ImageCollection Overview

An ImageCollection is a stack or sequence of images. An ImageCollection can be loaded by pasting an Earth Engine asset ID into the ImageCollection constructor. You can find ImageCollection IDs in the data catalog. For example, to load the Sentinel-2 surface reflectance collection:

var sentinelCollection = ee.ImageCollection('COPERNICUS/S2_SR');

This collection contains every Sentinel-2 image in the public catalog. There are a lot. Usually you want to filter the collection as shown here or here.

In addition to loading an ImageCollection using an Earth Engine collection ID, Earth Engine has methods to create image collections. The constructor ee.ImageCollection() or the convenience method ee.ImageCollection.fromImages() create image collections from lists of images. You can also create new image collections by merging existing collections. For example:

// Create arbitrary constant images.
var constant1 = ee.Image(1);
var constant2 = ee.Image(2);

// Create a collection by giving a list to the constructor.
var collectionFromConstructor = ee.ImageCollection([constant1, constant2]);
print('collectionFromConstructor: ', collectionFromConstructor);

// Create a collection with fromImages().
var collectionFromImages = ee.ImageCollection.fromImages(
  [ee.Image(3), ee.Image(4)]);
print('collectionFromImages: ', collectionFromImages);

// Merge two collections.
var mergedCollection = collectionFromConstructor.merge(collectionFromImages);
print('mergedCollection: ', mergedCollection);

// Create a toy FeatureCollection
var features = ee.FeatureCollection(
  [ee.Feature(null, {foo: 1}), ee.Feature(null, {foo: 2})]);

// Create an ImageCollection from the FeatureCollection
// by mapping a function over the FeatureCollection.
var images = features.map(function(feature) {
  return ee.Image(ee.Number(feature.get('foo')));
});

// Print the resultant collection.
print('Image collection: ', images);

Note that in this example an ImageCollection is created by mapping a function that returns an Image over a FeatureCollection. Learn more about mapping in the Mapping over an ImageCollection section. Learn more about feature collections from the FeatureCollection section.

You can also create an ImageCollection from GeoTiffs in Cloud Storage. For example:

// All the GeoTiffs are in this folder.
var uriBase = 'gs://gcp-public-data-landsat/LC08/01/001/002/' +
    'LC08_L1GT_001002_20160817_20170322_01_T2/';

// List of URIs, one for each band.
var uris = ee.List([
  uriBase + 'LC08_L1GT_001002_20160817_20170322_01_T2_B2.TIF',
  uriBase + 'LC08_L1GT_001002_20160817_20170322_01_T2_B3.TIF',
  uriBase + 'LC08_L1GT_001002_20160817_20170322_01_T2_B4.TIF',
  uriBase + 'LC08_L1GT_001002_20160817_20170322_01_T2_B5.TIF',
]);

// Make a collection from the list of images.
var images = uris.map(ee.Image.loadGeoTIFF);
var collection = ee.ImageCollection(images);

// Get an RGB image from the collection of bands.
var rgb = collection.toBands().rename(['B2', 'B3', 'B4', 'B5']);
Map.centerObject(rgb);
Map.addLayer(rgb, {bands: ['B4', 'B3', 'B2'], min: 0, max: 20000}, 'rgb');

Learn more about loading images from Cloud GeoTiffs.