生态遥感的学习笔记

GEE提取感兴趣区的时间序列

2020-04-23  本文已影响0人  荔枝猪

案例一:提取一个点的FPAR时间序列

// define a region of interst as a buffer around a point
var study = ee.Geometry.Point(116.667,43.53).buffer(1000);
// show region of interst
Map.centerObject(study,4);
Map.addLayer(study,{},'study');
// load MODIS image
var image = ee.ImageCollection('MODIS/006/MOD15A2H')
    .filterDate('2002-01-01', '2010-12-31')
    .filterBounds(study)
    .select('Fpar_500m');
// create the chart
var chart = ui.Chart.image.series({
  imageCollection: image, 
  region: study, 
  reducer: ee.Reducer.mean(),
  scale: 1000
});
// print the chart
print(chart);

案例二:提取数个点的GPP

// define a region of interst as a buffer around a point
var YY = ee.Feature( ee.Geometry.Point(112.93, 29.53).buffer(1000), {label: 'YY'});
var AQ = ee.Feature( ee.Geometry.Point(116.98, 30.48).buffer(1000), {label: 'AQ'});
var study = new ee.FeatureCollection([YY,AQ]);
// show region of interste
Map.centerObject(study,4);
Map.addLayer(study,{},'study');
// load MODIS data 
var collection = ee.ImageCollection('MODIS/006/MOD17A2H')
    .filterDate('2002-01-01', '2010-12-31')
    .filterBounds(study)
    .map(calculat);
// calculate     
function calculat(image) { 
           var cal = image.expression(
          'band*0.1',                //formula 
         {
           band: image.select('Gpp'),   
          });
          return ee.Image(cal.copyProperties(image)).set('system:time_start', image.get('system:time_start'));   
          }
// create the time series chart
var chart = ui.Chart.image.seriesByRegion({
  imageCollection: collection, 
  regions: study, 
  reducer: ee.Reducer.mean(),
  scale: 1000,
  seriesProperty:'label'})
  .setOptions({
    title:'GPP over time in flux station',
    vAxis:{title:'GPP'},
    lineWidth:1,
    });
// print the chart
print(chart);
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参考资料

GEE知乎专栏
GEE学习资料
提取时间序列数据

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