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Google Earth Engine Speckle Noise Reduction
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var sentinel1 = ee.ImageCollection('COPERNICUS/S1_GRD'); | |
var poly = ee.Geometry.Polygon( | |
[[[-95.83648681640625, 29.561512529746743], | |
[-95.042724609375, 29.57345707301757], | |
[-95.02899169921875, 30.099989515377835], | |
[-95.82275390625, 30.10711788709236]]]); | |
var spatialFiltered = sentinel1.filter(ee.Filter.eq('instrumentMode', 'IW')).filterBounds(poly) | |
.filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VV')) | |
.select('VV'); | |
var image = spatialFiltered.filterDate('2017-08-25', '2017-09-05').mosaic().clip(poly); | |
print (image); | |
//Extended Directional Smoothing | |
function eds(image) { | |
// Create a list of weights for a 3x3 kernel. | |
var dir1 = ee.List([[0, 0, 0], [0.5, 0, 0.5], [0, 0, 0]]); | |
var dir2 = ee.List([[0, 0.5, 0], [0, 0, 0], [0, 0.5, 0]]); | |
var dir3 = ee.List([[0, 0, 0.5], [0, 0, 0], [0.5, 0, 0]]); | |
var dir4 = ee.List([[0.5, 0, 0], [0, 0, 0], [0, 0, 0.5]]); | |
//Convolve directional kernels with the image | |
var d1 = image.convolve(ee.Kernel.fixed(3, 3, dir1, -1, -1)); | |
var d2 = image.convolve(ee.Kernel.fixed(3, 3, dir2, -1, -1)); | |
var d3 = image.convolve(ee.Kernel.fixed(3, 3, dir3, -1, -1)); | |
var d4 = image.convolve(ee.Kernel.fixed(3, 3, dir4, -1, -1)); | |
//Absolute value of the difference from convolved image with original values | |
var D1=(d1.subtract(image)).abs(); | |
var D2=(d2.subtract(image)).abs(); | |
var D3=(d3.subtract(image)).abs(); | |
var D4=(d4.subtract(image)).abs(); | |
//Pick min pixel value based on abs difference(first input) using reducers | |
var Dd=ee.ImageCollection([[D1,d1],[D2,d2],[D3,d3],[D4,d4]]); | |
var reducer =ee.Reducer.min(2); | |
//Select the second input to the reducer | |
var v = Dd.reduce(reducer).select('min1'); | |
return v; | |
} | |
function msd(denoised,original) { | |
var diff = denoised.subtract(original); | |
var sq= diff.pow(2); | |
var meanDict = sq.reduceRegion({ | |
reducer: ee.Reducer.mean(), | |
geometry: poly, | |
scale: 20 , | |
bestEffort:true | |
}); | |
return meanDict; | |
} | |
//plane smoothing to remove speckle noise | |
var smooth = ee.Image(image.focal_median(100, 'circle', 'meters')); | |
var image_spk = eds(image); | |
print (image_spk); | |
Map.centerObject(poly, 10); | |
Map.addLayer(image,{min:-30,max:30},'sentinel 1 raw'); | |
Map.addLayer(smooth,{min:-30,max:30},'sentinel 1 smooth'); | |
Map.addLayer(image_spk,{min:-30,max:30},'sentinel 1 EDS'); | |
var msd1=msd(smooth,image); | |
print (msd1); | |
var msd2=msd(image_spk,image); | |
print (msd2); |
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