Statistics of Image Regions

To get image statistics in multiple regions stored in a FeatureCollection, you can use image.reduceRegions() to reduce multiple regions at once. The input to reduceRegions() is an Image and a FeatureCollection. The output is another FeatureCollection with the reduceRegions() output set as properties on each Feature. In this example, means of the Landsat 7 annual composite bands in each feature geometry will be added as properties to the input features:

// Load input imagery: Landsat 7 5-year composite.
var image = ee.Image('LE7_TOA_5YEAR/2008_2012');

// Load a FeatureCollection of counties in Maine.
var maineCounties = ee.FeatureCollection('ft:1S4EB6319wWW2sWQDPhDvmSBIVrD3iEmCLYB7nMM')
  .filter(ee.Filter.eq('StateName', 'Maine'));

// Add reducer output to the Features in the collection.
var maineMeansFeatures = image.reduceRegions({
  collection: maineCounties,
  reducer: ee.Reducer.mean(),
  scale: 30,

// Print the first feature, to illustrate the result.

Observe that new properties, keyed by band name, have been added to the FeatureCollection to store the mean of the composite in each Feature geometry. As a result, the output of the print statement should look something like:

Feature (Polygon, 7 properties)
  type: Feature
  geometry: Polygon, 34 vertices
  properties: Object (7 properties)
    B1: 23.92059069406908
    B2: 20.25958529338255
    B3: 13.907316351056284
    B4: 70.03141655348698
    B5: 34.66775258336134
    B6_VCID_2: 190.2679106547084
    B7: 13.95053603828997

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