DEM地面形态重构方法的精度差异特征研究

Accuracy Differences among Approaches of DEM Surface Morphology Reconstruction

依据DEM地形建模过程,阐述了DEM地面形态重构概念,并以黄土丘陵1∶5万DEM数据为例,采用高程数值误差场和局地坡面形态误差场相结合的分析技术,实验分析了双线性、三次卷积、局部二次多项式、规则样条函数等常用插值方法在基于加密格网的DEM地面形态重构过程中的精度差异,以及DEM地面形态可重构的基本条件等问题。研究表明:在高程数值误差的极值大小、离散程度、空间分布等方面,规则样条函数插值法具有最好的地面形态重构精度,其次为局部二次多项式、三次卷积和双线性插值法;对于已确定综合尺度的地形,存在满足高保真地面形态描述要求的最佳DEM格网分辨率阈值,只有当实际DEM格网分辨率等于或高于该阈值时,才有可能无歧义、高精度地重构出DEM所描述的综合地形的地面形态。

According to the process of DEM terrain modeling,the concept of DEM surface morphology reconstruction is stated firstly.Then taking 1∶ 50 000 DEM in the loess hilly region as test data,this paper analyzes the basic conditions of DEM surface morphology reconstruction,and the accuracy differences of interpolation approaches in the process of density-grid based reconstruction.The interpolation approaches include bilinearity,cubic convolution,local quadratic polynomial,and regularized spline function.In the experimental process,the analysis method,combined the error fields of elevation values and local slope shapes,is applied.The testing results show the following conclusions：1） In aspects of the extreme value,the discrete degree and the spatial distribution of elevation numerical error,regularized spline function is the optimal interpolation method to reconstruct surface morphology,followed by local quadratic polynomial,cubic convolution and bilinear interpolation.2） For the terrain with a defined comprehensive scale,an optimal threshold of DEM resolution is existed to meet the demand of DEM surface morphology reconstruction with high fidelity slope shapes,and the reconstructed DEM can reach the best accuracy in the comprehensive scale when the reconstruction resolution is equal to or greater than the above threshold.