Google Earth Engine MODIS Pixel-sized Spaced Points Position Adjustment

Question

I have managed to export a time series of MODIS daily surface temperature pixel data from the Google earth Engine Code Editor using a combination of code scripts provided by Stack Exchange, here is the link https://code.earthengine.google.com/0949dc53da45580dfaf2131250187847. However the pixel-sized spaced points are not all inside the area of interest, I can`t figure out why and I feel maybe my exported data set includes data from outside the area of interest.

I have also managed to create another code script with the pixel-sized spaced points inside the area of interest, here is the link; https://code.earthengine.google.com/f73a5afed5e813f8b83a528303ab6506. But I can`t manage to combine both codes correctly to export a time series of daily surface temperature pixel data which has all the pixel-sized spaced points inside the area of interest.

Here is the feature collection/function code from the first link which does not have all the pixel-sized spaced points inside the area of interest;

function spacedPoints(fc, proj) {
  var latlon = ee.Image.pixelLonLat().reproject(proj);
  var coords = latlon.select(['longitude', 'latitude'])
                 .reduceRegion({reducer: ee.Reducer.toList(),
                                geometry: fc,
                                scale: proj.nominalScale().toInt()
  });
  var point_list = ee.List(coords.get('longitude')).zip(ee.List(coords.get('latitude')));
  var list = ee.List([0]);
  var feats = ee.FeatureCollection(point_list.map(function(point){
    var ind = point_list.indexOf(point);
    var feat = ee.Feature(ee.Geometry.Point(point_list.get(ind)), {'ID': ind});
    return list.add(feat);
  }).flatten().removeAll([0]));
  return feats;
}

How can I adjust the above code so that all the pixel-sized spaced points are inside the area of interest?

Answer 1

To make sure your collection of points does contain all the center of the pixels, first make a buffer around your area of interest of the size of the pixels. Afterwards, apply filterBounds() to filter out all points outside the region of interest.

Adapt the the geometry argument of reduceRegions as follows:

var coords = latlon.select(['longitude', 'latitude'])
                 .reduceRegion({reducer: ee.Reducer.toList(),
                                geometry: fc.geometry(1).buffer(proj.nominalScale().toInt()),
                                scale: proj.nominalScale().toInt()
  });

And at the last line of the spaced points function, filter out the points outside the region of interest:

return feats.filterBounds(fc.geometry(1));

I think this should return what you expected: link code

Although you could remove a lines from your code using getRegion: see this link