EO Browser - Sentinel 2 indices geoTIFF Raster bands

#1

Using EO Browser I’ve downloaded the NDVI index,
why the geotiff 32bit has 3bands and not a unique band with the NDVI value of the pixels ?
Is possibile to obtain a one band raster? Or which of the 3 bands is the correct one ?

many thanks
Simone

#2

Hi Simone

You get 3 bands because NDVI layer in EO browser is a visualized layer therefore has RGB bands.

Yes it is possible to download only 1 band with actual NDVI values on EO browser.

Please refer to this thread for a detailed answer.

You need to first create your custom layer using this script below which returns 1 NDVI band

//VERSION=3
    function setup() {
      return{
        input: [{
          bands: ["B04", "B08"]
        }],
        output: {
          id: "default",
          bands: 
        }
      }
    }
    function evaluatePixel(sample) {
      let ndvi = (sample.B08 - sample.B04) / (sample.B08 + sample.B04)
      return [ ndvi ]
    }
  • instead of selecting NDVI, go to custom , then paste the script above to custom script section

image
image1494×831 432 KB

  • When you go to download your custom layer, it should be 1 band, and you can also select geotiff 32 bit.

hope that helps, otherwise feel free to ask further questions

#3

image
image500×541 16.2 KB

Thank you for your answer, but I get errors on the script.
I cannot find the error…
many thanks
Regards

#4

Hi @meteoclima,

Sorry, there was a typo in @dorothyrono’s code: it is missing the parameter that sets the output number of bands, which in this case should be 1.

If you try the following Evalscript, it should work (see example):

//VERSION=3
function setup() {
  return {
    input: ["B08", "B04"],
    output: { bands: 1 }
  };
}

function evaluatePixel(sample) {
  var ndvi = (sample.B08 - sample.B04) / (sample.B08 + sample.B04);  
  return [ndvi];
}

Note: this script in itself is designed for display purposes (scaled to the range 0-255). However, when you select Image format: TIFF (32-bit float) in the download section of EO Browser (under Analytical) the system will retrieve the raw values in Float for you.

#5

Hello,
thank you very much. Yes It works fine! great!

Best Regards
Simone