1

I'm trying to create a time series chart that will tell me that mean precipitation for a given imageCollection, but my polygon is too big and I get the next error message:

"Error generating chart: Collection.first: Error in map(ID=19991001): Image.reduceRegion: Too many pixels in the region. Found 67144509, but only 10000000 allowed."

How can I change the number of pixels and allow it to calculate the mean precipitation value for a given polygon? Whenever I run my code with the big polygon I get the error messege.

This is my code:

var geometry=table;
var dataset = ee.ImageCollection('NOAA/PERSIANN-CDR')
                  .filter(ee.Filter.date('1999-10-01', '2018-03-31'))
                  .filterBounds(geometry);

var precipitation = dataset.select('precipitation');

var onlyPercipitation = precipitation.filter(ee.Filter.calendarRange(10, 3,'month'));
print(onlyPercipitation);

print(ui.Chart.image.series(onlyPercipitation, geometry, ee.Reducer.mean(),30));
3

I got the same problem in one of my project, and came up with a workaround. The idea is to split the chart creation into 2 steps:

  • Reduce each image to the value of interest. This will create a Feature Collection from your Image Collection.
  • Create a chart from the resulted Feature Collection.

Example code:

// Create Feature Collection of mean value
var ft_col = onlyPrecipitation.map(function(img) {
    var date = img.get('system:time_start')
    var mean = img.reduceRegion({
        reducer: ee.Reducer.mean(),
        geometry: geometry,
        maxPixels: 1e13
    }).get('precipitation')
    return ee.Feature(null, { precipitation: mean, 'system:time_start': date })
})
// Create and print chart from ft_col
print(ui.Chart.feature.byFeature(ft_col, 'system:time_start', 'precipitation'))

By using img.reduceRegion, you can specify the maximum number of pixels to reduce via maxPixels. Feel free in increase it if 1e13 is not enough.

P.S. I think you mean onlyPrecipitation not onlyPercipitation in your code?

0

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