evalscript.js

//VERSION=3
function setup() {
  return {
    input: ["B02", "B04", "B08", "B11"],
    output: [{id: "ndvi_t1", bands: 1, sampleType: "FLOAT32"},
             {id: "ndvi_t2", bands: 1, sampleType: "FLOAT32"},
             {id: "bsi_t2", bands: 1, sampleType: "FLOAT32"},
             {id: "harvested", bands: 1, sampleType: "UINT8"}],
    mosaicking: "ORBIT"
  };
}

function preProcessScenes (collections) {
    var allowedDates = ["2020-07-12", "2020-08-06"];
    collections.scenes.orbits = collections.scenes.orbits.filter(function (orbit) {
        var orbitDateFrom = orbit.dateFrom.split("T")[0];
        return allowedDates.includes(orbitDateFrom);
    });
    return collections;
}

function evaluatePixel(samples, scenes) {
  // Compute ndvi for all dates
  var ndvi = [];
  for (i=0; i<samples.length; i++){
    ndvi.push((samples[i].B08 - samples[i].B04) / (samples[i].B08 + samples[i].B04));
  }
  
  // Compute bsi for latest date
  var bsi = ((samples[0].B11 + samples[0].B04) - (samples[0].B08 + samples[0].B02)) / ((samples[0].B11 + samples[0].B04) + (samples[0].B08 + samples[0].B02));

  // Compute harvested map
  var harvested = ((ndvi[1] - ndvi[0] > 0.25 && bsi > 0.15)) ? 1 : 0;
    
  return {
    "ndvi_t1": [ndvi[1]],
    "ndvi_t2": [ndvi[0]],
    "bsi_t2": [bsi],
    "harvested": [harvested]
  };
}