PIE-engine 教程 ——全球夜间灯光指数动画加载含ui.legend图例添加

本次我们要使用到的影像时全球夜间灯光数据集，VIIRS_VCMCFG/NIGHTTIME_LIGHTS

新一代对地观测卫星Suomi NPP,搭载的可见光红外成像辐射仪（Visible Infrared Imaging Radiometer Suit,VIIRS），能够获取新的夜间灯光遥感影像（Day/Night Band,DNB波段）。VIIRS_VCMCFG夜光遥感数据的空间分辨率为750m，准确地记录了夜光辐射强度，相比DMSP/OLS能够探测到更微弱的灯光辐射。

时间范围时2012年至今——

波段信息：

本教程需要用到的函数：

代码：

  

   

    

     

    
    

     

      //加载全球国家行政区划边界数据
     
    
   

    

     

    
    

     

      var roi = pie
     
    
   

    

     

    
    

     

        .FeatureCollection("RESDC/WORLD_COUNTRY_BOUNDARY")
     
    
   

    

     

    
    

     

        .filter(pie.Filter.eq("fcname", "中国"));
     
    
   

    

     

    
    

     

      visroi = { color: "ff0000ff", fillColor: "00000000", width: 1 };
     
    
   

    

     

    
    

     

      Map.addLayer(roi, visroi, "中国", false);
     
    
   

    

     

    
    

     

      var chn = roi.getAt(0).geometry();
     
    
   

    

     

    
    

     

      //定位地图中心
     
    
   

    

     

    
    

     

      Map.centerObject(chn, 3);
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      //设置夜光数据预览参数及颜色组合
     
    
   

    

     

    
    

     

      var colors = [
     
    
   

    

     

    
    

     
  "#000000",
     
    
   

    

     

    
    

     
  "#4c3300",
     
    
   

    

     

    
    

     
  "#664401",
     
    
   

    

     

    
    

     
  "#7f5501",
     
    
   

    

     

    
    

     
  "#996601",
     
    
   

    

     

    
    

     
  "#b27702",
     
    
   

    

     

    
    

     
  "#cc8802",
     
    
   

    

     

    
    

     
  "#e59902",
     
    
   

    

     

    
    

     
  "#ffad02",
     
    
   

    

     

    
    

     
  "#ffaf02",
     
    
   

    

     

    
    

     
  "#ffb102",
     
    
   

    

     

    
    

     
  "#ffb302",
     
    
   

    

     

    
    

     
  "#ffb502",
     
    
   

    

     

    
    

     
  "#ffb702",
     
    
   

    

     

    
    

     
  "#ffb902",
     
    
   

    

     

    
    

     
  "#ffbb02",
     
    
   

    

     

    
    

     
  "#ffbd02",
     
    
   

    

     

    
    

     
  "#ffc002",
     
    
   

    

     

    
    

     
  "#ffc202",
     
    
   

    

     

    
    

     
  "#ffc402",
     
    
   

    

     

    
    

     
  "#ffc602",
     
    
   

    

     

    
    

     
  "#ffc801",
     
    
   

    

     

    
    

     
  "#ffca01",
     
    
   

    

     

    
    

     
  "#ffcc01",
     
    
   

    

     

    
    

     
  "#ffce01",
     
    
   

    

     

    
    

     
  "#ffd001",
     
    
   

    

     

    
    

     
  "#ffd201",
     
    
   

    

     

    
    

     
  "#ffd501",
     
    
   

    

     

    
    

     
  "#ffd701",
     
    
   

    

     

    
    

     
  "#ffd901",
     
    
   

    

     

    
    

     
  "#ffdb01",
     
    
   

    

     

    
    

     
  "#ffdd01",
     
    
   

    

     

    
    

     
  "#ffdf01",
     
    
   

    

     

    
    

     
  "#ffe101",
     
    
   

    

     

    
    

     
  "#ffe300",
     
    
   

    

     

    
    

     
  "#ffe500",
     
    
   

    

     

    
    

     
  "#ffe700",
     
    
   

    

     

    
    

     
  "#ffea00",
     
    
   

    

     

    
    

     
  "#ffec00",
     
    
   

    

     

    
    

     
  "#ffee00",
     
    
   

    

     

    
    

     
  "#fff000",
     
    
   

    

     

    
    

     
  "#fff200",
     
    
   

    

     

    
    

     
  "#fff400",
     
    
   

    

     

    
    

     
  "#fff600",
     
    
   

    

     

    
    

     
  "#fff800",
     
    
   

    

     

    
    

     
  "#fffa00",
     
    
   

    

     

    
    

     
  "#fffc00",
     
    
   

    

     

    
    

     
  "#ffff00",
     
    
   

    

     

    
    

     

      ];
     
    
   

    

     

    
    

     

      var visParams = {
     
    
   

    

     

    
    

     
  min: 0,
     
    
   

    

     

    
    

     
  max: 60,
     
    
   

    

     

    
    

     
  palette: colors,
     
    
   

    

     

    
    

     

      };
     
    
   

    

     

    
    

     

      //定义夜光指数计算函数
     
    
   

    

     

    
    

     

      function calcNT(night, chn) {
     
    
   

    

     

    
    

     
  var result = night.reduceRegion(pie.Reducer.mean(), chn, 1);
     
    
   

    

     

    
    

     
  return result;
     
    
   

    

     

    
    

     

      }
     
    
   

    

     

    
    

     

      //循环计算影像的夜光指数
     
    
   

    

     

    
    

     

      var xSeries = [];
     
    
   

    

     

    
    

     

      var chnNT = [];
     
    
   

    

     

    
    

     

      for (var i = 2013; i < 2021; i++) {
     
    
   

    

     

    
    

     
  var nightLight = pie
     
    
   

    

     

    
    

     

          .ImageCollection("VIIRS_VCMCFG/NIGHTTIME_LIGHTS")
     
    
   

    

     

    
    

     

          .filterDate(i + "-01-01", i + "-12-31")
     
    
   

    

     

    
    

     

          .map(function (image) {
     
    
   

    

     

    
    

     
      return image.select("avg_rad").divide(1000).rename("a_r");
     
    
   

    

     

    
    

     

          })
     
    
   

    

     

    
    

     

          .mean();
     
    
   

    

     

    
    

     
  Map.addLayer(nightLight, visParams, String(i), true);
     
    
   

    

     

    
    

     
  var chnresult = calcNT(nightLight, chn);
     
    
   

    

     

    
    

     

        xSeries.push(String(i));
     
    
   

    

     

    
    

     

        chnNT.push(chnresult);
     
    
   

    

     

    
    

     

      }
     
    
   

    

     

    
    

     

      //动画显示
     
    
   

    

     

    
    

     

      Map.playLayersAnimation(xSeries, 0.5, 100);
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      //添加图例
     
    
   

    

     

    
    

     

      var data = {
     
    
   

    

     

    
    

     
  title: "夜光指数",
     
    
   

    

     

    
    

     
  colors: colors,
     
    
   

    

     

    
    

     
  step: 30,
     
    
   

    

     

    
    

     

      };
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      //设定图例位置
     
    
   

    

     

    
    

     

      var style = {
     
    
   

    

     

    
    

     
  top: "80%",
     
    
   

    

     

    
    

     
  left: "40%",
     
    
   

    

     

    
    

     
  height: "70px",
     
    
   

    

     

    
    

     
  width: "350px",
     
    
   

    

     

    
    

     

      };
     
    
   

    

     

    
    

     

      var legend = ui.Legend(data, style);
     
    
   

    

     

    
    

     

      Map.addUI(legend);
     
    
  
 

我这里只节选其中一年的影像进行展示： 

 当然这里我们无法看出时哪一年的影像，我们可以添加一个label来完成相应图层的信息展示：

  

   

    

     

    
    

     

      var xSeries = [];
     
    
   

    

     

    
    

     
 
     
    
   

    

     

    
    

     

      var label = ui.Label("");
     
    
   

    

     

    
    

     

      label = label.setStyle({
     
    
   

    

     

    
    

     
  backgroundColor: "white",
     
    
   

    

     

    
    

     

      });
     
    
   

    

     

    
    

     

      Map.addUI(label);
     
    
   

    

     

    
    

     

      Map.playLayersAnimation(xSeries, 1, -1, function (name, index) {
     
    
   

    

     

    
    

     

        label = label.setValue("中国2000-2020年人口变化：" + name + "年");
     
    
   

    

     

    
    

     

      });
     
    
  
 

文章来源: blog.csdn.net，作者：此星光明，版权归原作者所有，如需转载，请联系作者。

原文链接：blog.csdn.net/qq_31988139/article/details/126940831