EO Browser Layer NDVI data is different from those obtained by the FIS query

1

I see the statistic of a polygon in EO Browser, but I can’t get the same answer via FIS Request. The results and dates do not match.
What Layer is used in the EO Browser for NDVI (custom scripts)?

2

Dear Iglw4,

is there any specific reason you are using a custom script and not the default visualization layer for the NDVI? If you use that layer, the correct statistics for the NDVI will be returned. I recommend you to use the prepared NDVI layer and check if the statistic for that is what you expect.

If you want to use a custom script to calculate the FIS (within EO Browser), you will see in the result that it says “Based on the last band of the custom script”.

Capture

I assume that’s the difference you are experiencing is coming from that fact. If you want to get the correct statistics for the NDVI using a custom script, you can use the one below. It returns only 1 band (that holds the NDVI) and thus gives the correct statistic (note that here you don’t get the median/P10/P90 which is included in the default option).

function index(x, y) {
	return (x - y) / (x + y);
}

function isCloud (scl) {
  if (scl == 3) { // SC_CLOUD_SHADOW
    return false;
  } else if (scl == 9) { // SC_CLOUD_HIGH_PROBA
    return true; 
  } else if (scl == 8) { // SC_CLOUD_MEDIUM_PROBA
    return true;
  } else if (scl == 7) { // SC_CLOUD_LOW_PROBA
    return false;
  } else if (scl == 10) { // SC_THIN_CIRRUS
    return true;
  } else if (scl == 11) { // SC_SNOW_ICE
    return false;
  } else if (scl == 1) { // SC_SATURATED_DEFECTIVE
    return false;
  } else if (scl == 2) { // SC_DARK_FEATURE_SHADOW
     return false;
  }
  return false;
}

const cloud = isCloud (SCL)
const ndvi = index(B08, B04);
//return cloud ? [Number.NaN, 1] : [ndvi, 0];
return cloud ? [ndvi, 1] : [ndvi, 0];

Best,
Daniel

4

Thank you so much Daniel…
Regards