基于GPS不同测量间距的DEM地形信息提取沟蚀参数对比

GPS技术正在成为一种快速高效研究沟蚀发生演变的手段。但由于GPS测量间距的影响，从建立的不同尺度DEM上获取的地形信息存在很大的不确定性，影响沟蚀研究的准确性。本文以长江上游西昌地区马家松坡小流域作为试验样区，利用RTK—GPS技术，按测量间距3，5，10m和20m等4种空间尺度对小流域的地形进行测量，基于ArcGIS 8．2地理信息系统软件，建立相关尺度的栅格DEM，提取地面坡度、剖面曲率以及沟壑密度等地形信息。研究结果表明，随着测量间距的增加，从DEM上提取地面平均坡度、平均剖面曲率和沟壑密度均呈显著线性递减趋势，5m的测量间距是长江上游地区描述地形的理想尺度，可以满足研究冲沟和切沟的需要，而3m及3m以下的测量间距适用于细沟、浅沟的研究需要。我们的研究结果对应用GPS技术，实现高精度快速确定地表沟蚀过程方面具有重要意义。

Comparison of Topographic-Related Parameters Through Different GPS-Survey Scales in Gully Catchmnent of Upper Yangtze River Basin

GPS-survey technology is becoming an effective tool for determining topographic-related parameters. We hypothesized that the topographic-related parameters extracted from different scales of GPS survey are uncertain and the uncertainty will be especially large with respect to gully-related parameters. Four GPS-survey scales of 3, 5, 10, and 20-meter grid were conducted in Majiasongpo gully catchment located in Xichang area, SW-China. Topographic parameters including slope gradient, profile curvature, and gully system were derived from grid DEMs established using ArcGIS 8. 2 software. The results indicated that the average slope gradient and average profile curvature and gully density significantly decreased with the increase of GPS-survey grid, suggesting a lower value of gully-related parameters with big GPS-survey grid than with small GPS-survey grid. A GPS-survey scale of 5 m grid is suitable for establishing DEMs in quantifying gully-related parameters whereas a 3 or less than 3 m GPS-survey scale can meet with study needs of rills and shallow gullies in the upper Yangtze River basin.