Saturday, 5 August 2017

google earth engine - Export raster with its min max range from GEE


I'm trying to export a raster as GeoTIFF from GEE and keep it's min max range (pixel value) so I can import the raster into ArcGIS and check it's min, max, mean and std.dev. in Symbology. My attempt so far can only manage to export the raster layer with a green color but when imported into ArcGIS all min, max, mean and std. dev. is 0. Here is the code I have tried:


var Blueskin =ee.Image('COPERNICUS/S2/20160721T223713_20160722T000334_T59GMK');

var Red=Blueskin.select('B4');
var NIR=Blueskin.select('B8');
var ndvi = NIR.subtract(Red).divide(NIR.add(Red)).rename('NDVI');
var mean = ee.Number(stats.get('NDVI_mean'));
var std = ee.Number(stats.get('NDVI_stdDev'));
//find regions (Ulva) in ndvi has value higher than mean +1SD
var maskImage = ndvi.updateMask(ndvi.gt(mean.add(std)));
Map.addLayer(maskImage, {palette: 'green'}, 'mask image');
//get Ulva region max min
var stats = maskImage.reduceRegion({

reducer: ee.Reducer.minMax(),
bestEffort: true,
});

// Display min and max
print(stats);
//it's a bit confusing here but NDVI_min =maskImage_min according to print I just don't know how to change the name
var NDVI_min = ee.Number(stats.get('NDVI_min'));
var NDVI_max = ee.Number(stats.get('NDVI_max'));
print(NDVI_min);

print(NDVI_max);
var visualization_params = {min: NDVI_min, max: NDVI_max, palette:'green'};
// Export a cloud-optimized GeoTIFF.
Export.image.toDrive({
image: maskImage.visualize(visualization_params),
description: '21072016UNDVI',
scale: 10,
region: table,
fileFormat: 'GeoTIFF',
formatOptions: {

cloudOptimized: true
}
});

The min and max I set in the visualization_params doesn't seem to work and I can't use ee.Reducer.minMax() as an argument in visualization_params..




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