GEE:计算image区域内像素最大最小值

GEE:计算image区域内像素最大最小值

使用GEE统计指定区域内像素的最大最小值（如DEM）时，需要使用到GEE中的.regionReducer和reducer函数。

min & max

最大值：ee.Reducer.max()
最小值：ee.Reducer.min()
最大最小值：ee.Reducer.minMax()

代码实现

最大值

//给定区域
var CQ = 
    /* color: #98ff00 */
    /* shown: false */
    ee.Geometry.Polygon(
        [[[107.81231551184783, 29.581711188146137],
          [108.25176863684783, 30.49472925792531],
          [110.00958113684783, 31.173930341237376],
          [108.60333113684783, 31.922923346675326],
          [106.84551863684783, 30.418966567079185],
          [105.35137801184783, 30.418966567079185],
          [105.35137801184783, 29.428726935782418],
          [107.10919051184783, 28.89146956313381]]]);
          
//选择数据集，这里选择DEM
var DEM=ee.Image("CGIAR/SRTM90_V4");
//统计最大值
var max=DEM.reduceRegion({
    
  reducer:ee.Reducer.max(),
  geometry:CQ,
  scale:90
});  
print(max) 

输出结果：

最小值

//给定区域
var CQ = 
    /* color: #98ff00 */
    /* shown: false */
    ee.Geometry.Polygon(
        [[[107.81231551184783, 29.581711188146137],
          [108.25176863684783, 30.49472925792531],
          [110.00958113684783, 31.173930341237376],
          [108.60333113684783, 31.922923346675326],
          [106.84551863684783, 30.418966567079185],
          [105.35137801184783, 30.418966567079185],
          [105.35137801184783, 29.428726935782418],
          [107.10919051184783, 28.89146956313381]]]);
          
//选择数据集，这里选择DEM
var DEM=ee.Image("CGIAR/SRTM90_V4");
//统计最大值
var min=DEM.reduceRegion({
    
  reducer:ee.Reducer.min(),
  geometry:CQ,
  scale:90
});  
print(min) 

输出结果：

同时计算最大最小值

可以同时获取区域像素的最大最值，如下：

//给定区域
var CQ = 
    /* color: #98ff00 */
    /* shown: false */
    ee.Geometry.Polygon(
        [[[107.81231551184783, 29.581711188146137],
          [108.25176863684783, 30.49472925792531],
          [110.00958113684783, 31.173930341237376],
          [108.60333113684783, 31.922923346675326],
          [106.84551863684783, 30.418966567079185],
          [105.35137801184783, 30.418966567079185],
          [105.35137801184783, 29.428726935782418],
          [107.10919051184783, 28.89146956313381]]]);
          
//选择数据集，这里选择DEM
var DEM=ee.Image("CGIAR/SRTM90_V4");
var maxmin=DEM.reduceRegion({
    
  reducer:ee.Reducer.minMax(),
  geometry:CQ,
  scale:90
});
print(maxmin)

输出结果：