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I have produced NDVI plots in GEE. I plot them with the simple Map.addLayer function, but I am for now only interested in all the pixels with values larger than 0. I would like to remove all the pixels less than 0 when I am mapping.

How do I do that?

// Define a point of interest. Use the UI Drawing Tools to import a point
// geometry and name it "point" or set the point coordinates with the
// ee.Geometry.Point() function as demonstrated here.
var point = ee.Geometry.Point([-122.292, 37.9018]);

// Import the Landsat 8 TOA image collection.
var l8 = ee.ImageCollection('LANDSAT/LC08/C01/T1_TOA');

// Get the least cloudy image in 2015.
var image = ee.Image(
  l8.filterBounds(point)
    .filterDate('2015-01-01', '2015-12-31')
    .sort('CLOUD_COVER')
    .first()
);

// Compute the Normalized Difference Vegetation Index (NDVI).
var nir = image.select('B5');
var red = image.select('B4');
var ndvi = nir.subtract(red).divide(nir.add(red)).rename('NDVI');

// Display the result.
Map.centerObject(image, 9);
var ndviParams = {min: -1, max: 1, palette: ['blue', 'white', 'green']};
Map.addLayer(ndvi, ndviParams, 'NDVI image');

I thought I could do something like:

var value = 0
var mask = ndvi.lt(0)

// create new image
var new_image = mask.multiply(value).add(ndvi.multiply(mask.not()))

but that just sets it to be 0 and still plots it.

1 Answer 1

1

It ended up being simple:

var maskNDVI = ndvi.gt(0); //set the threshold you need. Here I keep all pixels greater than 0.
var maskedNDVI = ndvi.updateMask(maskNDVI); //Apply this in a mask

Map.addLayer(maskedNDVI,{min: 0, max: 1, palette: palette}, 'NDVI');

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