As mentioned in my 10/25/2018 blog, “Flying in High Winds – What Could Possibly Go Wrong?,” wind can affect your drone’s flight control system. In severe situations, its effects are immediately apparent on your screen, such as an image that bounces around. However, there’s another more subtle effect that can impact the quality of your videography, which you should know about.
Review of Your Drone’s Flight Control System
First, let’s review what keeps your drone stable while in flight. Today’s sophisticated drones use a magnetic compass and the global positioning system (GPS) to determine the drone’s heading and position. The drone’s inertial navigation system is always comparing its solution with that of GPS to hold the drone in position and to keep the camera steady. So, even if the wind is buffeting your drone, its control system is doing a pretty good job of holding the camera steady.
However, if the wind is high enough and the gusts strong enough, the drone’s flight control system can be driven into its non-linear region. This appears as bouncing around in the video feed to your screen and recorded images if you’re shooting video. Your only solution is to wait until the wind settles down and try again.
Wind Can Affect Your Videography in Other Ways
While flying your drone manually, you’ll probably never notice the effect of a crosswind. However, in programmed flights, such as DJI’s waypoint mode, you may notice a yawing (heading) offset while the drone is flying from point A to point B. This offset is known as “crabbing.”
Crabbing is where the yaw axis of the camera offsets from the drone’s direction of travel. Stated another way, while your drone’s course toward Point B may be on a direct heading, it offsets in yaw to another angle, typically turning into the wind.
In light winds, the crabbing effect is minor, but as the crosswind speed picks up it becomes more pronounced. Its effect on your video? You’ll notice your drone’s video image offset a few degrees from the straight-ahead direction.
What Causes Crabbing?
Your drone does a pretty good job of maintaining its heading and position along the desired track over ground. However, it still has to adjust heading to compensate for wind and stay on the objective track. When your drone adjusts the heading, its camera crabs over to an offset angle. This is simply vector math and is commonly encountered in aviation scenarios (as well as for boats in crosscurrents, etc.). Think of an airplane landing in a crosswind – notice how its angle relative to the runway is offset? That’s crabbing.
What Can I Do With This Information?
With awareness of crabbing, you can look for its effect on your videography. If it becomes objectionable then you can increase your drone’s speed (again, vector math), wait for a calmer day, or crop out some of the offset in postprocessing.