1

I try to apply an expression to the satellite image and then try to chart the mean of the series of images but I'm getting this error:

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

Link to the code: https://code.earthengine.google.com/c977a6ea5b61ec830b15835036e64c97

Code:

var app = function (image)
{
var conv = image.expression(
    'band/(4.4615*10**-4)',  //formula for coverting mol/m2 to DU(Dobson)
    {
        band: image.select('SO2_column_number_density'),   
  });

return  conv;
};

// Load the sentinel data
var sentinel = ee.ImageCollection('COPERNICUS/S5P/NRTI/L3_SO2')
.filterDate('2019-04-01', '2019-04-21')
.map(app)


//Identify country
var region = ee.FeatureCollection("ft:1p_3AqEj1T9fG0BNu6pGqmP6_HdDOalruzpk54Ne8");
Map.addLayer(region);

Map.addLayer(sentinel)



var TS5 = Chart.image.series(sentinel, region, ee.Reducer.mean(),1000, 'system:time_start').setOptions({
          title: 'pollutants Full Time Series',
          vAxis: {title: 'mol/m2'},
});
print(TS5);
0

using an image expression, the image will losse it's original properties. Copy the properties of the source (image) to the new image (conv):

var app = function (image)
{
var conv = image.expression(
    'band/(4.4615*10**-4)',  //formula for coverting mol/m2 to DU(Dobson)
    {
        band: image.select('SO2_column_number_density'),   
  });

return  ee.Image(conv.copyProperties(image)).set('system:time_start', image.get('system:time_start'));
};
  • Thank you very much that was very helpful. – Mubeen Shafqat May 7 at 13:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.