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I am working on Sentinel-1 images. I have created a mosaic and want to apply functions related to band mathematics on it.

//Define the time interval
var start_date = ee.Date('2021-11-15');
var end_date = start_date.advance(5,'days');
var date_filter = ee.Filter.date(start_date, end_date);

// Filter the collection for the VV product from the descending track
var collection1 = ee.ImageCollection('COPERNICUS/S1_GRD')
    .filter(ee.Filter.eq('instrumentMode', 'IW'))
    //.filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VV'))
    .filter(ee.Filter.eq('orbitProperties_pass', 'DESCENDING'))
    .filterMetadata ('resolution_meters', 'equals', 10)
    .filter(date_filter)
    .filterBounds(roi)
    // .select(['VV','angle']);
print(collection1);
var vis_paraVV = {bands:'VV', min:-25, max:5};
var vis_paraVH = {bands:'VH', min:-25, max:5};
var vis_paraAN = {bands:'angle', min:30.3, max:46.8};
Map.centerObject(roi, 6);
Map.addLayer(collection1,vis_paraVV,'VV');
//Map.addLayer(collection1,vis_paraVH,'VH');
Map.addLayer(collection1,vis_paraAN,'Angle');

////Mosaic
var Mo_VVVH1 = collection1.select(['VV','VH']).mosaic().clip(roi);
var Mo_Angl1 = collection1.select(['Angle']).mosaic().clip(roi);
// var VH_mosaic = collection1.select(['VH']).mosaic();
// var AN_mosaic = collection1.select(['angle']).mosaic();

//////Speckel Filter boxcar
var boxcar = ee.Kernel.square({ radius: 1.5, units: 'pixels', normalize: true});

////apply filter to VV and VH
var Mo_VVVH1 = Mo_VVVH1.convolve(boxcar);

///Subtraction
function addVHminusVV(image) {
  var VHminusVV = ((image.select('VH')).subtract(image.select('VV'))).rename('Diff');
  return image.addBands(VHminusVV);
}
function addVHbyVV(image) {
  var VHbyVV = (image.select('VH')).divide(image.select('VV')).rename('Div');return image.addBands(VHbyVV);
}

If it's for image collection we can do following

var collection = collection1.map(addVHminusVV).map(addVHbyVV)

but how to do it for an image?

1 Answer 1

5
var yourVariable = addVHminusVV(yourImage)

Edit:

var doubleFunction = addVHbyVV(addVHminusVV(Mo_VVVH1))
print(doubleFunction, 'doubleFunction')

But why not put it in one function like this:

function oneFunction(image) {
  var VHminusVV = ((image.select('VH')).subtract(image.select('VV'))).rename('Diff');
  var VHbyVV = (image.select('VH')).divide(image.select('VV')).rename('Div');
  return image.addBands(VHminusVV).addBands(VHbyVV);
}

var applyIt = oneFunction(Mo_VVVH1)
print(applyIt, 'oneFunction')

https://code.earthengine.google.com/7d45d7401db386a284f954470b6b5454

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  • I want to map all functions at same time like we can do with image collection
    – Monish
    Commented Feb 11, 2022 at 10:34

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