title: QA with different bits in GEE
body: <p>I face a problem regarding the selection of good quality data of the MCD64A1 burned area product.
  <a href="https://developers.google.com/earth-engine/datasets/catalog/MODIS_006_MCD64A1" rel="nofollow noreferrer">Here</a>, is a description of the QA band but I am really confused with the different bits.</p>
  <p>What I want to do is to select all the
  good quality observations over land and mask the collection based on them. I have the following, but it is nt the right way to do this.</p>
  <pre><code>    var geometry = /* color: #d63000 */ee.Geometry.Polygon(
              [[[23.821277851635955, 46.07285332090363],
                [23.274708027417205, 45.952681148559265],
                [24.11378883796408, 45.554067690813184],
                [24.89381813483908, 45.84372892769175],
                [24.17146706062033, 46.25167241706428]]]);
      var dataset = ee.ImageCollection('MODIS/006/MCD64A1')
                        .filterBounds(geometry)
          .map(function(image){return image.clip(geometry)}) 
                            .filter(ee.Filter.calendarRange(7,7,'month'));
      var burnedArea = dataset.select('BurnDate','QA');
  
  //good quality observations
  
  var good= (function(img) {
    var goodQA = img.select(&quot;QA&quot;).eq(1); 
    return img.updateMask(burnedArea .and(goodQA));
  });
  </code></pre>
  <p><strong>EDIT</strong></p>
  <p>Also, I have tried the following which gives me no error but also no data.</p>
  <pre><code>var good= function(img){  
    var qa = img.select(['QA']);
    var mask = qa.bitwiseAnd(0).eq(1).and( 
               qa.bitwiseAnd(1).eq(1)).and( 
               qa.bitwiseAnd(2).eq(1)); 
    return img.updateMask(mask);
  };
  </code></pre>