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I am mapping annual rainfall in the Eastern Sahel. I have a wide colour palette which allows me to see approx rainfall p.a. within the region of interest (not elegant, but sufficient) (Image 1). My problem is that when I try to export the map to an asset it loses the palette. (Image 2) I have also tried using visualize() but without success. Any advice?

var chirps = ee.ImageCollection("UCSB-CHG/CHIRPS/PENTAD");

// Use GAUL Administrative Boundaries dataset - Admin1 dataset with district boundaries
// Set focus on the Eastern Sahel (Sudan and Eritrea)
var gaul = ee.FeatureCollection("FAO/GAUL_SIMPLIFIED_500m/2015/level1")
var Sahel = gaul.filter(ee.Filter.inList('ADM0_NAME', ['Eritrea','Sudan']))
// Overlay the district boundaries for the state
Map.addLayer(Sahel, {color: '#000000', width: 3}, 'Admin1 Boundaries')

var filtered = chirps.filter(ee.Filter.date('2020-01-01', '2020-12-31')) 

//Find cumulative rainfall
var total = filtered.reduce(ee.Reducer.sum())
//print (total) 

// Clip the classified image to the regional boundary
var SahelRainfall = total.clip(Sahel)
Map.addLayer(SahelRainfall, {min:0, max:1000, palette: ['#ff0000','#ff5300','#ffa500','#ffd200','#ffff00','#80c000','#008000','#004080',
'#0000ff','#2600c1','#4b0082']}, 'Sahel Rainfall')

// Specify area to clip and export.
var geometry = Sahel;
Export.image.toAsset({
  image: SahelRainfall,
  description: 'imageExport',
  assetId: 'rf',
  region: Sahel,

});

Map renders as follows:

Export renders like this:

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2 Answers 2

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visualize() is the missing piece as you have noticed — it is built into Map.addLayer but not Export operations. Here is an example of using it — I simply moved the parameters from addLayer into the visualize() call. Now the export should export the same results.

var SahelRainfallVis = SahelRainfall.visualize({
  min: 0,
  max: 1000,
  palette: ['#ff0000','#ff5300','#ffa500','#ffd200','#ffff00','#80c000','#008000','#004080',
'#0000ff','#2600c1','#4b0082']
});

Map.addLayer(SahelRainfallVis, {}, 'Sahel Rainfall');

Export.image.toAsset({
  image: SahelRainfallVis,
  description: 'imageExport',
  assetId: 'rf',
  region: Sahel,
});

(However, this will not include the original data bands in the asset. You could SahelRainfallVis.addBands(SahelRainfall) to do that.)

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  • I think the issue is one of how I am using the asset which is to copy and paste into a document - this doesn't seem to work. However, if I export to Drive, then it renders correctly.
    – Richard Cross
    Commented Jan 4, 2023 at 22:07
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In case you are wanting to preserve both the underlying data in the precipitation_sum band and also add your color map.

code link: https://code.earthengine.google.com/7f54e91193ff790274b8b86cade147c5

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  • Thanks @kwgeo. Unfortunately, when I run it, both exported images still look like image 2 from my OP. They don't have the map-rendered palette. Does the script work for you?
    – Richard Cross
    Commented Jan 3, 2023 at 21:01
  • Are you importing the images back into the script? For the exported image with the visualization bands added to them, you can then do Map.addLayer(image,{bands:['vis-red','vis-green','vis-blue']},'Exported image'), which is demonstrated at the bottom inside my code link. What @KevinReid explains about using addBands() is included in my code link.
    – kwgeo
    Commented Jan 4, 2023 at 17:15

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