Google Earth Engine – How to Concatenate Export File Name

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I am exporting an image from google earth engine and I want the export file name to be a string I created and concatenate the image metaData (date) with it.

var date = image.get('system:index');
var file_name = ee.String('Area').cat(date);

Export.image.toDrive({
        image: B11,
        description: file_name,
        region: study_area,
        scale: 30,
        maxPixels: 1e8
    });

But in the export tab the file name changes to something like this

ee.String({ "type": "Invocation", "arguments": { "string1": "1495_B4", "string2": { "type": "Invocation", "arguments": { "input": { "type": "Invocation", "arguments": { "object": { "type": "Invocation", "arguments": { "collection": { "type": "Invocation", "arguments": { "collection": { "type": "Invocation", "arguments": { "collection": { "type": "Invocation", "arguments": { "collection": { "type": "Invocation", "arguments": { "collection": { "type": "Invocation", "arguments": { "id": "COPERNICUS/S2_SR_HARMONIZED" }, "functionName": "ImageCollection.load" }, "filter": { "type": "Invocation", "arguments": { "leftField": ".all", "rightValue": { "type": "Invocation", "arguments": { "geometry": { "type": "Invocation", "arguments": { "collection": { "type": "Invocation", "arguments": { "tableId": "users/muddasir_assets_workshop/1461" }, "functionName": "Collection.loadTable" } }, "functionName": "Collection.geometry" } }, "functionName": "Feature" } }, "functionName": "Filter.intersects" } }, "functionName": "Collection.filter" }, "filter": { "type": "Invocation", "arguments": { "rightField": "system:time_start", "leftValue": { "type": "Invocation", "arguments": { "start": "2022-07-14", "end": "2022-08-11" }, "functionName": "DateRange" } }, "functionName": "Filter.dateRangeContains" } }, "functionName": "Collection.filter" }, "filter": { "type": "Invocation", "arguments": { "leftField": "CLOUDY_PIXEL_PERCENTAGE", "rightValue": 10 }, "functionName": "Filter.lessThan" } }, "functionName": "Collection.filter" }, "baseAlgorithm": { "type": "Function", "argumentNames": [ "_MAPPING_VAR_0_0" ], "body": { "type": "Invocation", "arguments": { "input": { "type": "ArgumentRef", "value": "_MAPPING_VAR_0_0" }, "bandSelectors": [ "B3", "B4", "B5", "B8", "B11" ] }, "functionName": "Image.select" } } }, "functionName": "Collection.map" } }, "functionName": "Collection.first" }, "property": "system:index" }, "functionName": "Element.get" } }, "functionName": "String" } }, "functionName": "String.cat"})

Best Answer

This is a classic issue of working with client and server side objects. The problem here is that Export.image.toDrive expects a client side string in the description of the image; however, you are providing a server side string (ee.String). An easy way to convert it to a client side string is using getInfo(). This should do the trick.

Export.image.toDrive({
        image: B11,
        description: file_name.getInfo(),
        region: study_area,
        scale: 30,
        maxPixels: 1e8
    });

Related Solutions

Export Images in Google Earth Engine with Date Name – Instructions

From the official Documentation:

Export.image.toDrive(image, description, folder, fileNamePrefix, dimensions, region, scale, crs, crsTransform, maxPixels, shardSize, fileDimensions, skipEmptyTiles)

Creates a batch task to export an Image as a raster to Drive. Tasks can be started from the Tasks tab. "crsTransform", "scale", and "dimensions" are mutually exclusive.

Arguments: image (Image): The image to export.

description (String, optional): A human-readable name of the task. Defaults to "myExportImageTask".

folder (String, optional): The Google Drive Folder that the export will reside in.

fileNamePrefix (String, optional): The Google Drive filename for the export. Defaults to the description.*

What you want is fileNamePrefix. So:

// Load a FeatureCollection 
var violada = ee.FeatureCollection("ft:1KmH70D7VKdiWocelf0RtbL_kQhGk0LGkQQ7O-ceG");

// Load a FeatureCollection Sentinel 2.
var s2 = ee.ImageCollection('COPERNICUS/S2')
          .filterBounds(violada)
          .filterDate('2016-10-01', '2017-09-30');
print(s2);

// Function to mask clouds using the Sentinel-2 QA band..
function maskS2clouds(image) {
  // get date of the image to pass it through
  var date = image.date().millis()
  var qa = image.select('QA60');

  // Bits 10 and 11 are clouds and cirrus, respectively.
  var cloudBitMask = ee.Number(2).pow(10).int();
  var cirrusBitMask = ee.Number(2).pow(11).int();

  // Both flags should be set to zero, indicating clear conditions.
  var mask = qa.bitwiseAnd(cloudBitMask).eq(0).and(
             qa.bitwiseAnd(cirrusBitMask).eq(0));

  // Return the masked and scaled data.
  return image.updateMask(mask).divide(10000).set('system:time_start', date);
}
var imagen=s2.map(maskS2clouds);

print(ee.Image(imagen.first()))

// visualize the first image in the collection, pre- and post- mask
var visParams = {bands: ['B8','B4','B3']}
Map.addLayer(ee.Image(imagen.first()), visParams, 'clouds masked', false)
Map.addLayer(ee.Image(s2.first()), visParams, 'original', false)

//add ndwi
var addNDVI = function(image) {
  return image.addBands(image.normalizedDifference(['B8','B4']).rename('NDVI'));
};
var imagen2=imagen.map(addNDVI);

var NDVI = imagen2//.select(['NDVI']);
print(ee.Image(NDVI.first()));

var composite = NDVI.qualityMosaic('NDVI').clip(violada);
print(composite);

// Visualize NDVI
var ndviPalette = ['FFFFFF', 'CE7E45', 'DF923D', 'F1B555', 'FCD163', '99B718',
  '74A901', '66A000', '529400', '3E8601', '207401', '056201',
  '004C00', '023B01', '012E01', '011D01', '011301'];
Map.addLayer(composite.select('NDVI'),
            {min:0, max: 1, palette: ndviPalette}, 'ndvi');
            

//List NDVI
var list=NDVI.toList(150);
    for (var i=0;i<150;i++){
         var image=ee.Image(list.get(i));
         var date = image.date().format('yyyy-MM-dd').getInfo()
         var name= 'NDVI_'+i.toString()+'_'+date
         print(name);
    // Export NDVI        
         Export.image.toDrive({ 
               image: image,
               description: name,
               fileNamePrefix: name,
               scale: 10,
               region:violada,
               crs : 'EPSG:32630'
               });
    }
Map.setCenter(-0.6, 42, 12);

Google Earth Engine Error – Image Select Pattern Did Not Match Any Bands

The problem was that the max reducer renames the bandname to "max" It had to be renamed again.

trainingMap = ee.FeatureCollection('users/xxx/xxx')
trainingMapReduced = trainingMap.reduceToImage([RESPONSE], 'max')
trainingMapReduced = trainingMapReduced.rename(RESPONSE)

Best Answer

Related Solutions

Export Images in Google Earth Engine with Date Name – Instructions

Google Earth Engine Error – Image Select Pattern Did Not Match Any Bands

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