GEE代码实例教程详解：年度和月度土地覆盖变化分析

// 定义研究点坐标
var cor = [49.349581955929196, 37.390543498162955];
var loc = ee.Geometry.Point(cor);

// 加载FAO GAUL数据集并筛选研究区域
var roi = ee.FeatureCollection("FAO/GAUL/2015/level1").filterBounds(loc);
Map.centerObject(roi);
Map.addLayer(roi);

// 加载Google Dynamic World土地覆盖数据集
var map = ee.ImageCollection("GOOGLE/DYNAMICWORLD/V1")
  .filterDate('2023', '2024')
  .filter(ee.Filter.calendarRange(1, 12, 'month'))
  .filterBounds(roi);

// 计算年度土地覆盖
var annual_map = map.select('label').mode();
var VIS_PALETTE = [
  '419bdf', '397d49', '88b053', '7a87c6', 'e49635', 'dfc35a', 'c4281b',
  'a59b8f', 'b39fe1'
];

Map.addLayer(annual_map.clip(roi), {min: 0, max: 8, palette: VIS_PALETTE}, 'map2013', false);

// 导出年度土地覆盖图像
Export.image.toDrive({
  image: annual_map.clip(roi),
  description: 'annual_map',
  scale: 30,
  maxPixels: 1e13,
  region: roi,
  crs: annual_map.getInfo().crs
});

// 定义时间序列集合函数
function temporal_collection(collection, start, count, interval, unit) {
  var seq = ee.List.sequence(0, ee.Number(count).subtract(1));
  var origin_date = ee.Date(start);
  return ee.ImageCollection(seq.map(function (i) {
    var start_date = origin_date.advance(ee.Number(interval).multiply(i), unit);
    var end_date = origin_date.advance(ee.Number(interval).multiply(ee.Number(i).add(1)), unit);
    return collection.filterDate(start_date, end_date).mode()
      .set('system:time_start', start_date.millis())
      .set('system:time_end', end_date.millis());
  }));
}

// 创建月度土地覆盖集合
var monthly = temporal_collection(map.select('label'), '2023', 12, 1, 'month');

Map.addLayer(monthly.toBands().clip(roi), [], 'monthly_map', false);

// 更新月度土地覆盖图像的波段名称
var monthly_updated = monthly.map(function (img) {
  var date = img.date().format('YYYY-MM-dd');
  return img.rename(date);
});

print(monthly_updated.toBands());

// 导出月度土地覆盖图像
Export.image.toDrive({
  image: monthly_updated.toBands().clip(roi),
  description: 'monthly_lc',
  scale: 30,
  maxPixels: 1e13,
  region: roi,
  crs: monthly_updated.toBands().getInfo().crs
});