Google Earth Engine Masking – How to Replace Masked Pixels by Another Image

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How can I replace masked pixels with another image?

I have two sets of images: Image_A and Image_B, each has 10 bands.

I want to change the masked pixels in Image_A by the corresponding (same band, line, and column) values from Image_B.

Image_A_Update = Image_A.updateMask(Image_A.unmask(Image_B))

If Image_B also has a mask for some pixels, the output would be the mask for those pixels.

Best Answer

var Image_A_Update = Image_B.blend(Image_A);

This will be unmasked wherever at least one of the images is unmasked, using pixels from Image_A if available and pixels from Image_B otherwise.

(This is the same operation as ImageCollection.mosaic(), just applied to two images instead of an entire collection.)

Related Solutions

Google Earth Engine Masking – Setting Masked Pixel Value in Image Export

Wasn't able to get this to work with an NA output, but based on this answer I settled on this solution, which can be used to set "masked" pixel values to whatever value is set in the unmask() function:

var ndvi_final = ndvi_img.unmask(-9999).clip(ROI);
Export.image.toDrive({
  image: ndvi_final,
  description: 'MOD13Q1_comp_NDVI',
  scale: 250,
  region: ROI,
  fileFormat: 'GeoTIFF',
  formatOptions: {
    cloudOptimized: true
  }
});

Google Earth Engine – Masking Pixels in Image Collection Based on Band

You're adding the complete collection to the map. If there is any unmasked image, that pixel will be used. Since your collection contains every single Sentinel 2 image, there's a pretty good chance there some pixel where SCL isn't 1 or 11.

To verify if you're properly masking the images, just look at a single image in the collection, the first one for instance:

Map.addLayer(masked_scl.select(['B12']).first(), {palette: ['white', 'green']}, 'masked');

As far as I can see, your mask is applied to all bands.

Best Answer

Related Solutions

Google Earth Engine Masking – Setting Masked Pixel Value in Image Export

Google Earth Engine – Masking Pixels in Image Collection Based on Band

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