During a recent big job under varying lighting conditions I spent a lot of time adjusting shutter speeds, aperture and ISO to avoid motion blur, having to do mental calculations whilst walking over rocky, rough ground and keeping my eye on the drone.
So I’ve grabbed an envelope, turned it over and found that for a given GSD the general equation is shutter speed needs to be close to, or shorter than
speed in m/s * 100 /GSD.
speed in km/hr * 28/GSD
speed in mph * 45/GSD
For example @ 40km/hr with a GSD of 2cm, you’d want faster than 1/500.
Yes the calculation says 1/560, but a ~10% blur isn’t noticeable. 1/250 could cause problems though.