I'm using a code wrote here in Stack in the question Mosaicking a Image Collection by Date (day) in Google Earth Engine to generate mosaics of Sentinel-1 by date (day) with images that cover a region. But in the code, the new Image Collection don't have a ID for each mosaic, anything like the date of the images or the date of images interval that it uses. There is any way to do this?

My code is:

var start = ee.Date('2014-10-01');
var finish = ee.Date('2018-03-31');

var collection = ee.ImageCollection('COPERNICUS/S1_GRD')
.filterDate(start, finish)
.filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VV'))
.filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VH'))
.filter(ee.Filter.eq('instrumentMode', 'IW'))
.filterMetadata('resolution_meters', 'equals', 10)

print(collection,"Original collection");

// Difference in days between start and finish
var diff = finish.difference(start, 'day');
print(diff, "Diferenca em dias");

// Make a list of all dates
var range = ee.List.sequence(0, diff.subtract(1)).map(function(day){return start.advance(day,'day')});
print(range, "Lista de todas as datas");

// Funtion for iteraton over the range of dates
var day_mosaics = function(date, newlist) {
  // Cast
  date = ee.Date(date);
  newlist = ee.List(newlist);

  // Filter collection between date and the next day
  var filtered = collection.filterDate(date, date.advance(1,'day'));

  // get date as YEARMONTHDAY. For example, for January 8th 2010
  // would be: 20100108
  var date_formatted = ee.Number.parse(date.format('YYYYMMdd'))

  // make date band as an 32 bit unsigned integer and rename it as 'date'

  var dateband = ee.Image.constant(date_formatted).toUint32().rename('date');

  // Make the mosaic
  var image = ee.Image(filtered.mosaic());

  // Add the mosaic to a list only if the collection has images
  return ee.List(ee.Algorithms.If(filtered.size(), newlist.add(image), newlist));

// Iterate over the range to make a new list, and then cast the list to an imagecollection
var newcol = ee.ImageCollection(ee.List(range.iterate(day_mosaics, ee.List([]))));
print(newcol, "Collection with mosaic images");

Map.addLayer(newcol, {bands: 'VV', min: -20, max: -5});

Follow the link to my code: Mosaicking by date.

1 Answer 1


Use the set Image method to add an ID property to each image passed through the day_mosaics function. From your example, try this at line 40:

var image = ee.Image(filtered.mosaic())
  .set('ID', date_formatted);
  • It work, jdbcode, thank you
    – Erli Pinto
    Commented Nov 15, 2019 at 15:39

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