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利用数字高程模型(DEM)实现坡耕地数据的自动提取和侵蚀状况调查,并与实地勘察及相关研究结果进行对比,分析利用中低分辨率DEM提取坡耕地坡度信息误差的来源及其对水土流失调查结果的影响。结果表明:利用忠县1∶50000地形图生成分辨率为25m的DEM,基于该分辨率DEM自动提取的坡耕地信息在评价其水土流失现状时与实地勘察和相关研究结果存在一定差异,其主要原因为:①该地区地貌特殊,平行岭谷地貌和出露的侏罗纪紫色泥(页)岩与砂岩互层结构共同作用形成的地形较为复杂,造成该区土地利用多以小地块为主的镶嵌结构,而分辨率较低的DEM对地形起伏的描述误差较大;②人为修建的梯田(水田)、坎田以及垄沟整地措施对坡耕地微观地形改变的影响较大。因此,在坡耕地水土流失现状评价中,单从中低分辨率DEM获取坡度信息来判断水土流失程度,将会产生较大误差。DEM分辨率越高,对与坡度有关的地貌和水文参数的描述越精确,提取的坡度信息越准确。中低分辨率坡度可以通过变换,使其接近较高分辨率坡度对地形起伏的反映能力。此外,还应加强实地勘察力度,并与计算机自动提取技术相结合,才是正确评价坡耕地水土流失的方法。
The investigation of automatic extraction and erosion of sloping farmland was carried out by digital elevation model (DEM), and compared with the results of field survey and related research. The sources of information error of sloping farmland slope extraction using medium and low resolution DEM and its influence on soil erosion The impact of the survey results. The results showed that the DEM with a resolution of 25m was generated from 1: 50000 topographic map of Zhongxian. The slope farmland information automatically extracted based on this resolution DEM had some differences from the field survey and related research in evaluating the status of soil and water loss. The reasons are as follows: ① The terrain formed by the special landform, parallel ridge landscape and exposed Jurassic purple mudstone (sheet) rock and interbedded sandstone is more complicated in this area, resulting in more land use in this area Main mosaic structure, and the DEM with lower resolution has a greater error in description of the terrain relief. (2) The man-made terraced fields (paddy fields), ridge fields and ditch land preparation measures have a great influence on the micro-topographic changes of sloping fields. Therefore, in assessing the current status of soil and water loss on sloping farmland, the accuracy of water and soil loss can be judged by simply obtaining slope information from medium and low resolution DEMs. The higher the DEM resolution, the more accurate is the description of the geomorphic and hydrological parameters associated with the slope, and the more accurate the extracted slope information. Medium and low resolution slopes can be transformed to reflect near-high-resolution slopes on the relief of the terrain. In addition, the intensity of field investigation should be strengthened and combined with the automatic computer extraction technology, which is the correct way to evaluate the soil and water loss on sloping fields.