Merge pull request #348 from azlinszkysinergise/main

Correction of agri growth stage quarterly mosaic custom script

Author: Guyon-Duifhuizen

sentinel-2/agriculture_growth_stage/quarterly_mosaics.js

@@ -1,14 +1,21 @@
 //VERSION=3 (auto-converted from 1)
 /*
-Source: @HarelDan - https://github.com/hareldunn/GIS_Repo/blob/master/Multi-Temporal%20NDVI%20for%20Sentinel%20Hub%20Custom%20Scripts
-Visualizing NDVI multi-temporal trends in Sentinel-2 imagery.
-will take the current image as baseline and calculate average NDVI for the previous 2 months
-Based on:
-https://twitter.com/sentinel_hub/status/922813457145221121
-https://twitter.com/sentinel_hub/status/1020755996359225344
+Based on Source: @HarelDan - https://github.com/hareldunn/GIS_Repo/blob/master/Multi-Temporal%20NDVI%20for%20Sentinel%20Hub%20Custom%20Scripts
+Adapted to visualize NDVI for Sentinel-2 quarterly cloudless mosaics by András Zlinszky using GitHub Copilot.
+Each quarter's NDVI is assigned to an RGB channel:
+- Red: NDVI for the oldest quarter
+- Green: NDVI for the middle quarter
+- Blue: NDVI for the most recent quarter
 Script requires multi-temporal processing so parameter TEMPORAL=true should be added to the request.
 */
 
+// How to use this script:
+// Open Copernicus Browser, zoom to your area of interest
+// Select Sentinel-2 Quarterly Mosaics
+// On the date panel, select Time Range mode (calendar icon with from-to arrows on the right side of the date panel)
+// Set the time range - it should be 7 months. This is because the date of a Quarterly Mosaic refers to the first date in the 3 month interval that is used for generating data (https://forum.dataspace.copernicus.eu/t/scenes-getmonth-for-quarterly-mosaics/3045/2?u=andras.zlinszky_education). So eg. if your start date is 2022-01-01 and your end date is 2022-07-01, your are actually looking at images from 2022-01-01 to 2022-09-30
+//  If it is longer, the algorithm will use only the last 9 months
+
 function setup() {
     return {
         input: [
@@ -25,50 +32,47 @@ function calcNDVI(sample) {
     var denom = sample.B04 + sample.B08;
     return denom != 0 ? (sample.B08 - sample.B04) / denom : 0.0;
 }
-function stretch(val, min, max) {
-    return (val - min) / (max - min);
-}
 
 function evaluatePixel(samples, scenes) {
-    var avg1 = 0;
-    var count1 = 0;
-    var avg2 = 0;
-    var count2 = 0;
-    var avg3 = 0;
-    var count3 = 0;
-    var endMonth = scenes[0].date.getMonth();
+    var ndvi1 = 0; // NDVI for the oldest quarter
+    var ndvi2 = 0; // NDVI for the middle quarter
+    var ndvi3 = 0; // NDVI for the most recent quarter
+
+    // Get the quarter of the most recent scene
+    var endQuarter = Math.floor(scenes[0].date.getMonth() / 3);
 
     for (var i = 0; i < samples.length; i++) {
         var ndvi = calcNDVI(samples[i]);
-        if (scenes[i].date.getMonth() == endMonth) {
-            avg3 = avg3 + ndvi;
-            count3++;
-        } else if (scenes[i].date.getMonth() == endMonth - 1) {
-            avg2 = avg2 + ndvi;
-            count2++;
-        } else {
-            avg1 = avg1 + ndvi;
-            count1++;
+        var sceneQuarter = Math.floor(scenes[i].date.getMonth() / 3);
+
+        if (sceneQuarter == endQuarter) {
+            ndvi3 = ndvi; // Most recent quarter
+        } else if (sceneQuarter == endQuarter - 1 || (endQuarter == 0 && sceneQuarter == 3)) {
+            ndvi2 = ndvi; // Middle quarter
+        } else if (sceneQuarter == endQuarter - 2 || (endQuarter == 0 && sceneQuarter == 2) || (endQuarter == 1 && sceneQuarter == 3)) {
+            ndvi1 = ndvi; // Oldest quarter
         }
     }
-    avg1 = avg1 / count1;
-    avg2 = avg2 / count2;
-    avg3 = avg3 / count3;
-    avg1 = stretch(avg1, 0.1, 0.7);
-    avg2 = stretch(avg2, 0.1, 0.7);
-    avg3 = stretch(avg3, 0.1, 0.7);
 
-    return [avg1, avg2, avg3];
+    // Stretch NDVI values for visualization
+    ndvi1 = stretch(ndvi1, 0.1, 0.7);
+    ndvi2 = stretch(ndvi2, 0.1, 0.7);
+    ndvi3 = stretch(ndvi3, 0.1, 0.7);
+
+    return [ndvi1, ndvi2, ndvi3];
+}
+
+function stretch(val, min, max) {
+    return (val - min) / (max - min);
 }
 
 function preProcessScenes(collections) {
-    collections.scenes.orbits = collections.scenes.orbits.filter(function (
-        orbit
-    ) {
+    // Filter scenes to include only the last three quarters
+    collections.scenes.orbits = collections.scenes.orbits.filter(function (orbit) {
         var orbitDateFrom = new Date(orbit.dateFrom);
         return (
             orbitDateFrom.getTime() >=
-            collections.to.getTime() - 3 * 31 * 24 * 3600 * 1000
+            collections.to.getTime() - 3 * 3 * 30 * 24 * 3600 * 1000 // Last 9 months
         );
     });
     return collections;