LARGE-SCALE CARTOGRAPHIC REPRESENTATION OF RELIEF FEATURES FROM SANDYZATION PROCESS

Abstract: In topographic maps, contour lines and elevation points usually represent the variation of height and slope. Contour lines interval defines the level of detail for relief representation. Geomorphological features we can identify on maps are related to contour lines generalization. In this study, we aim to define the necessary level of detail for the cartographic representation of relief features from the sandyzation process. The methodology comprises: defining the relief features associated with sandyzation at the study area by literature review; describing the aspects of data survey using Remotely Piloted Aircraft (RPA) to generate the orthophoto mosaic and the Digital Surface Model (DSM); and using the DSM to extract contour lines at different scales. We defined eight relief features (denudational landform, rill, ravine, micro-residual hill, dune, depositional fan, concentrated flow, and gully) for contour cartographic representation at 1:5,000, 1:1,000, 1:500, 1:200, and 1:100 scales. The results show the scales in which the relief features have their geomorphological characteristics better represented by contours lines. Since there is no reference for suitable scales for the cartographic representation of landforms related to the sandyzation process, this study can contribute to geomorphological researches in areas where this process occurs.

摘要：在地形图中，等高线与高程点通常用于表征高程与坡度的变化。等高距决定了地貌表示的细节程度。地图上可识别的地貌特征与等高线制图综合密切相关。本研究旨在明确沙化过程相关地貌特征在制图表达中所需的细节层级。研究方法包括：通过文献综述明确研究区内与沙化过程相关的地貌特征；阐述采用遥控驾驶航空器（Remotely Piloted Aircraft, RPA）开展数据采集以生成正射影像镶嵌图与数字表面模型（Digital Surface Model, DSM）的相关环节；以及基于DSM提取不同比例尺下的等高线。本研究针对1:5000、1:1000、1:500、1:200及1:100五种比例尺下的等高线制图表达，确定了8类地貌特征：剥蚀地貌、细沟、沟壑、微型残丘、沙丘、沉积扇、集中径流与冲沟。研究结果明确了可通过等高线更好地表征其地貌特征的比例尺区间。由于目前尚无沙化过程相关地貌的制图表达适宜比例尺参考依据，本研究可为沙化分布区的地貌学研究提供参考。