Haha,
To be fair - the British Army does do training "similar" to this, troops advance up a hill side - there are markers staked out up the same. A gunner (GPMG usually) essentially leads the advancing troops such that they're always advancing with rounds impacting in front and cracking above.
Safety comes in the form of dial sights on the gimpy and the markers being at known elevations on said dial site and the directing staff are paying attention to what's going on.
It does however get the juices flowing if you're one of said troops.
for ref - M2 with C2 sight:
