0

This is what I have done so far,

Here's the code,
Link: https://code.earthengine.google.com/6844c4783cd11204e9754e027dd66c3d


var grid = ee.Geometry.Polygon(
        [[[-108.9998, 31.5002],
          [-108.9998, 31.7498],
          [-108.7495, 31.7498],
          [-108.7495, 31.5002]]]);
   
var chirps2021_1 = ee.ImageCollection('UCSB-CHG/CHIRPS/PENTAD')
            .filterDate('2021-01-01', '2021-02-28')
            .filter(ee.Filter.calendarRange(1,2,'month'))
            .filterBounds(grid);

var chirps2021_1_sum = ee.Image(chirps2021_1.sum())

var chirps2021_1_sum_grid = chirps2021_1_sum.clip(grid);

var precipitationVis = {
  min: 0.0,
  max: 112.0,
  palette: ['001137', '0aab1e', 'e7eb05', 'ff4a2d', 'e90000'],
};

Map.addLayer(chirps2021_1_sum_grid, precipitationVis, "Sum January & February 2021 Precipitation", true, 1.0);

Map.centerObject(grid, 0);

And here's the image, enter image description here

As you can see, I clipped the sum of CHIRPS precipitation data to a 0.25-degree grid. And inside the grid, you can observe a 5x5 grid, where each grid is 0.05 degrees, which is the CHIRPS gridded data. Each of the 25 grids has a different precipitation value. For example, the top left grid has a value of 21.11, and the bottom right has a value of 20.15.

What I want to do now is to export the data as a CSV file. Here's the format I want to export; it should be a table with 25 rows corresponding to each CHIRPS grid. The headers for the table would be,

  • Grid Number
  • Precipitation Value
  • Polygon (the coordinates of the grid's polygon) - Optional

1 Answer 1

1

This is one way:

Add this to your code:

//  Create a featurecollection of  each pixel centroids of the image
var pixels = chirps2021_1_sum_13885.multiply(100).toInt().reduceToVectors({
  geometry: grid_13885,
  scale: 5566,
  geometryType: 'centroid',//you can change it to polygons but the result aren't optimal
  labelProperty: 'precipitation',
});

//get lat long
var proj = chirps2021_1_sum_13885.select([0]).projection()
var latlon = ee.Image.pixelLonLat()
chirps2021_1_sum_13885 = chirps2021_1_sum_13885.addBands(latlon.select('longitude','latitude'))

//extract lat, lon and precipitation
pixels=chirps2021_1_sum_13885.select('longitude').reduceRegions(pixels, ee.Reducer.first().setOutputs(['long']), 25)
pixels=chirps2021_1_sum_13885.select('latitude').reduceRegions(pixels, ee.Reducer.first().setOutputs(['lat']), 25);
pixels=chirps2021_1_sum_13885.select('precipitation').reduceRegions(pixels, ee.Reducer.first().setOutputs(['precipitation']), 25);


// Export the feature collection as a CSV file
Export.table.toDrive({
  collection: pixels,
  description: 'grid_13885',
  selectors: ['system:index','precipitation','lat','long'],
  fileFormat: 'CSV'
});

In the end you get the table with: system:id (grid number), lat, lon and precipitation values.

here the link of the code

2

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

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