基于地表粗糙度地学意义的地表真实面积计算

地表真实面积很难直接测量和计算,一般利用投影面积代替地表面积。在地形起伏较小的平原地区,地表真实面积和投影面积相差不大,但在地形起伏复杂的山区,两者差异较为明显,为计算地形起伏复杂的横断山区地表面积,选取西藏自治区昌都县作为研究区,推导了地表粗糙度的地学意义,基于地表粗糙度地学意义计算地表真实面积并定量分析了地表真实面积与垂直投影面积之间的差异。实验结果表明:相同土地覆被下,DEM分辨率越高,地表真实面积与垂直面积差异越大;草地、灌木林地、有林地、疏林地和难利用地的地表真实面积与其垂直投影面积差异较大,分别占垂直投影面积的11.275%、13.447%、16.586%、13.644%和17.282%,对于地形起伏复杂的山区而言,地表真实面积与垂直投影面积之间的差异不容忽视;坡度越大,地表真实面积与垂直投影面积之间的差异越明显,当坡度>75°时,差异迅速增大。基于地表粗糙度地学意义可快速获取地表真实面积,若建立典型地区地表粗糙度数据库,可为该地区土地利用变化、森林资源调查和作物面积估产等提供更加科学有效的数据。

Calculating Landscape Surface Area based on the Geology Significance of the Surface Roughness

It’s difficult to directly measure or calculate the surface area.The surface area is often replaced by projected area.In the plain area,the differences between these two kinds of area are not worth being noticed,but in the mountainous area,the differences are obvious.In order to calculate the surface area of Hengduan mountainous area which has the dramatic mountain terrain ,Qamdo County in Tibet was chose as the study area.The geology significance of the surface roughness is worked out,and based on that the surface area has been calculated.The differences between the surface area and projected area have been quantitatively analyzed.The results showed that compared with the same land use,the differences of the higher the solution of DEM data is the more obvious between the surface area and projected area.The differences of the two kinds of area for grassland,shrub land,forest land,open forest land and wasteland were obviously,which were accounted for 11.275%,13.447%,16.586%,13.644% and 17.282% of their projected area.The differences between the surface area and projected area in the dramatic mountain terrain can’t be ignored.The differences of the two kinds of area increased with the increasing of slope,especially when the slope is more than 75 degree.Based on the geology significance of the surface roughness,the landscape surface area which can offer more scientific and effective data for land use change detection,forest resources investigation,crop production estimation with establishing the surface roughness database in typical area can be quickly access to.