Filtering region of interest in Sentinel 5P image collection?

Question

I want to simply filter an Image Collection for a set of Spatial coordinates. However, the built-in Filterbounds function does not seem to work. I did try researching and the only answer I got to my question was that filterbounds does not work due to global coordinate system (Or I think this is what it means)

This is the code in which I was not able to make any further progress.

var roi = ee.Geometry.Polygon(
    [[[-107.416796875, 36.750944433035215],
      [-107.416796875, 34.53706063512119],
      [-102.934375, 34.53706063512119],
      [-102.934375, 36.750944433035215]]], null, false);


var collection = ee.ImageCollection('COPERNICUS/S5P/OFFL/L3_NO2')
  .select('NO2_column_number_density')
  .filterDate('2019-06-01', '2019-06-06')
  .filterBounds(roi);
  


var band_viz = {
  min: 0,
  max: 0.0002,
  palette: ['black', 'blue', 'purple', 'cyan', 'green', 'yellow', 'red']
};

Map.addLayer(collection.mean(), band_viz, 'S5P N02');
Map.setCenter(65.27, 24.11, 4);

Can someone demonstrate how to filter spatially?

Answer 1

Jobbo90 is right, you could just do your mean first, then clip the image to your ROI.

However, if for some reason you are still interested in doing a "spatial filter" on the entire collection, use .map(function(image){return image.clip(roi)}) instead of filterBounds(). I've attached an improved version of your code below.

Note: your Map.setCenter() coordinates did not center on your roi, so I change that for you too.

var roi = ee.Geometry.Polygon(
    [[[-107.416796875, 36.750944433035215],
      [-107.416796875, 34.53706063512119],
      [-102.934375, 34.53706063512119],
      [-102.934375, 36.750944433035215]]], null, false);
    
Map.addLayer(roi)

Map.centerObject(roi,6)

var collection = ee.ImageCollection('COPERNICUS/S5P/OFFL/L3_NO2')
  .select('NO2_column_number_density')
  .filterDate('2019-06-01', '2019-06-06')
  .map(function(image){return image.clip(roi)});

var band_viz = {
  min: 0,
  max: 0.0002,
  palette: ['black', 'blue', 'purple', 'cyan', 'green', 'yellow', 'red']
};

Map.addLayer(collection.mean(), band_viz, 'S5P N02');

Answer 2

The Sentinel 5 dataset seems to hold all observations from 1 orbit:

From the data description (link):

The OFFL assets contain data from a single orbit (which, due to half the earth being dark, contains data only for a single hemisphere).

So 'filtering' spatially as you call it doesn't make any sense. You could apply a clip if you just want the area you are interested in:

Map.addLayer(collection.mean().clip(roi), band_viz, 'S5P N02');

https://code.earthengine.google.com/0978414864437a84281bdfb1802cc3fd