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I am trying to set up a daily water and cloud detection system and need to use a high temporal resolution. Therefore I intend on using daily MODIS imagery (MOD09GQ). In the water detection, cloud shadows interfere with the image. Question:

Is there alternative (daily) method (e.g. MODIS band combination) or image collection, which could work in combination with the 250m daily MODIS imagery to distinguish cloud shadows and surface water?

Code:

var modis = ee.ImageCollection("MODIS/006/MOD09GQ"),
aoi = /* color: #d63000 */ee.Geometry.Polygon(
    [[[1.95556640625, 6.782807298156471],
      [1.966552734375, 6.127810565018445],
      [2.757568359375, 6.127810565018445],
      [2.74658203125, 6.804625672985183]]]);

// center image on aoi
Map.setCenter(2.44720458984375,6.443588525393941, 10); // Lake Nokoue

// Select the image
var image = ee.Image(modis.filterDate('2017-12-03','2017-12-05').filterBounds(aoi).first());
print('A MODIS Scene', image);

// Retrieve the timestamp and convert it to a date
var date = ee.Date(image.get('system:time_start'));
print('TIMESTAMP MODIS: ', date);

var bands_normal_2 = {
  bands: ['sur_refl_b02'],
  min: 0,
  max: 10000
};

var bands_normal_1 = {
  bands: ['sur_refl_b01'],
  min: 0,
  max: 4000
};

var bands_clouds = {
  bands: ['sur_refl_b01'],
  min: 1000,
  max: 4000
};

var bands_water = {
  bands: ['sur_refl_b02'],
  min: 0,
  max: 1500
};

Map.addLayer(image, bands_normal_2, 'MODIS image b02');
Map.addLayer(image, bands_normal_1, 'MODIS image b01');
Map.addLayer(image, bands_clouds, 'Clouds MODIS');
Map.addLayer(image, bands_water, 'Water MODIS');

Surface water and cloud shadow cloud_mask

Normal surface reflectance image

image

  • 1
    Please only ask a single question per post. If you are unsure how to best structure your post you can take a look at the tour. – Kersten May 7 '18 at 11:09
  • Every passive sensor in visible spectrum will have troubles with clouds. Try an active sensor instead, as Sentinel-1 – aldo_tapia May 7 '18 at 11:17

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