The word "地上" is formed by directly combining two conceptual characters: "地", which represents the concept of "ground" or "earth", and "上", which represents the concept of "above" or "on top of". Their combination creates a new, compound spatial concept where the meaning of the second character ("上") is applied to the domain of the first ("地"), resulting in the integrated idea of "the surface of the ground" or "the area on the earth".