feat(GEE_Scripts): 新增土地覆盖分类数据下载脚本.
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GEE_Scripts/LULC_download.js
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GEE_Scripts/LULC_download.js
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/**
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* 土地覆盖分类数据下载
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*
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* @author CVEO Team
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* @date 2025-10-27
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*
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* 1. 加载 ESA WorldCover, Dynamic World 等公开土地覆盖数据
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* - ESA WorldCover 2021 V200 版本: 11 类地物
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* - Dynamic World V1 版本: 9 类地物
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* 2. 加载 Sentinel-2 数据
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* 3. 导出 COG 云优化并填补缺失值的 GeoTIFF 影像 (大区域 GEE 自动分块下载)
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*/
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// 加载研究区域和影像
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// var region_name = "武汉市";
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// var region_name_en = "Wuhan";
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// var region = allCites.filter(ee.Filter.eq("市", region_name));
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var region_name = "49REL";
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var region_name_en = region_name;
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var region = grid;
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var year = 2025;
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var start_date = year + "-01-01";
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var end_date = year + "-12-31";
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var target_month = 5; // 指定月份
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var cloud_threshold = 60;
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// Use 'cs' or 'cs_cdf', depending on your use case; see docs for guidance.
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var QA_BAND = "cs_cdf";
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// The threshold for masking; values between 0.50 and 0.65 generally work well.
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// Higher values will remove thin clouds, haze & cirrus shadows.
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var CLEAR_THRESHOLD = 0.7;
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// Sentinel-2的B8A波段(20m)可能更适合代表近红外波段
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// var s2Bands = ["B2", "B3", "B4", "B8", "B11", "B12"];
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var s2Bands = ["B2", "B3", "B4", "B8A", "B11", "B12"];
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var commonBands = ["Blue", "Green", "Red", "NIR", "SWIR1", "SWIR2"];
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var bounds = region.geometry().bounds();
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var common_filter = ee.Filter.and(
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ee.Filter.bounds(bounds),
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ee.Filter.date(start_date, end_date)
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);
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/**
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* 基于 Cloud Score+ 云掩膜
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* @param {ee.Image} image Sentinel-2 image
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* @return {ee.Image} cloud masked Sentinel-2 image
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*/
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function maskS2cloudsByCS(image) {
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var cloudMask = image.select(QA_BAND).gte(CLEAR_THRESHOLD);
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image = image.updateMask(cloudMask);
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return image
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.copyProperties(image)
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.copyProperties(image, ["system:time_start", "system:index", "system:id"]);
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}
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/**
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* 按照属性值对影像集合进行排序
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* @param {ee.ImageCollection} collection 影像集合
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* @param {ee.Geometry} region 目标区域
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* @return {ee.ImageCollection} 排序后的影像集合
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*/
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function sortedByPriority(collection, region) {
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// 1. 计算每张影像的有效像素 (非空像素) 覆盖面积
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var withArea = collection.map(function (image) {
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var area = image
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.mask()
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.reduceRegion({
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reducer: ee.Reducer.sum(),
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geometry: region,
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scale: 10,
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maxPixels: 1e9,
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})
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.values()
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.get(0);
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return image.set("coverage_area", area);
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});
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// 2. 剔除覆盖面积为 0 的影像
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withArea = withArea.filter(ee.Filter.gt("coverage_area", 0));
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// 3. 根据云量 (降序) 和覆盖率 (升序) 对影像进行综合排序
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// 考虑影像集合是以栈的形式 (先入后出) 组织的, 在进行 mosaic 合成时, 从最后一张影像开始合并, 逆转排序
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// sort 默认升序 True
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var sorted = withArea
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.sort("CLOUDY_PIXEL_PERCENTAGE", false)
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.sort("coverage_area");
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return ee.ImageCollection(sorted);
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}
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// 加载Sentinel-2 L2A数据
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// Cloud Score+ image collection.
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// Note Cloud Score+ is produced from Sentinel-2 level 1C data and can be applied to either L1C or L2A collections.
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var S2csPlus = ee.ImageCollection("GOOGLE/CLOUD_SCORE_PLUS/V1/S2_HARMONIZED");
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var S2dataset = ee
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.ImageCollection("COPERNICUS/S2_SR_HARMONIZED")
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.filter(common_filter)
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.filter(ee.Filter.lt("CLOUDY_PIXEL_PERCENTAGE", cloud_threshold))
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.select(s2Bands, commonBands)
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.linkCollection(S2csPlus, [QA_BAND])
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.map(maskS2cloudsByCS);
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var target_s2 = sortedByPriority(
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S2dataset.filter(
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ee.Filter.calendarRange(target_month, target_month, "month")
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),
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region
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);
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var s2_img = ee.Image(target_s2.median());
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// 加载ESA WorldCover数据
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var ESA_worldcover = ee.ImageCollection("ESA/WorldCover/v200").first();
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var wc_img = ee.Image(ESA_worldcover.clip(region));
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var wc_class_names = {
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"Tree cover": 10,
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Shrubland: 20,
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Grassland: 30,
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Cropland: 40,
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"Built-up": 50,
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"Bare / sparse vegetation": 60,
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"Snow and ice": 70,
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"Permanent water bodies": 80,
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"Herbaceous wetland": 90,
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Mangroves: 95,
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"Moss and lichen": 100,
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};
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// 统计各类别覆盖面积
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var wc_class_area = wc_img
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.reduceRegion({
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reducer: ee.Reducer.frequencyHistogram(),
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geometry: region,
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scale: 10,
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maxPixels: 1e13,
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})
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.get("Map");
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print("ESA WorldCover 2021 v200");
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print("各类别名称:", wc_class_names);
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print("各类别覆盖面积:", wc_class_area);
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// 加载Dynamic World数据
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var DWdataset = ee
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.ImageCollection("GOOGLE/DYNAMICWORLD/V1")
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.filter(common_filter)
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.select("label");
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// mode() 取出现次数最多的类别作为合成后的类别
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var dw_img = ee.Image(DWdataset.mode().clip(region));
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var dw_class_names = {
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water: 0,
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trees: 1,
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grass: 2,
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flooded_vegetation: 3,
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crops: 4,
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shrub_and_scrub: 5,
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built: 6,
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bare: 7,
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snow_and_ice: 8,
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};
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var built_img = dw_img.updateMask(dw_img.eq(dw_class_names.built));
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var crop_img = dw_img.updateMask(dw_img.eq(dw_class_names.crops));
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var flood_img = dw_img.updateMask(dw_img.eq(dw_class_names.flooded_vegetation));
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// 统计各类别覆盖面积
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var dw_class_area = dw_img
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.reduceRegion({
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reducer: ee.Reducer.frequencyHistogram(),
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geometry: region,
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scale: 10,
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maxPixels: 1e13,
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})
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.get("label");
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print("Dynamic World v1");
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print("各类别名称:", dw_class_names);
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print("各类别覆盖面积:", dw_class_area);
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var VIS_PALETTE = [
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"419bdf",
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"397d49",
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"88b053",
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"7a87c6",
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"e49635",
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"dfc35a",
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"c4281b",
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"a59b8f",
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"b39fe1",
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];
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var DW_vis = {
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min: 0,
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max: 8,
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palette: VIS_PALETTE,
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};
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var true_rgb_vis = {
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bands: ["Red", "Green", "Blue"],
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min: 0.0,
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max: 3000,
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};
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var false_rgb_vis = {
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min: 0.0,
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max: 4000,
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gamma: 1.4,
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bands: ["NIR", "Red", "Green"],
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};
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var styling = {
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color: "red",
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fillColor: "00000000",
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};
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var WC_vis = {
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bands: ["Map"],
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};
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Map.centerObject(region, 9);
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Map.addLayer(region.style(styling), {}, region_name);
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Map.addLayer(wc_img, WC_vis, "ESA 2021 Landcover");
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Map.addLayer(dw_img, DW_vis, "Dynamic World LULC");
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Map.addLayer(
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s2_img,
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true_rgb_vis,
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year + "-" + target_month + " Sentinel-2 True RGB",
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false
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);
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Map.addLayer(
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s2_img,
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false_rgb_vis,
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year + "-" + target_month + " Sentinel-2 False RGB",
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false
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);
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// Map.addLayer(built_img, DW_vis, 'Built DW LULC');
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// Map.addLayer(crop_img, DW_vis, "Crop DW LULC");
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// Map.addLayer(flood_img, DW_vis, "Flood DW LULC");
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// 导出裁剪处理后的土地覆盖数据
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var fileName = region_name_en + "_ESA_WorldCover_2021_v200";
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// 区域过大, 需要先将 wc_img 划分为四块网格分开下载
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var bounds = region.geometry().bounds();
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var coords = ee.List(bounds.coordinates().get(0));
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var minX = ee.Number(ee.List(coords.get(0)).get(0));
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var minY = ee.Number(ee.List(coords.get(0)).get(1));
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var maxX = ee.Number(ee.List(coords.get(2)).get(0));
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var maxY = ee.Number(ee.List(coords.get(2)).get(1));
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var midX = minX.add(maxX).divide(2);
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var midY = minY.add(maxY).divide(2);
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var grid1 = ee.Geometry.Rectangle([minX, minY, midX, midY]);
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var grid2 = ee.Geometry.Rectangle([midX, minY, maxX, midY]);
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var grid3 = ee.Geometry.Rectangle([minX, midY, midX, maxY]);
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var grid4 = ee.Geometry.Rectangle([midX, midY, maxX, maxY]);
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var grids = [grid1, grid2, grid3, grid4];
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for (var i = 0; i < grids.length; i++) {
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var grid_region = grids[i];
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var clipped_img = wc_img.clip(grid_region);
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var grid_fileName = fileName + "_grid_" + (i + 1);
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Export.image.toDrive({
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image: clipped_img,
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description: grid_fileName,
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folder: "LULC",
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region: grid_region,
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scale: 10,
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maxPixels: 1e13, // GEE 最多支持 1e8 像素, 当超过时会自动分块
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fileFormat: "GeoTIFF",
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// 导出COG云优化的GeoTIFF影像
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formatOptions: {
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cloudOptimized: true,
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},
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});
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}
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