Sentinel-2 Global Mosaic best pixel selection script
//VERSION=3 (auto-converted from 2)
//NOTE: This Custom script requires Sentinel Hub API v.2 to operate properly. It is however possible to use some parts of it already now.
function setup() {
return {
input: [{
bands: [
"B01",
"B02",
"B03",
"B04",
"B05",
"B06",
"B07",
"B08",
"B8A",
"B11",
"B12",
"AOT",
"CLD",
"SNW",
"SCL",
"viewZenithMean",
"viewAzimuthMean",
"sunZenithAngles",
"sunAzimuthAngles"
]
}],
output: [
{
id: "quality_aot",
sampleType: "UINT16",
bands: 1
},
{
id: "B11",
sampleType: "UINT16",
bands: 1
},
{
id: "B01",
sampleType: "UINT16",
bands: 1
},
{
id: "B12",
sampleType: "UINT16",
bands: 1
},
{
id: "quality_cloud_confidence",
sampleType: "UINT8",
bands: 1
},
{
id: "B02",
sampleType: "UINT16",
bands: 1
},
{
id: "valid_obs",
sampleType: "UINT8",
bands: 1
},
{
id: "B03",
sampleType: "UINT16",
bands: 1
},
{
id: "B04",
sampleType: "UINT16",
bands: 1
},
{
id: "B05",
sampleType: "UINT16",
bands: 1
},
{
id: "B06",
sampleType: "UINT16",
bands: 1
},
{
id: "B07",
sampleType: "UINT16",
bands: 1
},
{
id: "view_azimuth_mean",
sampleType: "UINT16",
bands: 1
},
{
id: "B08",
sampleType: "UINT16",
bands: 1
},
{
id: "sun_zenith",
sampleType: "UINT16",
bands: 1
},
{
id: "B8A",
sampleType: "UINT16",
bands: 1
},
{
id: "source_index",
sampleType: "INT16",
bands: 1
},
{
id: "view_zenith_mean",
sampleType: "UINT16",
bands: 1
},
{
id: "sun_azimuth",
sampleType: "UINT16",
bands: 1
},
{
id: "quality_snow_confidence",
sampleType: "UINT8",
bands: 1
},
{
id: "medoid_mos",
sampleType: "UINT16",
bands: 1
},
{
id: "quality_scene_classification",
sampleType: "UINT8",
bands: 1
}
],
mosaicking: "TILE"
}
}
function evaluatePixel(samples, scenes) {
var filteredSamples = filterByOrbitId(samples, scenes);
var best = selectRepresentativeSample(filteredSamples);
if (best === undefined) {
return {
B01: [0], B02: [0], B03: [0],
B04: [0], B05: [0], B06: [0],
B07: [0], B08: [0], B8A: [0],
B11: [0], B12: [0],
source_index: [65535],
quality_aot: [0],
quality_cloud_confidence: [0],
quality_snow_confidence: [0],
quality_scene_classification: [0],
view_zenith_mean: [32768],
view_azimuth_mean: [32768],
sun_zenith: [32768],
sun_azimuth: [32768],
medoid_mos: [65535],
valid_obs: [0]
};
} else {
var bestSample = best.sample;
var mos;
var sampleIndex = samples.indexOf(bestSample);
if (isNaN(best.mos)) {
mos = 65535;
} else {
mos = best.mos * 10000;
}
return {
B01: [bestSample.B01 * 10000],
B02: [bestSample.B02 * 10000],
B03: [bestSample.B03 * 10000],
B04: [bestSample.B04 * 10000],
B05: [bestSample.B05 * 10000],
B06: [bestSample.B06 * 10000],
B07: [bestSample.B07 * 10000],
B08: [bestSample.B08 * 10000],
B8A: [bestSample.B8A * 10000],
B11: [bestSample.B11 * 10000],
B12: [bestSample.B12 * 10000],
source_index: [sampleIndex],
quality_aot: [bestSample.AOT * 10000],
quality_cloud_confidence: [bestSample.CLD],
quality_snow_confidence: [bestSample.SNW],
quality_scene_classification: [bestSample.SCL],
view_zenith_mean: [bestSample.viewZenithMean * 100],
view_azimuth_mean: [bestSample.viewAzimuthMean * 100],
sun_zenith: [bestSample.sunZenithAngles * 100],
sun_azimuth: [bestSample.sunAzimuthAngles * 100],
medoid_mos: [mos],
valid_obs: [best.valid_obs]
};
}
}
// Utils
function toUInt16(value) {
return Math.max(0, Math.min(value * 10000, 65535));
}
function filterByOrbitId(samples, scenes) {
var orbitId = -1;
return samples
.map(function (sample, i){
return {s: sample, orbitId: scenes[i].orbitId, tileId: scenes[i].tileId};
})
.filter(e => e.s.SCL > 0)
.sort(function(a, b) {
if (a.orbitId < b.orbitId) return 1;
if (a.orbitId > b.orbitId) return -1;
if (a.tileId < b.tileId) return 1;
if (a.tileId > b.tileId) return -1;
return 0;
})
.filter(function(e) {
if (e.orbitId !== orbitId) {
orbitId = e.orbitId;
return true;
} else {
return false;
}
})
.map(e => e.s);
}
// Mosaic
const minSamplesForMedoid = 4;
function selectRepresentativeSample(samples) {
var n = samples.length;
var validSamples = samples.filter(validate);
var validSamplesNum = validSamples.length;
if (validSamplesNum == 0) {
return undefined;
}
if (validSamplesNum == 1) {
return {sample: validSamples[0], mos: NaN, valid_obs: 1};
}
if (validSamplesNum >= minSamplesForMedoid) {
return performMedoid(validSamples);
} else {
return performStc(validSamples);
}
}
function performMedoid(samples) {
var medoid = computeMedoidIndex(samples);
return {sample: samples[medoid.index], mos: medoid.spread, valid_obs: samples.length};
}
function performStc(samples) {
var bestSample = samples[0];
for (var i = 1; i < samples.length; i++) {
bestSample = computeStc(samples[i], bestSample);
}
return {sample: bestSample, mos: NaN, valid_obs: samples.length};
}
// Validate
function validate(sample) {
return validateSCL(sample.SCL) && validateViewZenithMean(sample.viewZenithMean);
}
function validateSCL(scl) {
return scl == 2 || scl == 4 || scl == 5 || scl == 6 || scl == 11;
}
function validateViewZenithMean(vzm) {
return vzm < 11;
}
function validateSamples(samples) {
return samples.every(validateSample);
}
function validateSample(sample) {
return !isNaN(sample) && isFinite(sample);
}
// STC
function computeNdvi(sample) {
return (sample.B08 - sample.B04) / (sample.B08 + sample.B04);
}
function computeVisualBandsSum(sample) {
return sample.B02 + sample.B03 + sample.B04;
}
function computeSWIRMean(sample) {
return (sample.B11 + sample.B12) / 2;
}
function computeNdwi(sample) {
return (sample.B03 - sample.B08) / (sample.B03 + sample.B08);
}
function computeStc(sampleA, sampleB) {
var keySwitch = sampleA.SCL * 100 + sampleB.SCL;
switch (keySwitch) {
//Vegetation
case 404:
var ndviSampleA = computeNdvi(sampleA);
var ndviSampleB = computeNdvi(sampleB);
if (ndviSampleA > ndviSampleB && sampleA.CLD <= sampleB.CLD) {
return sampleA;
} else {
if (ndviSampleA < ndviSampleB && sampleA.CLD <= sampleB.CLD) {
return sampleA;
} else {
return sampleB;
}
}
break;
case 405:
case 504:
if (computeVisualBandsSum(sampleA) < computeVisualBandsSum(sampleB) && sampleA.CLD <= sampleB.CLD) {
return sampleA;
} else {
return sampleB;
}
break;
case 400:
case 401:
case 402:
case 403:
case 406:
case 407:
case 408:
case 409:
case 410:
case 411:
return sampleA;
break;
case 4:
case 104:
case 204:
case 304:
case 604:
case 704:
case 804:
case 904:
case 1004:
case 1104:
return sampleB;
break;
//BARE_SOIL_DESERT
case 505:
if (computeVisualBandsSum(sampleA) < computeVisualBandsSum(sampleB) && sampleA.CLD <= sampleB.CLD) {
return sampleA;
} else {
return sampleB;
}
break;
case 500:
case 501:
case 502:
case 503:
case 506:
case 507:
case 508:
case 509:
case 510:
case 511:
return sampleA;
break;
case 5:
case 105:
case 205:
case 305:
case 605:
case 705:
case 805:
case 905:
case 1005:
case 1105:
return sampleB;
break;
//SNOW_ICE
case 1111:
if (computeVisualBandsSum(sampleA) > computeVisualBandsSum(sampleB) && sampleA.CLD <= sampleB.CLD) {
return sampleA;
} else {
return sampleB;
}
break;
case 1100:
case 1101:
case 1102:
case 1103:
case 1106:
case 1107:
case 1108:
case 1109:
case 1110:
return sampleA;
break;
case 11:
case 111:
case 211:
case 311:
case 611:
case 711:
case 811:
case 911:
case 1011:
return sampleB;
break;
//Water
case 606:
if ((computeNdwi(sampleA) > computeNdwi(sampleB) || computeSWIRMean(sampleA) < computeSWIRMean(sampleB)) &&
sampleA.CLD <= sampleB.CLD) {
return sampleA;
} else {
return sampleB;
}
break;
case 600:
case 601:
case 602:
case 603:
case 607:
case 608:
case 609:
case 610:
return sampleA;
break;
case 6:
case 106:
case 206:
case 306:
case 706:
case 806:
case 906:
case 1006:
return sampleB;
break;
//DARK_FEATURE_SHADOW
case 202:
if (computeVisualBandsSum(sampleA) > computeVisualBandsSum(sampleB) && sampleA.CLD <= sampleB.CLD) {
return sampleA;
} else {
return sampleB;
}
break;
case 200:
case 201:
case 203:
case 207:
case 208:
case 209:
case 210:
return sampleA;
break;
case 2:
case 102:
case 302:
case 702:
case 802:
case 902:
case 1002:
return sampleB;
break;
//CLOUD_SHADOW
case 303:
if (computeVisualBandsSum(sampleA) > computeVisualBandsSum(sampleB) && sampleA.CLD <= sampleB.CLD) {
return sampleA;
} else {
return sampleB;
}
break;
case 300:
case 301:
case 307:
case 308:
case 309:
case 310:
return sampleA;
break;
case 3:
case 103:
case 703:
case 803:
case 903:
case 1003:
return sampleB;
break;
//CLOUD_LOW_PROBA
case 707:
if (computeVisualBandsSum(sampleA) < computeVisualBandsSum(sampleB)) {
return sampleA;
} else {
return sampleB;
}
break;
case 700:
case 701:
case 708:
case 709:
case 710:
return sampleA;
break;
case 7:
case 107:
case 807:
case 907:
case 1007:
return sampleB;
break;
//THIN_CIRRUS
case 1010:
if (computeVisualBandsSum(sampleA) < computeVisualBandsSum(sampleB)) {
return sampleA;
} else {
return sampleB;
}
break;
case 1000:
case 1001:
case 1008:
case 1009:
return sampleA;
break;
case 10:
case 110:
case 810:
case 910:
return sampleB;
break;
//CLOUD_MEDIUM_PROBA
case 808:
if (computeVisualBandsSum(sampleA) < computeVisualBandsSum(sampleB)) {
return sampleA;
} else {
return sampleB;
}
break;
case 800:
case 801:
case 809:
return sampleA;
break;
case 8:
case 108:
case 908:
return sampleB;
break;
//CLOUD_HIGH_PROBA
case 909:
if (computeVisualBandsSum(sampleA) < computeVisualBandsSum(sampleB)) {
return sampleA;
} else {
return sampleB;
}
break;
case 900:
case 901:
return sampleA;
break;
case 9:
case 109:
return sampleB;
break;
//SATURATED_DEFECTIVE
case 101:
if (computeVisualBandsSum(sampleA) < computeVisualBandsSum(sampleB)) {
return sampleA;
} else {
return sampleB;
}
break;
case 100:
return sampleA;
break;
case 1:
return sampleB;
break;
default:
return undefined;
}
}
// Medoid
function distance(a, b) {
var ret = 0;
ret += Math.pow(a.B02-b.B02, 2);
ret += Math.pow(a.B03-b.B03, 2);
ret += Math.pow(a.B04-b.B04, 2);
ret += Math.pow(a.B06-b.B06, 2);
ret += Math.pow(a.B08-b.B08, 2);
ret += Math.pow(a.B11-b.B11, 2);
ret += Math.pow(a.B12-b.B12, 2);
return Math.sqrt(ret);
}
function computeMedoidIndex(samples) {
var n = samples.length;
var d = createDistanceMatrix(samples);
var distanceRow;
var distanceSum;
var distanceSumMin = Number.POSITIVE_INFINITY;
var medoidIndex = -1;
for (var j = 0; j < n; j++) {
distanceRow = d[j];
distanceSum = 0.0;
for (var i = 0; i < n; i++) {
distanceSum += distanceRow[i];
}
if (distanceSum < distanceSumMin) {
distanceSumMin = distanceSum;
medoidIndex = j;
}
}
return {index: medoidIndex, spread: distanceSumMin / n};
}
function createDistanceMatrix(samples) {
var n = samples.length;
var d = createArray(n, n);
for (var i = 0; i < n; i++) {
var a = samples[i];
for (var j = i + 1; j < n; j++) {
var b = samples[j]
d[i][j] = d[j][i] = distance(a, b);
}
d[i][i] = 0;
}
return d;
}
function createArray(length) {
var arr = new Array(length || 0),
i = length;
if (arguments.length > 1) {
var args = Array.prototype.slice.call(arguments, 1);
while(i--) arr[length-1 - i] = createArray.apply(this, args);
}
return arr;
}General description
Sentinel-2 Global Mosaic script is used within S2GM project to select best pixel within the chosen temporal period (10-daily, monthly, quarterly, annual).
Script requires Sentinel Hub API v.2 to run as a whole due to multi-part result. Parts of it can however be used at this point already.