DEM分辨率对黄土侵蚀沟形态特征表达的不确定性分析
李思进(1996— ),男,山东济宁人,博士生,主要从事研究DEM数字地形分析研究。E-mail:lisijin1411@163.com |
收稿日期: 2019-07-03
要求修回日期: 2019-12-05
网络出版日期: 2020-05-18
基金资助
国家自然科学基金项目(41930102)
国家自然科学基金项目(41971333)
江苏高校优势学科建设工程资助项目
版权
Uncertainty of the Morphological Feature Expression of Loess Erosional Gully Affected by DEM Resolution
Received date: 2019-07-03
Request revised date: 2019-12-05
Online published: 2020-05-18
Supported by
National Natural Science Foundation of China(41930102)
National Natural Science Foundation of China(41971333)
Priority Academic Program Development of Jiangsu Higher Education Institutions
Copyright
黄土侵蚀沟的地形表达是开展黄土沟谷侵蚀研究的基础工作,利用数字高程模型(DEM)定量描述侵蚀沟特征有助于研究侵蚀沟的形态变化和发育过程。基于DEM数据计算多种指标对黄土侵蚀沟特征进行描述是目前侵蚀沟研究中最为常用的方法。但是,受到格网DEM数据结构的限制,其计算结果会存在一定的不确定性。在侵蚀沟地形表达时,对形态特征的表达会受到DEM数据分辨率的影响,进而造成表达结果的不确定性。尤其在黄土高原地区,地形特征更为破碎,地形要素更为复杂,其表达结果受DEM分辨率的影响更为明显。本文以黄土高原典型样区为例,基于点云数据建立不同分辨率的DEM数据集,通过不同地形因子对侵蚀沟特征进行表达,分析DEM分辨率在黄土侵蚀沟形态特征表达时的不确定性。结果显示,分辨率的降低对主沟支沟比和纵比降等侵蚀沟形态特征因子产生了较大影响,且指标与分辨率多呈现线性变化关系。但是,随着侵蚀沟的横向扩张,DEM分辨率对其特征表达的影响逐渐被削弱。此外,在使用固定分析窗口进行侵蚀沟特征计算时,由于分辨率的降低,格网尺寸增大,其实际分析半径随之增大,使得计算范围内地表形态变化增加,导致沟谷切割深度随着分辨率的降低反而增加。同时,侵蚀沟主沟道区域受分辨率影响较小,沟头区域指标与分辨率的关系较弱。
李思进 , 代文 , 熊礼阳 , 汤国安 . DEM分辨率对黄土侵蚀沟形态特征表达的不确定性分析[J]. 地球信息科学学报, 2020 , 22(3) : 338 -350 . DOI: 10.12082/dqxxkx.2020.190352
Terrain expression of loess erosional gully is the base of the researches of gully erosion modeling and prediction, which also have a great significance in related fields of geoscience. The quantitative study of gully features based on Digital Elevation Model (DEM) can contribute to the research of morphological change and formation process of erosional gully. Currently, the use of representative feature indicators to describe the morphology of loess erosional gully should be one of the most popular used methods in researches of erosional gully. However, due to the structural limitation of grid DEM, the uncertainty widely exists in the calculated results based on DEMs. In previous practical researches, it has been proved that the resolution of DEM is an important factor which can influence experimental results obviously and cause the uncertainty of feature derivatives. Especially in the area of the Loess Plateau, the fractured landform and complicated landscape elements influence the expression of morphological features. Thus, the impact of DEM's resolution are more obvious in this area. The aim of this study is to analyze the uncertainty of morphological feature expression in the Loess Plateau based on DEMs with different resolutions. In this paper, DEMs with various resolutions of three study areas in the Loess Plateau were established based on the point cloud data which were acquired by Unmanned Aerial Vehicle (UAV). Eight typical morphological indicators were selected and calculated based on DEMs. These indicators were divided into groups according to the definition of each indicator. Two groups were established to express the morphological features of gully channel and gully head respectively. The experimental results shown that DEM's resolution has great influences on morphological feature indicators of erosional gully, and the major relationships between indicators and resolutions are linear. The high development stage of erosional gully's horizontal extension can weaken the influence of DEM’s resolution on morphological feature expression. In addition, when using fixed-size windows to calculate morphological feature indicators of erosional gully, the decrease of DEM's resolution lead to the increase of actual analysis radius and then surface morphological change has a growth trend in calculation areas. This phenomenon results in the rise of gully cutting depth when using DEM with lower resolution. Besides, the main gully channel is less affected by resolution. Thus, the DEM data with low resolution can be used to calculate morphological features of main gully channel. Finally, the morphological indicators of gully head were analyzed and there are weak correlations between these indicators and the resolution of DEM.
表1 各样区沟谷网络提取适宜阈值Tab. 1 The appropriate threshold value for gully network extraction of sample areas (m) |
样区 | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | |
麻地沟 | 350 | 200 | 100 | 80 | 70 | 60 | 50 | 40 | 40 | 40 |
安塞 | 350 | 200 | 150 | 120 | 100 | 100 | 80 | 70 | 60 | 50 |
桥沟 | 350 | 150 | 100 | 80 | 80 | 70 | 60 | 50 | 50 | 50 |
表2 样区基本信息及特征概述Tab. 2 Basic information and features of study areas |
样区 | 位置 | 面积/km2 | 海拔/m | 侵蚀沟特点 |
---|---|---|---|---|
安塞 | 37°14'24"N—37°14'27"N,109°14'41"E—109°14'53"E | 0.50 | 1163.7~1416.5 | 主沟道呈东西走向,南面浅沟和切沟发育多,北面下切侵蚀强烈,发育3条较大的切沟,较少发育浅沟 |
麻地沟 | 37°28'59"N—37°28'49"N,108°48'2"E—108°48'35"E | 0.23 | 1396.8~1556.8 | 主沟道呈南北走向,浅沟和切沟发育较多 |
桥沟 | 37°34'10"N—37°34'16"N,104°16'49"E—104°16'57"E | 0.13 | 900.9~1017.1 | 主沟道呈西南—东北走向,两侧发育有较多浅沟和切沟 |
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