What are "sand" and "water" in Feng Shui?

Sand refers to the heights of peaks, hills, piers, trees and buildings around cave sites. In a narrow sense, water refers to rivers, lakes, oceans, ponds, fish ponds, ponds, reservoirs, gullies, glaciers, waterfalls and springs. Whether in motion or at rest, it is obvious. Broadly speaking, in addition to the water above, it also includes low-lying places, roads and so on. At the same time, Feng Shui believes that an inch high is sand and an inch low is water. Teacher Xuan Yi said that this is a way to judge "sand" and "water" when the characteristics are not obvious.