66 lines
2.2 KiB
JavaScript
66 lines
2.2 KiB
JavaScript
////// Script 2: Calculate indices and apply a mask //////
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// Load an image.
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var image = ee.Image('LANDSAT/LC08/C01/T1_TOA/LC08_044034_20140318');
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// Center map view
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Map.centerObject(image,10)
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// Create an NDWI image, define visualization parameters and display.
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var ndwi = image.normalizedDifference(['B3', 'B5']);
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var ndwiViz = {min: 0.5, max: 1, palette: ['00FFFF', '0000FF']};
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Map.addLayer(ndwi, ndwiViz, 'NDWI');
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Map.addLayer(ndwi, ndwiViz, 'NDWI false', false);
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// Question 1: What's "false" doing?
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//Zeigt den Layer nicht an.
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// Mask the non-watery parts of the image, where NDWI < 0.4.
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var ndwiMasked = ndwi.updateMask(ndwi.gte(0.4));
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Map.addLayer(ndwiMasked, ndwiViz, 'NDWI masked');
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// Question 2: What does the function .gte actually do?
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//Maskiert alles wo der NDWI unter 0.4 ist.
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//// Create visualization layers.
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// The .visualize function creates images that contain the visualisation parameters.
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var imageRGB = image.visualize({bands: ['B3', 'B2', 'B1'], max: 0.5});
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var ndwiRGB = ndwiMasked.visualize({min: 0.5, max: 1, palette: ['00FFFF', '0000FF']});
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Map.addLayer(imageRGB, {}, 'imageRGB');
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Map.addLayer(ndwiRGB, {}, 'NDWI masked - 2'); //looks the same than the fist visualization, just another layer
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// Mosaic the visualization layers and display.
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var mosaic = ee.ImageCollection([imageRGB, ndwiRGB]).mosaic();
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Map.addLayer(mosaic, {}, 'mosaic');
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//Question 3: What does the mosaic function do?
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//Fügt das RGB Image und das NDWI Image zusammen.
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// Exercise 2a:
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// Calculate the NDVI and visualize it
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var ndvi = image.normalizedDifference(['B4', 'B5']);
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// Find a threshold for differentiating vegetated and non-vegetated areas
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var ndviViz = {min: -1, max: 1};
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Map.addLayer(ndvi, ndviViz, 'NDVI');
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// Create a mask that masks non-vegetated areas
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// Mask the non-planty parts of the image, where NDVI < 0.
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var ndviMasked = ndvi.updateMask(ndvi.gte(0));
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// Find a nice visualization
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var ndviRGB = ndviMasked.visualize({min: -1, max: 1, palette: ['00FFFF', '0000FF']});
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Map.addLayer(ndviRGB, {}, 'NDVI masked');
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// Create a mosaic of the Landsat image and the NDVI data.
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var mosaic = ee.ImageCollection([imageRGB, ndviRGB]).mosaic();
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Map.addLayer(mosaic, {}, 'mosaic');
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