I'm exporting a Landsat RGB image from Earth Engine. I want to use the full native resolution (30-m pixels) in the output file. However, it seems that using 30 in the scale argument fails to export at full resolution. I tried exporting the same data using a scale argument of 2 with considerable increase in resolution (as well as filesize). Looking at the images across the same region indicates that this isn't an artificial increase in resolution; there is a real increase in image quality. Can anyone explain what's going on here?

Google Earth Engine code:

var cali = ee.FeatureCollection("TIGER/2016/Counties")
  .filter(ee.Filter.eq('NAME','San Luis Obispo'));

// Load a raw Landsat scene and display it.
var raw = ee.ImageCollection('LANDSAT/LC08/C01/T1')

// Reduce image collection to median pixel value
var raw_median = raw.median();
var imageRGB = raw_median.visualize({bands: ['B4', 'B3', 'B2'], min: 6000, max: 20000});

// Export imagery
  image: imageRGB.clip(cali),
  description: 'SLO_LS8_RGB_30',
  scale: 30,
  region: cali.geometry().bounds(),
  maxPixels: 1e13});

  image: imageRGB.clip(cali),
  description: 'SLO_LS8_RGB_2',
  scale: 2,
  region: cali.geometry().bounds(),
  maxPixels: 1e13});

Then loading the data into R (I just used the first file from the 2-"meter" data for a quick comparison):

raster.30 = stack("SLO_LS8_RGB_30.tif")

raster.2a = stack("SLO_LS8_RGB_2-0000000000-0000000000.tif")

plotRGB(raster.30, add=T)


The two images look like this:

Scale = 30 Scale = 30 image

Scale = 2 Scale = 2 image


Ok, it looks like the issue here is not on the Earth Engine end. Exporting at Scale = 2 does "increase" the resolution but I think it's an artifact of the resampling process. The real issue lies in the maxpixels argument of R's plotRGB; resetting that to a higher value improves plotting resolution.

plotRGB(raster.30, maxpixels = 100000000)

Edit: To address the actual question above, the scale does correspond to resolution of the export image. So, Scale = 30 means 30-m resolution imagery.

  • 3
    you know you are allowed to accept your own answer, but from what I understood and tested, setting the scale to 30m would get you a resampled image in EPSG:4326 and not the original UTM image at native resolution. To get the original resolution, you need to export setting the crs to the correct projection. – Andrei May 22 '20 at 19:16

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