缩小图像集合的Google Earth Engine

问题描述

我正在使用CHIRPS数据集（每日降水）来导出特定时间范围内的平均，中位数，最小和最大降水。然后，我要提取点shapefile中包含的特定位置的值，并将结果保存在表中。该脚本似乎可以工作，但是输出表中只有零（0）作为4个变量的值。请参见下面的脚本

var lng = 65.64; 
var lat = 34.35;
var point = ee.Geometry.Point(lat,lng); 
//var aoi = point.buffer(100000); // Create an area (1km buffer around point)
var country = ee.FeatureCollection('USDOS/LSIB_SIMPLE/2017')
.filter(ee.Filter.eq('country_co','AF'));
var aoi = country;

Map.setCenter(lng,lat,5); // Center the map on this location,zoom level 10

var start = '2018-02-15'; // initial date of the image collection
var end = '2018-07-15'; //final date of the image collection

var p1 = ee.Geometry.Point([69.78086,34.65411])
var p2 = ee.Geometry.Point([61.82234,30.66048])
var table = ee.FeatureCollection(ee.List([ee.Feature(p1),ee.Feature(p2)]))

var AddPrMean = function(image) {
  var PrMean = image.reduce(ee.Reducer.mean()).rename('PrMean');
  return image.addBands(PrMean);
};

var AddPrMedian = function(image) {
  var PrMedian = image.reduce(ee.Reducer.median()).rename('PrMedian');
  return image.addBands(PrMedian);
};

var AddPrMin = function(image) {
  var PrMin = image.reduce(ee.Reducer.min()).rename('PrMin');
  return image.addBands(PrMin);
};

var AddPrMax = function(image) {
  var PrMax = image.reduce(ee.Reducer.max()).rename('PrMax');
  return image.addBands(PrMax);
};

var dataset = ee.ImageCollection('UCSB-CHG/CHIRPS/DAILY')
    .filterDate(start,end)
    .filterBounds(aoi)
    .map(AddPrMean)
    .map(AddPrMedian)
    .map(AddPrMin)
    .map(AddPrMax);
    
var composites = dataset.select(['PrMean','PrMedian','PrMin','PrMax']).first();   

var YieldLocations = ee.FeatureCollection(table);

var YPrec = composites.reduceRegions(YieldLocations,ee.Reducer.max(),1);

print(YPrec); ```

解决方法

我找到了一个似乎可行的解决方案，但是中位数始终为0。

var lat = 34.35;
var point = ee.Geometry.Point(lat,lng); 
//var aoi = point.buffer(100000); // Create an area (1km buffer around point)
var country = ee.FeatureCollection('USDOS/LSIB_SIMPLE/2017')
.filter(ee.Filter.eq('country_co','AF'));
var aoi = country;

Map.setCenter(lng,lat,5); // Center the map on this location,zoom level 10

var start = '2018-02-15'; // initial date of the image collection
var end = '2018-07-15'; //final date of the image collection

var p1 = ee.Geometry.Point([69.78086,34.65411])
var p2 = ee.Geometry.Point([61.82234,30.66048])
var table = ee.FeatureCollection(ee.List([ee.Feature(p1),ee.Feature(p2)]))

var dataset = ee.ImageCollection('UCSB-CHG/CHIRPS/DAILY')
    .filterDate(start,end)
    .filterBounds(aoi);
    
var PrMean = dataset.mean().rename('PrMean');

var PrMedian = dataset.median().rename('PrMedian');

var PrMin = dataset.min().rename('PrMin');

var PrMax = dataset.max().rename('PrMax');

var composites = PrMean
      .addBands(PrMedian)
      .addBands(PrMin)
      .addBands(PrMax);
  



var YieldLocations = ee.FeatureCollection(table);

var YPrec = composites.reduceRegions(YieldLocations,ee.Reducer.max(),1);

print(YPrec);```

google-earth-engine javascript raster