Filtering ImageCollection based on set value using Google Earth Engine JavaScript API

Question

I would like to filter ImColl based on the value of sum of clouded pixels; filter in script (not activated) doesn't do the job. And also the mapped cloud band is not the 'same' as reducer value, which is not error from code. Run the link to see outputs.

Can you help me solve this?

var start = '2020-02-15';
var end = '2020-02-18';
var viz = {min:0,max:0.8,palette:['#b88c0b','#cebc2d','ffd32c','#f7f217','f1ff33','d1ff4b','79ff6a','6beb4c','52b43a','#26a025']};

var MODIS_GAmap = ee.ImageCollection("MODIS/061/MOD09GA").filterDate(start);
Map.addLayer(MODIS_GAmap,{'bands':['sur_refl_b01','sur_refl_b04','sur_refl_b03'],min:30,max:1990},'rgb');
print(MODIS_GAmap,'maped');

var MODIS_GA = ee.ImageCollection("MODIS/061/MOD09GA")
                       .filterDate(start,end)
                       .map(function(i){
            var clip = i.clip(table);
            var QA = clip.select('state_1km');
            var cloud = ee.Image(QA.bitwiseAnd(1<<0).eq(1).rename('cloud'));
            var C_sum = cloud.reduceRegion({reducer:ee.Reducer.sum(),geometry:table,scale:500}).values();
            var ndvi   = clip.normalizedDifference(['sur_refl_b02', 'sur_refl_b01']).rename('NDVI_GA');
            
    return ee.Image([ndvi,cloud]).set('system:index',i.get('system:index'))
                                     .set('Cl_px_sum',C_sum)});//.filter(ee.Filter.lt('Cl_px_sum',75))});  //++DOESN'T WORK

print('Cloud px no.=', MODIS_GA.aggregate_array('Cl_px_sum')); //max study area=267 GA_px 
print(MODIS_GA);
Map.addLayer(MODIS_GA.select('cloud'),{},'cloud'); //++ reducer.sum returns value 0(cloudfree) for first date, but on map some values are 1    
Map.addLayer(MODIS_GA.select('NDVI_GA'),viz,'NDVI_GA');

link to code GEE:https://code.earthengine.google.com/08d65a0453ebf88d0fbda528f523d3f6

Miha Žemva · Accepted Answer · 2025-10-26 16:01:55Z

0

Problem solved.


var C_sum=cloud.reduceRegion({reducer:ee.Reducer.mean(),geometry:table,scale:500});
var C_sumN = C_sum.getNumber('cloud');

.................
    return ee.Image([ndvi, cloud]).set({'CLOUDINESS':C_sumN})});
..................
Map.addLayer(MODIS_GA.first().select('cloud'),{},'cloud');

Now the filter works. Yee yupi.

edited Oct 26 at 16:01

answered Oct 24 at 23:47

Miha Žemva

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