3

I have downloaded Sentinel-1 SAR images from GEE in VV and VH polarization. I have two groups of images: 17 images in VV polarization and 17 images with VH polarization.

I have a model that is suppose to correct those images in SNAP:

enter image description here

As you can see, whenever I try to run this I get this error message:

enter image description here

I thought maybe the error is because I have for each image only one polarization mode because my code extract it like this. Or maybe the problem is that I haven't downloaded it directly from Sentinel, however, I have seen many researches that have used GEE to download SAR images.

This is the code I have been using:

var img = ee.ImageCollection('COPERNICUS/S1_GRD')
        .filter(ee.Filter.listContains('transmitterReceiverPolarisation','VH'))
        .filter(ee.Filter.eq('instrumentMode', 'IW'))
        .select('VH')
        .filterDate('2018-01-01','2018-05-01')
        .filterBounds(geometry)
        .map(function(image) {
          var edge = image.lt(-30.0);
          var maskedImage = image.mask().and(edge.not());
          return image.updateMask(maskedImage);
        });

var desc = img.filter(ee.Filter.eq('orbitProperties_pass', 'DESCENDING'));

var dataset=img.size();
print(dataset)

var clippedCol=img.map(function(im){ 
   return im.clip(geometry);
}); 

var listOfImages =(clippedCol.toList(clippedCol.size()));

var listOfNumbers = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16];

for (var i in listOfNumbers) {
  var image = ee.Image(listOfImages.get(listOfNumbers[i]));
  var toexport=image.visualize({min: -30, max: 5}).addBands(image);

  // do what ever you need with image
  Map.addLayer(image,{min: -30, max: 5}, i);
  Export.image.toDrive({
  image: toexport.toFloat(),
  description: i,
  scale:10,
  crs:'EPSG:4326',
  maxPixels:1310361348,
  region:geometry.geometry().bounds()});
}

Map.centerObject(geometry)

My end goal is to be able to process my SAR images that were download from GEE.

Additional information: I am able to display those images from GEE, but can't run any analysis, and each image has 2 bands as you can see here:

enter image description here

Edit2 - I thought maybe it doesn't work because the images are corrected already. I have tried to create stack but got the next error message:

enter image description here

1

The Sentinel-1 SAR data available as GeoTIFFs from Google Earth Engine are already preprocessed and geocoded:

https://developers.google.com/earth-engine/datasets/catalog/COPERNICUS_S1_GRD

SNAP needs the original product structure and metadata to be able to apply SAR-related processing functions.

You can, however, create a stack in SNAP if you select "Product Geolocation" instead of "Orbit" in the stacking module under "Initial Offset Method".

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.