You can't underestimate the efficiency of caltorps. When they lie in the grass you do not recognize them. And if you are a late medieval infantry, equipped with helmet and visor, through which you see even less, and have to rush the enemy, you have absolutely no chance. In this respect, scanning the battlefield would make absolute sense, provided there is a chance to do so before the battle.

Especially in view of the large quantities in which these caltrops were purchased and stocked. In 1642, the city of Hamburg alone had over 23,959 pieces, and at the Coburg fortress there are still large chests full of them today.

However, from the late Middle Ages, I am so far only aware of the mentions in the Bellifortis and war technical manuscripts, but no factual reports of scanning and cleaning them from the battle fields.