I'm not sure what you mean by "do something when it's on the ground." You may know this but you do the calibration by first either being told to do it via DJI GO 4 or by finding the place in the GO 4 app that leads you through the calibration process. I calibrate my
P4P indoors well away from magnetic interference. I would do it outside away from interference, but I live in South Dakota and it is very, very cold and because of snow, I can't easily stand anywhere but my driveway.
Incidentally, I brick or paving stone patio shouldn't pose a problem as there is likely no metal in the structure.