数字地形分析中适宜分析窗口选择方法的评价

Analysis on the Approach to Determine an Appropriate Window Size for Grid-Based Digital Terrain

基于栅格DEM(digital elevation model)计算局域地形属性时,所采用的分析窗口将直接影响数字地形分析结果,因此在实际应用中应选择适宜分析窗口。由于地形条件是随空间变化的,因此随空间变化的适宜分析窗口应比通常所用的全局固定的3×3窗口更为合理。目前通过定量计算获得随空间变化适宜分析窗口的方法是多窗口局部地表形态刻画法。选用3个具有不同地形特征的研究区,在不同分辨率下分别将坡度、剖面曲率用于该方法来确定适宜分析窗口,对实验结果进行分析评价。结果表明,当利用不同地形信息时,所得的适宜分析窗口情况明显不同。进一步的实验分析发现,与传统所用的全局固定3×3窗口相比,该方法所识别出的随空间变化的适宜分析窗口结果对于实际应用结果没有明显差别。因此该方法有效性存疑,尚不能作为确定适宜分析窗口的有效方法,还需进一步开展方法研究,以设计出合理有效的方法来识别随空间变化的适宜分析窗口。

Due to the scalar effects of changing window sizes in grid-based digital terrain analysis,it is important to determine an appropriate window size for calculating local topographic attributes in practice.A reasonable appropriate window size must be spatial-variant but constant,such as the often-used window size of 3 × 3.Currently,a potentially-available approach for determining an appropriate window size characterizes a scaleeffect curve derived from a specific kind of local topographical attribute calculated for different window sizes,as proposed by Schmidt and Andrew （2005）.However,there has ben little evaluation of this approach,such as research on the effects of different topographic attributes used,applicability in areas with different terrain conditions under different grid sizes.In this paper we conduct an experiment to evaluate this approach.We test two kinds of local topographic attributes （i.e.,slope gradient and profile curvature） in three study areas with different terrain conditions under different grid sizes.Experimental results show that the results for appropriate window size achieved based on different topographical attributes were totally different.However,further analysis shows that slope calculation in real applications,the results of spatially-variant appropriate window size by the tested approach perform almost same as the constant window size of 3 × 3,which is the traditional option.So the current approach to determining spatially-variant appropriate window size might not be effective.Further study on a design for a new and effective approach is needed to determine the spatially-variant appropriate window size for calculating local topographic attributes