基于 GEE 可视化鄱阳湖近年变化

目录

1 完整代码

2 运行结果

1 完整代码

function maskS2clouds(image) {
  var qa = image.select('QA60')
  var cloudBitMask = 1 << 10;
  var cirrusBitMask = 1 << 11;
  var mask = qa.bitwiseAnd(cloudBitMask).eq(0).and(
             qa.bitwiseAnd(cirrusBitMask).eq(0))
  return image.updateMask(mask).divide(10000)
      .select("B.*")
      .copyProperties(image, ["system:time_start"])
}

var start = '2016-01-01'
var end = '2021-01-01'
var image = s2.filterDate(start, end)
              .filter(ee.Filter.lt('CLOUD_COVERAGE_ASSESSMENT',10))
              .filterBounds(roi)
              .map(function(image) {
                   var time_start = image.get("system:time_start")
                   image = image.multiply(0.0001)
                   image = image.set("system:time_start", time_start)
                   return image
              })

print(image)//会发现有很多元素，这是因为每年不止一副影像，我们要做的就是将每年的一幅放在一个集合里生成新的imagecollection

var yearList = ee.List.sequence(ee.Date(start).get("year"), ee.Number(ee.Date(end).get("year").subtract(1)));
 
var yearImgList = yearList.map(function(year) {
                              year = ee.Number(year)
                              var sdate = ee.Date.fromYMD(year, 1, 1)
                              var edate = ee.Date.fromYMD(year.add(1), 1, 1)
                              var tempCol = image.filterDate(sdate, edate)
                              var img = tempCol.median().clip(roi)
                              img = img.set("year", year)
                              img = img.set("system:index", ee.String(year.toInt()))
                              
                              return img
                              })
 
var imgCol = ee.ImageCollection.fromImages(yearImgList);

var params = {
  crs: 'EPSG:3857',
  framesPerSecond: 1,//帧率
  region: roi,
  min: 0.0,
  max: 0.3,
  bands: ['B8','B4','B3'],//选择假彩色
  dimensions: 512,
};

print(ui.Thumbnail(imgCol, params))//直接在控制台生成GIF
print(imgCol.getVideoThumbURL(params))//生成网址

Map.centerObject(roi)
Map.addLayer(image.median().clip(roi),{bands:['B8','B4','B3'],min:0,max:0.3})

2 运行结果