Effects Of DEM Cellsize And Smoothing On Spatially Distributed Slope Length

Distributed erosion slope length is an important topographic factor in soil erosion equation in China,and DEM resolution is an important factor affecting its extraction accuracy.To understand and understand the law of slope length changing with resolution is conducive to soil erosion evaluation and restoration of low-resolution downhill length.In this study,four sub-regions of loess hilly gully terrain were selected,namely ansai,Suide,Tianshui,and Huining,as the research areas.On the basis of 1:10000 digital topographic map data,using ANUDEM has allowed professional interpolation software to generate different hydrological correct DEM resolution,DEM resolution can be divided into discrete terrain and topography smooth two components,the total effect and composition analysis of resolution for the influence of slope,and using the method of histogram matching partition on river basin scale and regional scale to fix the low resolution of slope length,the main conclusions are as follows:(1)the resolution reduce directly lead to the loss of terrain information,the influence of different degrees of terrain information loss for slope degree is different,the effects on slope length deeper slope information entropy,in the actual process of DEM resolution is lower,the variation trend of slope is larger,so in the actual process,the slope is the main factors influencing the slope length cutting.By subtracting topographic features of different resolutions into the multidimensional formula,it is found that the fitting effect is good before the 50m resolution,but error occurs after the 50m resolution,and the growth trend slows down or even shrinks.(2)The total resolution effect makes the slope length expand first and then shrink.In the 0-100m resolution range,the slope length and resolution show a logarithmic growth trend,while in the 100-200m resolution range,the slope length and resolution show a linear decrease trend.At the same time,in the process of expansion,not all the slope length will expand,very long slope length will shrink phenomenon.By analyzing the resolution components,it can be seen that,in terms of numerical statistics,the terrain dispersion is the main factor affecting the slope length expansion,and the semi-variation function analysis of slope length data with different resolutions reveals that,in terms of spatial pattern,the terrain smoothness is the main factor affecting the slope length variation.With the decrease of the resolution,the influence of the smoothing effect shows an increasing trend,while that of the discrete effect gradually decreases.(3)As a cumulative topographic factor,slope length is not only affected by topographic accuracy,but also affected by DEM grid size.Errors in the multidimensional composite formula under low and medium resolution are considered to be that after 50m resolution,the actual extracted slope length is affected by DEM grid size.(4)the slope length of river basin scale division,is between sub basin terrain slope length variation degree is low,and higher negative terrain variation degree of secondary basin,respectively to the distinction between the two parts after repair,repair the results show that the slope length accuracy in numerical statistics and cumulative frequency all has improved,the basin scale of soil erosion assessment found that after repair the amount of soil erosion and erosion classification by repair,but there are still some differences.It was found that due to the small scale of the basic data of the regional scale,a large range of extremely low slope areas appeared in the slope area under the ground resolution,which made it impossible to repair the range during the slope restoration.At the same time,the high resolution slope length range is too large to repair the very long slope length.In terms of mathematical statistics,the regional scale restoration has some errors,and the cumulative frequency is not as good as that of the regional scale.In the evaluation of soil erosion,the remediation topographic factors were superior to the low-resolution topographic factors in the total amount and classification statistics of soil erosion.Figure.29,tab.25,Ref.79...