How would I calculate the sum of the values of a band around a specific pixel in Google Earth Engine?

Question

I'm trying to calculate the population within a certain radius around a specific pixel, but I don't know how to define the geometry of the region to reduce.

This is what I would imagine it might look like, where "clipped" is the overall region:

var radiusPop = clipped.reduceRegion({

reducer: ee.Reducer.sum(),

geometry:

scale: 30,

maxPixels: 1e9

});

Essentially I'm trying to add a band to my image that contains the population within a certain radius around the pixel. I can't figure out how to define the geometry for each pixel.

Answer 1

There are several ways to do this. You can for instance use reduceNeighborhood() to calculate the sum around all the pixels in the image, controlling the "geometry of the region to reduce" with the kernel. Then you extract the value for a specific pixel with reduceRegion().

var populationSum = clipped.reduceNeighborhood({
  reducer: ee.Reducer.sum(), 
  kernel: ee.Kernel.circle(200, 'meters'), // Control 
  inputWeight: 'mask'
})

var populationAroundPoint = populationSum.reduceRegion({
  reducer: ee.Reducer.first(), 
  geometry: point, 
  scale: 100, 
}).getNumber('population_sum')

https://code.earthengine.google.com/329c5e5109cecae8dcb70ab44bf81609