[GIS] Filter Image Collection by Multiple WRS Path/Rows using Google Earth Engine JavaScript API

google-earth-enginegoogle-earth-engine-javascript-api

How can I filter an image collection in Google Earth Engine by multiple WRS paths/rows?

This is an example of a filter using one path.row:

var sr2011 = ee.ImageCollection('LANDSAT/LT5_SR')
  .filterDate('2011-06-20', '2011-08-31')
  .filter(ee.Filter.eq('WRS_PATH', 59))
  .filter(ee.Filter.eq('WRS_ROW', 18));

Best Answer

Try combining AND and OR filters or, if more complicated, you could look into ee.Filter.inList:

var sr2011 = ee.ImageCollection('LANDSAT/LT5_SR')
  .filterDate('2011-06-20', '2011-08-31')
  .filter(ee.Filter.or(
    ee.Filter.and(ee.Filter.eq('WRS_PATH', 59),         
                  ee.Filter.eq('WRS_ROW', 18)),
    ee.Filter.and(ee.Filter.eq('WRS_PATH', 60), 
                  ee.Filter.eq('WRS_ROW', 19))))

This works but capitals are needed on ee.Filter.Or and ee.Filter.On

Related Solutions

Landsat – How to Apply a Cloud Filter to Landsat8 Collection in Google Earth Engine

You need to check how Image.reduceRegion works. From documentation:

reduceRegion(reducer, geometry, scale, crs, crsTransform, bestEffort, maxPixels, tileScale)

Apply a reducer to all the pixels in a specific region. Either the reducer must have the same number of inputs as the input image has bands, or it must have a single input and will be repeated for each band. Returns a dictionary of the reducer's outputs.

Arguments:

this:image (Image): The image to reduce.

reducer (Reducer): The reducer to apply.

geometry (Geometry, default: null): The region over which to reduce data. Defaults to the footprint of the image's first band.

...

maxPixels (Long, default: 10000000): The maximum number of pixels to reduce.

Change this argument to avoid this error message:

var cloudiness = cloud.reduceRegion({
reducer: 'mean', 
geometry: S_sudan, 
scale: 30,
maxPixels: 1e10
});

Google Earth Engine – Calculating Image Collection Statistics in Google Earth Engine

Earth Engine provides very nice functionality to calculate statistics on imagery called reducers. There are plenty of ways to use reducers but as simple examples you can calculate the statistics at the pixel level or provide a geometry to calculate statistics:

var modis = ee.ImageCollection("MODIS/006/MOD13Q1")
.filterDate("2000-01-01","2001-01-01")
.select("NDVI");

print(modis)

var mod13 = modis.map(function(img){
  return img.multiply(0.0001)
  .copyProperties(img,['system:time_start','system:time_end']);
});

// calculate the mean of value for each pixel
var meanMod13 = mod13.reduce(ee.Reducer.mean())
Map.addLayer(meanMod13,{min:0,max:1},'Mean NDVI')

// calculate the mean value for a region
var geom = ee.Geometry.Rectangle([-88,34,-87,35])
Map.addLayer(geom)
// *Note that reduceRegion works only on ee.Image not ee.ImageCollection data types
var zonalStats = meanMod13.reduceRegion({
    geometry: geom,
    reducer: ee.Reducer.mean(),
    scale: 1000,
    bestEffort: true
});
print(zonalStats)

I hope this helps!

Best Answer

Related Solutions

Landsat – How to Apply a Cloud Filter to Landsat8 Collection in Google Earth Engine

Google Earth Engine – Calculating Image Collection Statistics in Google Earth Engine

Related Question