Method of modifying existing DEM by adding a small value can produce more realistic drainage pattern rather than parallel flow over flat surface.
在地势平坦地区，采取在原DEM上加微小修正值的办法，可以得到理想的模拟结果。
2
This experiment bases on different permeability in different directions of coal seam cleats. To arrange methane drainage direction the directions vertical and parallel to face cleat are adopted.