Research on Effects of DEM Spatial Scale Based on Different Terrain Type and DEM Resolution

In order to examine the relationship between the terrain-discretization and terrain-smothing effects on topographic characteristics computation and the terrain type and DEM resolution,DEM for 57 locations containing 500 rows × 500 columns and DEM for 1 location composing of 1500 rows × 1500 columns derived from SRTM3 data are used.By comparing the topographic characteristics computed from the original 100m,1000m and new 100m DEM,it can be concluded that the effects of DEM resolution on slope and topographic index mainly result from terrain smoothing,and the terrain discretization accounts for most of the difference between upslope contributing area per unit contour values calculated from 100m and 1000m DEM.The terrain discretization and smoothing are influenced by terrain type.Both of them are related to the terrain variation and scale feature.As the DEM resolution increases,the discretization effect on slope and the smoothing effects on upslope contributing area and topographic index will become gentle,and other will keep on augmenting.These three conclusions can be regarded as the theoretic basis for solving the hydrologic scale issue.