Google Earth Engine – Downloading Pixels for “1 < BurnDate < 366" from MODIS Burned Area

downloadgoogle-earth-enginegoogle-earth-engine-javascript-apimodis

The following code downloads 3 band burned area rasters for each month in the defined range.

I am only interested in the pixels in the 'BurnDate' band, which have values between 1 and 366.

I wish to download all pixels in the defined range, which meet these conditions, as a single raster. This could be reclassified so that 1 = within range, 0 = nodata.

    var batch = require('users/fitoprincipe/geetools:batch')
    
    var dataset = ee.ImageCollection('MODIS/006/MCD64A1')
                      .filter(ee.Filter.date('2000-01-01', '2001-01-01'))
                      .select(['BurnDate']);
    // Select "1 < BurnDate < 366" here
 
    
    batch.Download.ImageCollection.toDrive(dataset, '1899', 
          {region: geometry, // use a polygon
           scale: 500,
           fileFormat: 'GeoTIFF',
           crs: 'EPSG:4326'
          })

Best Answer

You can use ee.ImageCollection.toBands() to convert each image in an image collection to a band in a multiband image. Then just export that single multiband image.

burnedArea = burnedArea.toBands();
Export.image.toDrive({
  image: burnedArea ,
  description: 'BurnedImage_multiband',
  folder: 'FOLDER',
  region: geometry,
  scale: 500,
  fileFormat: 'GeoTIFF',
  crs: 'EPSG:4326'
});

Related Solutions

[GIS] Not able to bulk download MODIS images

Here is a quick workaround using the MODIS package:

# install.packages("MODIS")
library(MODIS)

MODISoptions(localArcPath = "/path/to/modis/files", 
             outDirPath = "/path/to/modis/files/processed")

runGdal("MOD13Q1", collection = "006", # see getCollection("MOD13Q1", forceCheck = TRUE)
        tileH = 25, tileV = 6, # MODIS tile id
        begin = "2000.02.18", end = "2000.03.31", # time period
        SDSstring = "110000000000") # SDS layers to extract (here: NDVI, EVI)

If you don't want to extract certain SDS layers, but deal with the raw .hdf files instead, simply use getHdf instead of runGdal and drop 'SDSstring'.

Google Earth Engine – Calculating Annual Burned Area Using MODIS/006/MCD64A1

You were really close to obtaining the total burned area by year. You just need to move the part for calculating the burned area inside the map, so this process is done for every year. Afterwards, to return the total burned area by year, you should add that value as a property to a ee.Feature without a geometry. Finally, you can export the byYear object (which is a ee.FeatureCollection) as a CSV file with Export.table.toDrive.

var startDate = ee.Date('2010-01-01'); // set start time for analysis
var endDate = ee.Date('2021-01-01'); // set end time for analysis

// calculate the number of years to process, subtract 1 to use 2010 - 2020
var nYears = ee.Number(endDate.difference(startDate,'year')).round().subtract(1);
print(nYears)

var projection = 'EPSG:32620'

var sst =  ee.ImageCollection("MODIS/006/MCD64A1")
            .select('BurnDate')
            .filterDate(startDate, endDate)
            
print('sst',sst);
var byYear = ee.FeatureCollection(
  // map over each year
  ee.List.sequence(0,nYears).map(function (n) {
    // calculate the offset from startDate
    var ini = startDate.advance(n,'year');
    // advance just one month
    var end = ini.advance(1,'year');
    // filter collection to stay with images from ini year
    var resul = sst.filterDate(ini,end);
    // Reduce the collectino using the max reducer
    resul = resul.max()
                 .set('system:time_start', ini);
    // Get image where BurnDate was not 0 and use it as mask 
    // to apply it the Image containing the area by pixel
    resul = ee.Image.pixelArea()
                    .divide(10000)
                    .updateMask(resul.neq(0));
    // Reduce the image by summing all the pixels that are not
    // masked 
    resul = resul.reduceRegion({
      reducer: ee.Reducer.sum(), 
      geometry:roi, 
      scale: 500, 
      crs: projection, 
      maxPixels: 1e12, 
      tileScale: 4
    });
    // Export the area inside a Feature without geometry
    return ee.Feature(null, {'area_ha': resul});
}));

print('Area_ha Burned by year', byYear);

Best Answer

Related Solutions

[GIS] Not able to bulk download MODIS images

Google Earth Engine – Calculating Annual Burned Area Using MODIS/006/MCD64A1

Related Question