Formatting does very little to remove anything from a card.
I have recovered Gb's worth of photos and videos from 2nd hand cards that people have formatted.
If you want to wipe a card and include it with the drone can I suggest formatting in a computer then running something like "H2testw" on the card.
The latter is actually a card capacity (amongst possibly other things) checking program, it does this by writing files to all the nominally available/empty space on the card thereby over writing what ever was there in the first place.
It then reads the files back and checks them somehow against what was written, thereby checking the card.
It can be stopped once the write has completed, another format or simple deletion then 'gets rid' of the test files.
In case anyone is wondering, I was not seeking to recover files but checking the card with a recovery program "Zarx" which outputs a map of any bad sectors encountered during its scan.
If I run Zarx before H2testw I frequently find loads of supposedly deleted photos etc. but if Zarx is run after H2testw Zarx finds nothing 'useful'