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Gee learning notes 2

2022-07-02 13:25:00 【RS＆Hydrology】

1. example 1
（1） Load vector boundary data

// load a polygon watershed boundary (here, a public vector dataset already in GEE)
// note: see tutorial linked above for guidance on importing vector datasets
var WBD = ee.FeatureCollection("USGS/WBD/2017/HUC06");
print(WBD.limit(5));
Map.addLayer(WBD, {
    }, 'watersheds')

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(2) According to the attribute information , Select the area you want to study , If you choose name=Republican The region of interest .

// use the inspector tool to find the name of a watershed that interests you
var watershed = WBD.filterMetadata('name', 'equals', 'Republican');
print(watershed);

// set the map view and zoom level, and add watershed to map
Map.centerObject(watershed,7);
Map.addLayer(watershed, {
    }, 'watershed');

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(3) Filter image sets

//load jrc dataset
var jrccollection = ee.ImageCollection('JRC/GSW1_3/MonthlyHistory')
          .filterBounds(watershed)
          .filterDate('2017-01-01', '2017-12-31');
print(jrccollection);

(4) Use vector boundaries to crop images , Visual image

//clip function 
function clipImg(image){
    
  return image.clipToCollection(watershed);
}

var clipCol=jrccollection.map(clipImg);

var visualization = {
    
  bands: ['water'],
  min: 0.0,
  max: 2.0,
  palette: ['ffffff', 'fffcb8', '0905ff']
};

Map.centerObject(watershed, 4);

Map.addLayer(clipCol, visualization, 'Water');