Abstract: The topography of the Hengduan Mountains is complex. When vertical projection area is used to represent landscape surface area for quantitative calculations, large errors will occur. Taking Yajiang county in the middle of the Hengduan Mountains as an example, the landscape surface area of each land use type in Yajiang county is calculated by the geological significance of the surface roughness based on DEM data and surface cover product data sets. And the difference between landscape surface area and vertical projection area is analyzed. The results show that the differences between surface area and projected area in Yajiang county positively correlate with the DEM resolution, and negatively correlate with altitude. The main factor affecting the differences between the surface area and the projected area is the slope. As the slope increases, the differences and the growth rate of the differences also increase. The differences between surface area and projected area are diverse because of the different land use types.

Key words: landscape surface area, vertical projection area, surface roughness, the Hengduan Mountains, Yajiang county