To a maximum depth, how deep should ground letters or signals be?

The correct depth for ground letters or signals is 6 inches. This depth is typically recommended because it balances visibility and durability. Markings positioned at this depth are generally less susceptible to damage from environmental factors such as rain, wind, and foot traffic, while still being visible enough for aerial or distance observation in a search and rescue scenario.

Choosing a shallower depth, like 4 inches, may lead to the markings being easily disturbed or obscured by elements such as soil shifting or vegetation growth. Conversely, going deeper, such as 8 or 10 inches, risks making the signals less visible and harder to identify, which can be counterproductive during critical search and rescue operations where quick recognition and effective communication of locations are essential.