Exporting daily mosaic of Sentinel 2 data using Google Earth Engine

Question

I'm new to GEE. I have used this code to view the mosaic data. How should I export each mosaic data with unique file name (date).

var aoi = ee.FeatureCollection('users/sujithapeterraj/HAssan') 

var s2 = ee.ImageCollection('COPERNICUS/S2_SR')
  .filterBounds(aoi)
  .filterDate('2019-01-01', '2019-01-30'); // // %Y-%m-%d

print(s2.first(), 'first image s2');


// Function to mosaic by date, orbit, etc
function mosaicBy(imcol){
  // imcol: An image collection
  // returns: An image collection

  // return the collection as a list of images (not an image collection)
  var imlist = imcol.toList(imcol.size());

  // Get all the dates as list
  var all_dates = imlist.map(function(im){
    return ee.Image(im).date().format("YYYY-MM-dd");
  });

  // get all orbits as list
  var all_orbits = imlist.map(function(im){
    return ee.Image(im).get('SENSING_ORBIT_NUMBER');
  });

  // get all spacecraft names as list
  var all_spNames = imlist.map(function(im){
    return ee.Image(im).get('SPACECRAFT_NAME');
  });

  // this puts dates, orbits and names into a nested list
  var concat_all = all_dates.zip(all_orbits).zip(all_spNames);

  // here we unnest the list with flatten, and then concatenate the list elements with " "
  concat_all = concat_all.map(function(el){
    return ee.List(el).flatten().join(" ");
    });

  // here, just get distinct combintations of date, orbit and name
  var concat_unique = concat_all.distinct();

  // mosaic
  var mosaic_imlist = concat_unique.map(function(d){

    // split into components
    var d1 = ee.String(d).split(" ");

    var date1 = ee.Date(d1.get(0));
    var orbit = ee.Number.parse(d1.get(1)).toInt();
    var spName = ee.String(d1.get(2));

    var im = imcol
      .filterDate(date1, date1.advance(1, "day")) // filter with start date, and then end date, ie date + 1 day
      .filterMetadata('SPACECRAFT_NAME', 'equals', spName)
      .filterMetadata('SENSING_ORBIT_NUMBER','equals', orbit)
      .mosaic();

    return im.set(
        "system:time_start", date1.millis(),
        "system:date", date1.format("YYYY-MM-dd"),
        "system:id", d1);
  });

  return ee.ImageCollection(mosaic_imlist);
}


var s2day = mosaicBy(s2);

print(s2day);

// Make list of image to display each one
var listOfImages = s2day.toList(s2day.size());

Map.centerObject(aoi, 6); 

Map.addLayer(s2day.first(), {bands: 'B4,B3,B2', min: 300, max: 3000});

Map.addLayer(ee.Image(listOfImages.get(1)), {bands: 'B4,B3,B2', min: 300, max: 3000}); // second image
Map.addLayer(ee.Image(listOfImages.get(2)), {bands: 'B4,B3,B2', min: 300, max: 3000}); // third image
Map.addLayer(ee.Image(listOfImages.get(3)), {bands: 'B4,B3,B2', min: 300, max: 3000}); // 4th image

Answer 1

Based in the answer to this question, following code can do that.

var aoi = ee.Geometry.Polygon(
        [[[81.0312993277979, 29.97063836127144],
          [81.0312993277979, 28.91826467453208],
          [83.2505376090479, 28.91826467453208],
          [83.2505376090479, 29.97063836127144]]], null, false);

Map.centerObject(aoi);
Map.addLayer(aoi);

//////////////////////////////////////////////////
var s2 = ee.ImageCollection('COPERNICUS/S2_SR')
  .filterBounds(aoi)
  .filterDate('2019-01-01', '2019-01-30'); // // %Y-%m-%d

var scale = s2.first().select('B1').projection().nominalScale();

//print(scale);

//print(s2);

// Function to mosaic by date, orbit, etc
function mosaicBy(imcol){
  // imcol: An image collection
  // returns: An image collection

  // return the collection as a list of images (not an image collection)
  var imlist = imcol.toList(imcol.size());

  // Get all the dates as list
  var all_dates = imlist.map(function(im){
    return ee.Image(im).date().format("YYYY-MM-dd");
  });

  // get all orbits as list
  var all_orbits = imlist.map(function(im){
    return ee.Image(im).get('SENSING_ORBIT_NUMBER');
  });

  // get all spacecraft names as list
  var all_spNames = imlist.map(function(im){
    return ee.Image(im).get('SPACECRAFT_NAME');
  });

  // this puts dates, orbits and names into a nested list
  var concat_all = all_dates.zip(all_orbits).zip(all_spNames);

  // here we unnest the list with flatten, and then concatenate the list elements with " "
  concat_all = concat_all.map(function(el){
    return ee.List(el).flatten().join(" ");
    });

  // here, just get distinct combintations of date, orbit and name
  var concat_unique = concat_all.distinct();

  // mosaic
  var mosaic_imlist = concat_unique.map(function(d){

    // split into components
    var d1 = ee.String(d).split(" ");

    var date1 = ee.Date(d1.get(0));
    var orbit = ee.Number.parse(d1.get(1)).toInt();
    var spName = ee.String(d1.get(2));

    var im = imcol
      .filterDate(date1, date1.advance(1, "day")) // filter with start date, and then end date, ie date + 1 day
      .filterMetadata('SPACECRAFT_NAME', 'equals', spName)
      .filterMetadata('SENSING_ORBIT_NUMBER','equals', orbit)
      .mosaic();

    return im.set(
        "system:time_start", date1.millis(),
        "system:date", date1.format("YYYY-MM-dd"),
        "system:id", d1);
  });

  return ee.ImageCollection(mosaic_imlist);
}

var s2day = mosaicBy(s2);

print(s2day);

// Make list of image to display each one
var listOfImages = s2day.toList(s2day.size());

var dates = listOfImages.map(function(ele) {
  
  return ee.Image(ele).get('system:date');
  
});

print("dates", dates);

dates.getInfo().forEach(function (c) {
  
  var idx = dates.indexOf(c);
  
  var image = ee.Image(listOfImages.get(idx)).toInt16();

  image = image
    .clip(aoi);

  Export.image.toDrive({
      image : image,
      description: 'image'.concat('_', c),
      folder: 'GEE_Folder',
      scale: scale,
      crs : 'EPSG:4326',
      fileFormat: 'GeoTIFF',
      region: aoi
      });

   // display

  Map.addLayer(image, {}, 'image'.concat('_', c));
  
});

After running it in GEE code editor, I got result of following picture.

Into red rectangle, there were loaded 18 images corresponding to my aoi. I only run one task in Tab Tasks and it was successfully (image has 23 bands).