全国第一次水保普查野外调查单元的确定研究——基于不同比例尺地形图

为野外土壤侵蚀调查的工作人员提供直观精确的参考底图,确保全国第一次水保普查工作的顺利实施,对利用不同比例尺地形图确定水土保持普查单元的确切位置以及描绘单元边界线的方法进行了研究。结果表明：根据地形图分幅编号,制作出1∶10万、1∶5万、1.0∶2.5万和1∶1万四者的分幅关系图,通过图幅号结合分幅关系图,可迅速确定1∶1万地形图在1∶5万和1.0∶2.5万地形图中的准确位置,然后依据全国第一次水保普查工作标准结合1∶1万地形图就可方便的确定水保普查单元;单元边界描绘的关键在于准确划分山脊线,可利用地形图找到普查单元的至高点,根据山脊线高程值逐渐降低的特征,从至高点沿着等高线的最大曲率处描绘分界线。

The Determination of Field Investigation Unit based on Different Scale Topographic Map in the First National Water & Soil Conservation Survey

To provide accurate base map for the field investigation and to ensure the smooth implementation of the first national soil and water conservation survey.They were studied that the determine of the exact location for soil and water conservation unit in the different scale topographic maps and how to accurately decide and describe boundary.The results showed that： according to the framing code standard of the topographic maps,it was easily maked the framing relationship chart between the four kinds of map（1∶100000,1∶50000,1∶25000 and 1∶10000）.Combined the framing code with this chart,the accurate position of 1∶10000 topographic map could be quickly determined on the 1∶50000 and 1∶25000 topographic maps,then the water conservation survey unit was very conveniently detemined on the basis of the work procedure standard of the first national soil and water conservation survey and the 1∶10000 topographic map.The key to describe unit boundary was how to accurately find ridge line,it needed to find the highest point of the investigation unit on the topographic map,then to describe boundary along the biggest curvature part of the contours from the highest point,according to the elevation gradually reduce characteristics of the ridge line.