下载DEM格栅数据DEM数据的可获取性极其友好,在不同网站上有不同精度和瓦片范围的tiff图可供免费下载。其中覆盖范围最广,使用最为频繁的是ASTER卫星的Global Digital Elevation Model数据。废话不说,上连接:1)NASA:https://search.earthdata.nasa.gov/search?gdf=GeoTIFF!ArcGIS
在搜索栏搜索 ASTER,使用框选工具选择下载范围即可获取。2)SRTM DATA:https://srtm.csi.cgiar.org/srtmdata/中科院镜像全球DEM30m精度格栅tiff文件下载镜像连接。无脑选择之后搜索,直接跳转网页下载。这个数据的优势在于他的瓦片面积很大,在进行大面积分析时非常好用,免除了在GIS中用Mosaic to new raster进行拼贴的繁琐步骤。
纽约数据直接选择下载zip压缩包解压即可,维州数据需要留下自己的邮箱等网站工作人员给你发链接。(1)-(3)三个网站上下载的DEM瓦片都是矩形格栅,而局部地区的数据下载基本都会切分好行政边界。所以在地区官网下载DEM的第一个好处是不需要你再下载行政区Polygon数据进行Extract by mask操作。其次,地区官网的数据精度往往更高,例如纽约数据的格栅精度达到了1英尺(约0.3m,这里顺路吐槽下美国人讨厌的英制单位),澳大利亚的维州数据精度也达到了10m。
后两个斜率表达大家可能有些陌生,ESRI对斜率方向曲率和垂直斜坡方向曲率的解释如下:Profile Curvature: Profile curvature is parallel to the direction of the maximum slope. A negative value (figure A) indicates that the surface is upwardly convex at that cell. A positive profile (figure B) indicates that the surface is upwardly concave at that cell. A value of zero indicates that the surface is linear (figure C) Profile curvature affects the acceleration or deceleration of flow across the surface.
Planform Curvature: Planform curvature (commonly called plan curvature) is perpendicular to the direction of the maximum slope. A positive value (figure A) indicates the surface is sidewardly convex at that cell. A negative plan (figure B) indicates the surface is sidewardly concave at that cell. A value of zero indicates the surface is linear (figure C) Profile curvature relates to the convergence and divergence of flow across a surface.