基于DEM分形特征的坡度尺度变换模型

利用DEM提取坡度具有明显的尺度依赖性,探求DEM在不同尺度下表现出的规律关系,建立多尺度变换模型,以实现不同尺度间的转换是地形分析研究的热点和难点。本文阐释了DEM表面与地表粗糙度分形维数值的地学意义及内在关系,并利用分形对象的自相似性原理,建立了一种基于DEM分形特征的坡度尺度变换模型。选取四川丘陵地区某小流域为研究区,进行坡度尺度变换实验和误差分析,结果表明该模型能有效实现坡度尺度变换:在非平坦地区(坡度>1°)一般重采样方法变换得到的坡度误差为该方法的1.86倍;从信息熵理论分析,经该方法转换后的坡度信息得到了显著恢复。对于无1︰1万及以上精度地形数据的西南山区,利用该方法获取高精度坡度数据具有重要的理论价值和现实意义。     

Spatial Scale Problems and Geostatistical Solutions: A Review

The concept of spatial scale is fundamental to geography, as are the problems of integrating data obtained at different scales. The availability of GIS has provided an appropriate environment to re-scale data prior to subsequent integration, but few tools with which to implement the re-scaling. This sparsity of appropriate tools arises primarily because the nature of the spatial variation of interest is often poorly understood and, specifically, the patterns of spatial dependence and error are unknown. Spatial dependence can be represented and modelled using geostatistical approaches providing a basis for the subsequent re-scaling of spatial data (e.g., via spatial interpolation). Geostatistical techniques can also be used to model the effects of re-scaling data through the geostatistical operation of regularization. Regularization provides a means by which to re-scale the statistics and functions that describe the data rather than the data themselves. These topics are reviewed in this paper and the importance of the spatial scale problems that remain is emphasized.