design coordinates are rotated in that direction such as 45.9° toward the Northeast (c) or 41.9° toward the southwest (d)