Since the autopilot system collects the angle data, which indicates that the image rotates around its symmetry center but the world file adopts the upper-left as its rotation center, we have to change the center rotation to the upper-left rotation and reduce the error caused by rotation.
The remote sensing images collected based on the unmanned aerial vehicle rotate around their symmetry center theoretically, but the images georeferenced based on the world file rotate around their upper-left corner.
In Figure 4, when the image rotates around its upper-left corner and the image rotates around its symmetry center according to the same angle, the correspondent edges of images after rotation are parallel to each other.
[theta] is the rotation angle of the image rotating around the symmetry center. w is the width of the raw image, and h is the height of the image.
In formula (9), [DELTA]x and [DELTA]y are, respectively, the translation amounts on the x and y directions which indicate the position deviation that the image rotates around its symmetry center relative to the image rotating around the upperleft corner.