Google Earth Engine – Showing Only One Type of Land Usage in Map

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I am trying to make a simple visualization in Google Earth Engine. The goal is just to filter the mangroves in the ESA WorldCover 10m v100 map.

According to the documentation there is a band called 'Map' and a 'Class Table' with numerical values corresponding to landcover. In my particular case mangroves have the value 95.

I tried the following:

var dataset = ee.ImageCollection("ESA/WorldCover/v100")
                
var visualization = {
  bands: ['Map'],
}; 

dataset = dataset.first()
                 .select('Map')
                 .eq(95)

Fine, it works, but I get a B&W layer with mangroves in white. The desired output woulld be a map (the default map) showing only the mangroves. In short: a visualization filter not a binary mask.

Best Answer

By applying .eq(95) you, as suggested, create a binary image. To avoid you have to apply a mask(). See the difference:

Map.addLayer(dataset.eq(95).clip(geometry), {}, 'binary')
Map.addLayer(dataset.mask(dataset.eq(95)).clip(geometry), {}, 'mask')

https://code.earthengine.google.com/9b6a8c5086d0ac87ac5ef18092bd8971

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[GIS] Extracting land cover type in Google Earth Engine

Here are two ways of doing this. The first is your method of masking with some simplified code. The second is using a grouped reducer:

var s1 = ee.ImageCollection("COPERNICUS/S1_GRD"),
S2 = ee.ImageCollection("COPERNICUS/S2"),
fc = ee.FeatureCollection("ft:1w_ciwxR9FKm0rzMH8oJ3MdyE-1U15PfiOFlGW5Ib"),
fc2 = ee.FeatureCollection("ft:18Xvf7jG2EI4mJMwj0oLV2u-05bAPiwJDaxSRy2ep");

var aoi = fc; 

var bands = ['B2', 'B3', 'B4', 'B8', 'B11', 'B12'];

var S2 = ee.ImageCollection('COPERNICUS/S2')
  .filterDate('2016-07-01', '2016-08-01')
  .filterBounds(aoi);

// You may want to use median here if there's overlapping imagery.
var image = S2.mosaic();

var geometry = ee.Geometry.Rectangle([36.977296602,-15.364411987,37.057018981,-15.447436229]);
Map.centerObject(geometry);

var landcover_roi = image.clip(geometry);

Map.addLayer(landcover_roi, {'bands': 'B12,B8,B4','min': 0,'max': 4000}, 'Sentinel 2A SWIR,NIT,R', 0);

var training = landcover_roi.sampleRegions(fc2, ["info"], 30);
var classifier = ee.Classifier.cart()
    .train(training, "info", image.bandNames());
var out = landcover_roi.classify(classifier);
Map.addLayer(out, {palette: [
  'ff0000',// cleared red
  'ffcc66',// cultivated
  '387242',// forest 
  '99ff33',// grass 
  'e0e0d1',// rock 
  'e0e0d1'// rock grass
], min:1, max:6});

Map.addLayer(ee.Image().paint(fc, 1, 3));
var fc = fc2;
Map.addLayer(fc2);

var names = ['cleared', 'cultivated1', 'cultivated2', 'grass', 'rock', 'rockgrass'];
var total = out.eq([1, 2, 3, 4, 5, 6]).rename(names);

var count = total.multiply(ee.Image.pixelArea());

// The grouped reducer ignores the weights.  Unweight here for comparison.
var area = count.reduceRegion(ee.Reducer.sum().unweighted(), geometry, 30);
print(area);

var stats = ee.Image.pixelArea().addBands(out).reduceRegion({
  reducer: ee.Reducer.sum().group(1), 
  geometry: geometry, 
  scale: 30,
});
print(stats);

Google Earth Engine – Showing Land Cover Class Area in Charts

It's not showing the number of pixels, its showing the area in meters, since that's the units on pixelArea. Divide that image by 1,000,000 to get sqkm.

Best Answer

Related Solutions

[GIS] Extracting land cover type in Google Earth Engine

Google Earth Engine – Showing Land Cover Class Area in Charts

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