不同分辨率DEM提取切沟形态特征参数的转化研究

选取黄土丘陵区岔巴沟流域不同位置和不同沟道级别的30条典型切沟为研究对象,基于三维激光扫描技术(LIDAR),建立了基于高分辨率DEM提取切沟形态特征的方法,对比分析了0.1m与5m2种分辨率DEM提取切沟形态特征参数的差异,实现对低分辨率DEM提取的切沟形态特征参数向高分辨率尺度转化。结果表明:基于三维激光扫描技术获取的0.1m高分辨率DEM提取的切沟形态特征值与手工测量的切沟形态特征值之间无显著差异,三维激光扫描技术提取的切沟长度、宽度、深度、表面积和体积分别是手工测量的94.0%,109.1%,107.7%,80.1%和109.0%,表明三维激光扫描技术获取的0.1m高分辨率DEM可较准确地描述切沟形态特征。0.1,5m2种分辨率DEM提取的切沟长度间无显著差异,但2种分辨率DEM提取切沟宽度、深度、表面积和体积间差异显著。5m分辨率DEM提取的切沟宽度、表面积和体积分别较实际值分别偏大28.6%,25.6%和19.7%;而其提取的切沟深度较实际值偏小37.0%。据此,通过模型筛选,分别建立了0.1m高分辨率DEM与5m分辨率DEM提取的切沟宽度、表面积和体积转换模型。模型验证结果表明,本研究所构建的切沟宽度、表面积和体积转换模型的决定系数均大于0.6,模型有效性系数均大于0.5,说明3个转换模型均具有较好的预报精度,为研究黄土丘陵区沟蚀特征提供了重要方法和手段。

Transformation of Gully Morphological Characteristic Indicators Extracted from DEMs of Different Resolution

Gully morphological characteristic indicators are important parameters to study gully erosion processes quantitatively, but there are only a few reports on the study of gully morphological characteristics at active stage due to the limitation of DEM resolution. 30 typical gullies were randomly selected in different watershed locations and gully orders. Extraction method of gully morphological characteristic indicators was established based on the 3-D laser scanning technique (LIDAR), differences of gully morphological characteristic indicators extracted from 0.1 m and 5 m DEMs were analyzed and transform models of gully morphological characteristic indicators between different resolution DEMs were established. The results showed that gully morphological characteristic indicators extracted from 0.1 m-resolution DEM and manual measurement had no significant difference; gully length, width, depth, surface area and volume extracted from 0.1 m resolution DEM was 94.0%, 109.1%, 107.7%, 80.1% and 109.0% of that obtained by manual measurement, indicating that 0.1 m-resolution DEM could be used to extract gully morphological characteristic indicators accurately. Gully length extracted from 0.1 m-resolution DEM had no significant difference with that extracted from 5 m-resolution DEM, while gully width, depth, surface area and volume extracted from 0.1 m-resolution DEM had significant difference with those extracted from 5 m-resolution DEM. Gully width, surface area and volume extracted from 5 m-resolution DEM was 28.6%,25.6% and 19.7% greater than that extracted from 0.1 m-resolution DEM, respectively, while gully depth extracted from 5 m-resolution DEM was 37% smaller than that extracted from 0.1 m-resolution DEM. Therefore, transform models of gully width, surface area and volume were established. Model validation results showed that the correlation coefficients of gully width, surface area and volume transform model were all greater than 0.6 and effectiveness coefficients were all greater than 0.5, indicating that the accuracies of the three transform models were all acceptable. This study provides an important method for the study of gully erosion characteristics in the loess hilly-gully region.