Global 30m Height Above the Nearest Drainage
方法： methodology here
最近近排水口以上的高度（HAND）是一个使用最近的排水口进行归一化的数字高程模型，用于水文和更广泛的用途，如灾害测绘、地貌分类和遥感。HAND的基本特征之一是它能够捕捉当地环境中的异质性，否则难以测量或建模。虽然学术文献中发表了许多HAND的应用，但还没有生成和分析全球规模的HAND数据集，特别是使用更高分辨率的DEM，如新的、一角秒（约30米）分辨率的SRTM版本。在这项工作中，我们提出了第一个使用两个DEM的镶嵌计算的全球版本的HAND。SRTM（30米）和Viewfinder Panoramas DEM（90米）。较低分辨率的DEM被用来覆盖北纬60度以上的纬度，在那里SRTM是缺失的。为了并行处理，生成了新的HydroBASINS集水区的同质化、等面积版本。新的集水区边界被用来用D8方法划定DEM。用于计算HAND的方法是用PCRaster软件实现的，在谷歌计算引擎并行平台上运行。
Or get it from Global Height Above the Nearest Drainage (30m)
数据引用：
Donchyts, Gennadii, Hessel Winsemius, Jaap Schellekens, Tyler Erickson, Hongkai Gao, Hubert Savenije, and Nick van de Giesen. "Global 30m Height Above the Nearest Drainage (HAND)",
Geophysical Research Abstracts, Vol. 18, EGU2016-17445-3, 2016, EGU General Assembly (2016).
代码：
var hand30_100 = ee.ImageCollection("users/gena/global-hand/hand-100"), hand30_1000 = ee.Image("users/gena/GlobalHAND/30m/hand-1000"), hand90_1000 = ee.Image("users/gena/GlobalHAND/90m-global/hand-1000"), demSRTM = ee.Image("USGS/SRTMGL1_003"), demALOS = ee.Image("JAXA/ALOS/AW3D30/V2_2"); demALOS = demALOS.select('AVE_DSM') var paletteHand = ['023858', '006837', '1a9850', '66bd63', 'a6d96a', 'd9ef8b', 'ffffbf', 'fee08b', 'fdae61', 'f46d43', 'd73027']; var vis = {min: 1, max: 150, palette: paletteHand} Map.addLayer(hand30_100.mosaic(), vis, 'HAND 100, 30m (~0.1km2)', true) Map.addLayer(hand30_1000, vis, 'HAND 1000, 30m (~1km2)', false) Map.addLayer(hand90_1000, vis, 'HAND 1000, 90m (~8km2)', false) // add styled var utils = require('users/gena/packages:utils') function hillshade(image) { var weight = 0.7 var extrusion = 5 var sunAzimuth = 315 var sunElevation = 35 var contrast = 0.1 var brightness = 0 var saturation = 0.85 return utils.hillshadeRGB(image, demALOS, weight, extrusion, sunAzimuth, sunElevation, contrast, brightness, saturation) } Map.addLayer(hillshade(hand30_100.mosaic().visualize(vis)), {}, 'HAND 100, 30m (~0.1km2) hillshade', false) Map.addLayer(hillshade(hand30_1000.visualize(vis)), {}, 'HAND 1000, 30m (~1km2) hillshade', true) Map.addLayer(hillshade(hand90_1000.visualize(vis)), {}, 'HAND 1000, 90m (~8km2) hillshade', false) // clip potential flooded areas var palettes = require('users/gena/packages:palettes') var bigFlood = hand30_1000.resample('bicubic').multiply(-1).unitScale(-15, -5).selfMask() Map.addLayer(bigFlood, { palette: palettes.cb.Blues[7] }, 'water', true, 0.5)
30和90--细胞分辨率，100和1000--河头阈值的数量
30 and 90 - cell resolution, 100 and 1000 - number of river head threshold cells
代码链接：
Shared License: This work is licensed under a Creative Commons Attribution 4.0 International License. You are free to copy and redistribute the material in any medium or format, and to transform and build upon the material for any purpose, even commercially. You must give appropriate credit, provide a link to the license, and indicate if changes were made.
Source and Curated by: Donchyts/Deltares
Keywords: Global Hand, Hydrology, drainage
Last updated: ~2017
