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I'm using GEE to visualize WorldView and Ikonos imagery. If I just use the bands for image visualization as seen below, the image appears very dark:

var vizWV = {
  bands: ['b5', 'b3', 'b2'], 
}; 

I tried adjusting min and max values, as well as the gamma (seen below), but the image appears to have a blue tint.

  var vizWV = {
  bands: ['b5', 'b3', 'b2'], 
  min: 20,
  max: 100,
  gamma: 1.8,
}; 

If I open these same images in ArcMap, they display in true color as they should with no blue tint. Does anyone have any insight into this?

1 Answer 1

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I had a similar problem with SPOT-5 Imagery being visualised differently between QGIS and GEE, so I delved more into the Image Visualisation documentation;

Each of the gain, bias, min, max and gamma arguments can take either a single value, which will be applied to all bands, or a list of values the same length as [the number of] bands.

As you can see below, on QGIS the image is stretched to the min/max values of each individual band. Red and Green peak at 0.15, but Blue peaks at 0.33: Screenshot of SPOT 5 Scene in QGIS

If you set a single Min/Max value for visualisation parameters in GEE, it either clips the Blue to 0.15, or stretches the Red and Green beyond their maximum values to 0.33: Screenshot of a Blue SPOT-5 scene in GEE Screenshot of a dark Blue SPOT-5 scene in GEE

Instead, take note of the min/max values it is stretching to on each Band on QGIS/ArcGIS, and create the list of those min/max values when setting up the visualisation parameters:

// Set it as accurately as you want, or with a 95% clip, std-dev, etc 
var SpotVis = {
  //    B1(R)  B2(G)  B3(B)
  bands: ['b1', 'b2', 'b3'],
  min: [0.011, 0.024, 0.083],
  max: [0.154, 0.144, 0.336]
};

Map.addLayer(SPOT5, SpotVis, 'SPOT 5 Test w/SPOTVis');

or set the visualisation up as you add the layer to the Map, for individual tiles:

Map.addLayer(SPOT5,{bands:['b1','b2','b3'], min: [0.011, 0.024, 0.083], max: [0.154, 0.144, 0.336]}, 'SPOT 5 Test w/o SPOTVis');

If I've setup sharing correctly, you should be able to see this example on GEE: Screenshot of accurately QGIS-displayed SPOT-5 scene in GEE

You could also apply this to correct for band-specific gain values for DN Radiances, or Gamma for band specific brightnesses in the same way.

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