Error Generating Time Series Chart: No features contain non-null values of "system:time_start"

Question

I'm getting the following error while generating the time series chart for Image Collection:

       Error: No features contain non-null values of "system:time_start".

Here is the code that I have returned for generating the time series chart:

 // Study Area
 var Bhagwanpur = ee.FeatureCollection('projects/ee-omkarjadhav296/assets/Bhagwanpur_Merge');
 Map.addLayer(Bhagwanpur, {}, 'Bhagwanpur', false)
 Map.centerObject(Bhagwanpur, 10);


 // Load the Sentinel-1 ImageCollection, filter to Jun-Sep 2020 observations.
 var sentinel1 = ee.ImageCollection('COPERNICUS/S1_GRD')
                   .filterDate('2021-05-01', '2022-06-05')
                   .filterBounds(Bhagwanpur)


 // Filter the Sentinel-1 collection by metadata properties.
 var vvVhIw = sentinel1
   // Filter to get images with VV and VH dual polarization.
   .filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VV'))
   .filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VH'))
   // Filter to get images collected in interferometric wide swath mode.
   .filter(ee.Filter.eq('instrumentMode', 'IW'));

 print(vvVhIw);

 var RVI = vvVhIw.map(function (image){

   var rvi = image.expression('sqrt(vv/(vv + vh))*(vv/vh)',
     {'vv': image.select('VV'),
      'vh': image.select('VH')
     }

     );

     return rvi;
   })


 var imageVisParam = {"opacity":1,
                      "bands":["VV"],
                      "min":0.01548,
                      "max":0.46221,
                      "gamma":1};

 Map.addLayer(RVI.first().clip(Bhagwanpur), imageVisParam, 'RVI', false);

           /*---------------------------------------------------------*/

 // Plotting of the graph:

 var chart =
     ui.Chart.image.seriesByRegion(
           RVI,
           Bhagwanpur,
           // .filter(ee.Filter.eq('Field_ID', 10)),
           ee.Reducer.mean(),
           'VV',
           10,
           'system:time_start'
         )
         .setSeriesNames(['RVI'])
         .setOptions({
           title: 'RVI',
           hAxis: {title: 'Date', titleTextStyle: {italic: false, bold: true}},
           vAxis: {
             title: 'RVI',
             titleTextStyle: {italic: false, bold: true}
           },
           lineWidth: 5,
           colors: ['#fc0303'],
           curveType: 'function'
         });

 print(chart);

We don't have access to your assets so we can't reproduce the error — Jobbo90
– Jobbo90, Commented Jul 6, 2022 at 9:03
can you please reproduce the result with your assets? as I'm working from the institutional accounts — Reflex_180
– Reflex_180, Commented Jul 6, 2022 at 9:52
No that is your responsibility. You can also create a dummy datasets that also shows your error or problem. — Jobbo90
– Jobbo90, Commented Jul 6, 2022 at 10:58
Ok, sir, I will pass the coordinates to you. Is it ok? because I tried solving the problem but was not able to resolve it — Reflex_180
– Reflex_180, Commented Jul 6, 2022 at 13:55
Coordinates- 'N' Lat- 29.87, 'W' Long- 77.766, 'S' Lat- 29.96, 'E' Long- 77.85 — Reflex_180
– Reflex_180, Commented Jul 6, 2022 at 14:08

xunilk · Accepted Answer · 2022-07-06 16:59:38Z

0

With following correction it will be enough:

 var RVI = vvVhIw.map(function (image){
  
   var date = image.get('system:time_start');
  
   var rvi = image.expression('sqrt(vv/(vv + vh))*(vv/vh)',
     {'vv': image.select('VV'),
      'vh': image.select('VH')
     }

     );

     return rvi.set('system:time_start', date);

   });

I used complete code with point (76.8576, 29.5632) in your ROI. Change for your Bhagwanpur layer in corresponding asset.

After running complete code in GEE code editor, chart was printed without any problem.

answered Jul 6, 2022 at 16:59

xunilk

30.5k4 gold badges44 silver badges83 bronze badges

Thank you so much, sir. It worked for me.

Reflex_180
– Reflex_180

2022-07-06 18:20:14 +00:00
Commented Jul 6, 2022 at 18:20

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