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基于无人机图像的戈壁表面砾石特征变化研究

Spatial Distribution of Gravel Characteristics on Gobi Desert Surface Based on Image Acquired by Unmanned Aerial Vehicle

  • 摘要:
    目的 通过无人机平台和运动结构建模技术获取了覆盖较大范围的戈壁表面正射图像和数字地面模型, 以位于新疆维吾尔自治区哈密市天山南坡的洪积扇为研究对象, 进行戈壁表面砾石覆盖度和粒径的测量及分析, 探讨利用无人机和图像处理技术进行大范围戈壁砾石研究的适用性。
    方法 通过自洪积扇扇心到靠近扇缘选取3个典型样区, 利用无人机获取连续覆盖的戈壁表面高分辨率图像, 生成了戈壁表面的高清正射拼接图像以及高精度的地形数据, 并提取了样区内砾石(粒径≥ 7 mm)的覆盖度及砾石(粒径≥ 32 mm)的粒径。
    结果 自扇心到靠近扇缘, 3个样区的砾石覆盖度分别为34.22%, 26.85%, 21.88%;砾石粒径均值分别为130, 95, 78 mm。随海拔下降, 样区总体砾石覆盖度和粒径均呈下降趋势, 且自扇中到扇缘相比自扇心到扇中下降趋势有所减缓; 而在各个样区内部, 砾石覆盖度及粒径与海拔关系不明显。
    结论 在洪积扇尺度上, 砾石覆盖度与粒径变化主要受海拔影响; 在样区尺度上, 砾石覆盖度和粒径变化则可能受到植被分布和局部地形的影响。利用无人机和图像处理技术, 可以高效且准确地评估大范围戈壁表面砾石特征及分布, 为戈壁形成演化研究提供基础数据及技术支撑。

     

    Abstract:
    Objective To explore the applicability of using unmanned aerial vehicle (UAV) and image processing technique for large scale research of gravels on Gobi surface.
    Method Taking the pluvial fan at south slope of Tianshan Mountains in Hami of Xinjiang Uygur Autonomous Region as study area, the orthographic images and digital terrain models (DTM) covering a large range of Gobi were obtained by UAV platform and the structure from motion (SfM) technology, and the gravel coverage and diameter were measured and analyzed. From the center to near the edge of the pluvial fan, three typical sample zones were selected, and high resolution images of Gobi surface were shot by camera on UAV. High resolution mosaic image and terrain data of Gobi surface were produced, and the coverage of gravels (diameter ≥ 7 mm) and diameter of gravels (diameter ≥ 32 mm) were calculated.
    Result From center to near the edge of the fan, the gravel coverage of the three sample zones was 34.22%, 26.85% and 21.88%, and the mean gravel diameter was 130, 95 and 78 mm. As elevation decreased, the gravel coverage and diameter dropped. The gravel coverage and diameter dropped more slowly from the middle to near the edge of the fan than from the center to the middle of the fan. However, within each sample zone, the relationship between gravel characteristics (coverage and diameter) and elevation was not obvious.
    Conclusion On the scale of pluvial fan, the changes of gravel coverage and diameter are mainly affected by elevation. On the scale of sample zone, the change of gravel coverage and diameter may be affected mainly by the vegetation distribution and local topography. Using UAV and image processing technology can efficiently and accurately estimate a wide range of the gravel characteristics and their spatial distribution, which provides basic data and methodological support for the research on Gobi evolution.

     

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