Taking mean of pixel values that buffer contains using Google Earth Engine

Question

I trying to plot the mean of the pixel values that the buffer contains over the given period, but I'm unable to get the mean of pixel values. The link to the code that I wrote is provided below.

Map.addLayer(Bhagwanpur, {}, 'Bhagwanpur', false)
Map.centerObject(Bhagwanpur, 12)
            
Map.addLayer(GT, {}, 'March GT', false)

var CreateBuffer = function(feature, buffer_size) {
  return feature.buffer(buffer_size)
  }

var buffer_size= 10

var GT_Buffer = GT.map(function(ft){return CreateBuffer(ft, buffer_size)});
Map.addLayer(GT_Buffer, {}, 'GT_Buffer')
Map.centerObject(GT_Buffer, 15)
print('GT_Buffer',GT_Buffer)


              /*---------------------------X-------------------------------------*/


// Importing the Sentinel-1 Images:
var S1= ee.ImageCollection("COPERNICUS/S1_GRD")
          .filterDate('2021-05-01', '2022-07-15')
          .filterBounds(Bhagwanpur)
          .select (['VV','VH'])
          .filter(ee.Filter.eq('instrumentMode', 'IW'))
print('S1',S1)


var addVVbyVH = function(image) {
  var vv = image.select('VV');
  var vh = image.select('VH');
  var VVbyVH = (vv).divide(vh).rename('VVbyVH');
  return image.addBands(VVbyVH);
};

var S1 = S1.map(addVVbyVH);
print(S1)


        /*--------------------------------------X--------------------------------------------*/


//Visualization of Images: 
Map.addLayer(S1.first().clip(Bhagwanpur), {'min': [-25, -20, 0], 'max': [5, -10, 5]}, 'S1 RGB', false)


        /*--------------------------------------X--------------------------------------------*/


var chartvv = ui.Chart.image.seriesByRegion(
     S1,
     GT_Buffer.filter(ee.Filter.eq('Field_ID', 5)),
    ee.Reducer.mean(),
    'VV',10)
var chartv2 = chartvv.setSeriesNames(['VV'])
        .setChartType('LineChart') 
        .setOptions({
          title: 'Sentinel-1 time series',
          hAxis: {title: 'Date', titleTextStyle: {italic: false, bold: true}},
          vAxis: {
            title: 'dB values',
            titletext style: {italic: false, bold: true}
          },
          lineWidth: 5,
          colors: ['#fc0303', '#17fc03','#0324fc'],
          curveType: 'function'
        });
        
print(chartv2)

Code: https://code.earthengine.google.co.in/b84ae0181646d5d539e830fd28b55bc7

Answer 1

As your assets are not available, I had to create them as follows:

var Bhagwanpur = ee.Geometry.Point (76.8576, 29.5632);
var GT = ee.FeatureCollection(Bhagwanpur); 

Afterward, I found out that the issue was in the filter in chartvv variable.

var chartvv = ui.Chart.image.seriesByRegion(
     S1,
     GT_Buffer.filter(ee.Filter.eq('Field_ID', 5)),
    ee.Reducer.mean(),
    'VV',10);

I changed it in following way:

var chartvv = ui.Chart.image.seriesByRegion(
     S1,
     GT_Buffer,//GT_Buffer.filter(ee.Filter.eq('Field_ID', 5)),
    ee.Reducer.mean(),
    'VV',10);

and, after running complete code in GEE code editor, I got printed the corresponding chart as follows. So, you need to filter your buffer geometry in a valid way.