Thanks for the response, @muzammil360. I am trying to ortho-rectify images based on the latitude/longitude/altitude and roll/pitch/yaw metadata provided in the image EXIF. I am trying to compute a 3x3 rotation matrix that rotates from a East/North/Up coordinate system into image coordinates.
The roll/pitch/yaw coordinate convention seems to differ from other drones (like DJI) which I already know how to interpret. It appears that the roll/pitch/yaw convention is very similar to DJI, but pitch=0 is nadir (whereas DJI defines pitch=-90) as nadir.
Once I compute a rotation matrix I will then project the image to a ground plane in world coordinates.