三维激光扫描技术在坡面微地形观测中的应用

发布时间：2018-08-11 17:04

【摘要】：地面三维激光扫描技术作为一种能够快速完整、精确地获得被测目标的点云数据,在微观尺度的侵蚀监测方面的应用逐渐广泛。微观地形由于地形表面起伏较小,降雨侵蚀后地形、地貌变化相对较小,若想对此类较小地形变化做出准确监测分析,则需要较高精度的观测仪器,三维激光扫描技术的高精度恰好能够满足侵蚀监测的要求。高密度点云可以完整描述坡面某一时刻的具体形态,相比于传统观测方式,三维激光扫描技术具有非接触性测量的特点,可保证微地形在测量过程不会因为观测过程而发生变化,对点云数据进行插值建模生成高精度的微地形DEM,能够准确定量的反映微地形的各种地形因子。研究采用野外小区:20cm深耕、10cm深耕、裸坡三种地形,每15天一次,累计观测4次的观测数据;室内小区20cm深耕、10cm深耕、裸坡、5cm细沟、10cm细沟、15cm细沟六种地形在40mm/h、90mm/h、120mm/h三种雨强条件下雨前、雨后的观测数据。采用地理信息相关软件对点云数据加以处理分析,提取不同尺度条件下各类微地形的坡度、坡向、坡度变化率和坡向变化率;对坡度、坡向定性研究微地形变化与观测尺度之间的相关性,对坡度变化率、坡向变化率的研究得出坡度、坡向的变化值域。得出结论当观测的地形坡度分布相对平缓时可以采用较低的分辨率进行观测,但对微地形坡度而言不能够采用20mm以下的观测尺度;坡向的变化则与观测尺度的相关性较小。选取深耕、裸坡两种地形条件下三种观测尺度变化的点云数据进行抽稀、加密处理,并且探讨抽稀加密处理后微地形地坡度、曲率、糙度的变化特征。得出结论针对于起伏较小的地形采用抽稀处理后计算曲率速率会提高,且精度不会降低;1mm的数据抽稀加密过程中糙度变化规律性很强,可以探索规律,建立抽稀尺度与糙度之间关系,通过抽稀提高数据的计算效率。对野外条件下20cm深耕、10cm深耕、裸坡三种地形每15天的观测结果;室内试验20cm深耕、10cm深耕、裸坡、5cm细沟、10cm细沟、15cm细沟六种地形在40mm/h、90mm/h、120mm/h三种雨强条件下雨前雨后的观测数据提取出雨前、雨后糙度微地形的糙度。得出野外地形条件下地形与糙度变化呈正相关,室内条件下雨强对于糙度影响十分复杂;裸坡在降雨强度变化的情况下糙度变化耕接近细沟而并非耕作地形,耕作地形糙度变化为先夷平而后产生侵蚀,而沟蚀则直接产生侵蚀现象。
[Abstract]:As a kind of point cloud data which can be obtained quickly and accurately, 3D laser scanning technology has been widely used in micro-scale erosion monitoring. Because of the small fluctuation of topographic surface, the topography and geomorphology change after rainfall erosion are relatively small. If we want to make accurate monitoring and analysis of this kind of smaller topographic change, we need a high precision observation instrument. The high accuracy of 3D laser scanning technology can meet the demand of erosion monitoring. High density point cloud can describe the specific shape of the slope at a certain time. Compared with the traditional observation method, 3D laser scanning technology has the characteristics of non-contact measurement. It can ensure that the microtopography will not change as a result of the observation process. The point cloud data can be interpolated to generate a high-precision micro-terrain DEM which can accurately and quantitatively reflect the various terrain factors of the micro-terrain. In this study, the observation data of 10 cm deep tillage and 10 cm deep tillage, 10 cm deep tillage and 10 cm deep tillage in indoor 20cm plot were studied. The observation data of six kinds of topographical features of 15 cm rill in 5 cm rill, 10 cm rill and 15 cm rill in 40 mm / h ~ 90 mm / h / h ~ 120 mm / h rain intensity before and after rain. The point cloud data are processed and analyzed by geographic information related software to extract the slope, slope direction, slope change rate and slope direction change rate of all kinds of microtopography under different scales. The correlation between the microtopography change and the observation scale is studied qualitatively. The variation range of slope and direction is obtained from the study of slope change rate and slope direction change rate. It is concluded that when the topographic gradient distribution is relatively smooth, the low resolution can be used, but the observation scale below 20mm can not be used for the micro-terrain slope, and the variation of slope direction is less correlated with the observation scale. The point cloud data of three kinds of observation scale changes under the condition of deep tillage and bare slope were selected to be thinned and encrypted, and the variation characteristics of slope, curvature and roughness of microtopography after thinning and infilling treatment were discussed. It is concluded that the calculation of curvature rate will be improved after thinning treatment, and the precision will not be reduced in the process of razing and encrypting the data with less undulation, so the regularity of roughness variation is very strong, and the law can be explored. The relationship between rawness scale and roughness was established, and the efficiency of data calculation was improved by thinning. The observation results of 20cm deep tillage 10cm deep tillage and bare slope three kinds of terrain were observed every 15 days under field conditions, and 20cm deep tillage 10cm deep tillage experiment was carried out in laboratory. Five cm rill, 10 cm rill, 15 cm rill, six topographical conditions: 40 mm / h, 90 mm / h, 120 mm / h, before and after rain, the roughness of the topography was obtained before and after the rain. The results show that there is a positive correlation between the roughness and the topography in the field, and the effect of strong rain on the roughness is very complicated, and the roughness change of bare slope is close to the ravine, but not the tillage, when the rainfall intensity is changing. The roughness of tillage is flattened first and then eroded, and erosion is directly caused by trench erosion.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P225.2;P217

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