Google Earth Engine – Filtering Images That Completely Overlap Area of Interest

filtergoogle-earth-engine

I have a Sentinel 1 image collection and I want to filter the images that completely overlap my region of interest. filterBounds() keeps the images that partially overlap my ROI. While browsing the GEE documentation I found ee.Filter.contains(), however I did not understand the inputs of the function.

I tried the following but it didn't work

var imageCollection = ee.ImageCollection("COPERNICUS/S1_GRD");
var S1_filtered = imageCollection.filter(ee.Filter.contains(geometry))

Map.addLayer(S1_filtered)

where geometry is a rectangle that I drew on the map having the following coordinates:

coordinates: List (1 element)
    0: List (5 elements)
        0: [11.242486382607296,53.14196639066307]
        1: [11.720391656044796,53.14196639066307]
        2: [11.720391656044796,53.48654847659319]
        3: [11.242486382607296,53.48654847659319]
        4: [11.242486382607296,53.14196639066307]

When I run this code I obtain the following error message:

Layer 1: Layer error: String: Unable to convert object to string.

How can I use ee.Filter.contains() to filter an image collection with a polygon?

Best Answer

If you use positional (rather than named) arguments with ee.Filter.contains, you must pass them starting with leftField, rightValue, .... That is, the first argument is a property name, and the second argument is the value to compare with. Since you want to match against the feature's main geometry, you pass the special string '.geo' as the property name.

imageCollection.filter(ee.Filter.contains('.geo', geometry))

However, this will be quite slow, as this filter is not currently optimized like the extremely common intersection filter (filterBounds) is. So, you can improve the performance by also using filterBounds().

It will also help to choose a date range rather than requesting a mosaic of all the S1 images ever.

var imageCollection = ee.ImageCollection("COPERNICUS/S1_GRD");

var S1_filtered = imageCollection
    .filterBounds(geometry)
    .filterDate('2022-01-01', '2022-02-01')
    .filter(ee.Filter.contains('.geo', geometry));

Map.addLayer(S1_filtered);

Related Solutions

Google Earth Engine – Mapping Over List of Dates

The error

ImageCollection.fromImages: Attempt to create an ImageCollection with non-image elements.

will occur if you are attempting to create an image collection from a list of null objects. In your code, this will occur if you attempt to take the .first() element of an empty month-filtered S1 collection. The following code demonstrates this, by filtering the monthly collections to a region in the ocean where no Sentinel-1 images have been collected:

var geometry = ee.Geometry.Point([-136.14, 35.17]);
var Date_Start = ee.Date('2015-05-01');
var Date_End = ee.Date('2017-12-01');
var Date_window = ee.Number(30);

// Create list of dates for time series
var n_months = Date_End.difference(Date_Start,'month').round();
var dates = ee.List.sequence(0,n_months,1);
var make_datelist = function(n) {
  return Date_Start.advance(n,'month');
};
dates = dates.map(make_datelist);

var fnc = function(d1) {
  var start = ee.Date(d1);
  var end = ee.Date(d1).advance(1,'month');
  var date_range = ee.DateRange(start,end);
  var S1 = ee.ImageCollection('COPERNICUS/S1_GRD')
    .filterDate(date_range)
    .filter(ee.Filter.listContains('transmitterReceiverPolarisation', 'VV'))
    .filter(ee.Filter.eq('instrumentMode', 'IW'))
    .filterBounds(geometry);
  return(S1.first());
};

var list_of_images = dates.map(fnc);
print('list_of_images', list_of_images);
var mt = ee.ImageCollection(list_of_images);
print(mt);
Map.addLayer(mt, {}, 'mt');

If you instead you modify the filters so that at least one of the monthly collections has an image, the error will be avoided and your object mt will be a valid image collection.

[GIS] Filtering Image in Google Earth Engine based on metadata

Stephen Van Gordon from the GEE users group was able to steer me in the right direction. As I suspected, filter operations are intended only for ImageCollections, not Images.

There are two main options to complete the task I intended. One is to use ee.Image().eq operators to chain together values of interest.

A more comprehensive way is to store the values I care about in an ee.List object and then use Image.remap, which will allow me to map all the desired classes to 1 and everything else to 0.

var cdl= ee.Image('USDA/NASS/CDL/2017').select('cropland')

 var crops=ee.List([1,4,5,7,9,10, 31, 33, 36, 45, 63, 64, 86, 241])

// Only pull two crop types for demonstration purposes.
 var mask = ee.Image(cdl)
  .eq(152)
  .or(cdl.eq(1))
var masked = ee.Image(cdl)
  .updateMask( cdl.eq(152).or(cdl.eq(1)) )

// Map.addLayer(filtered)
Map.addLayer(mask, {}, 'mask')
Map.addLayer(masked, {}, 'masked')

var remapped = cdl.remap({
  from: crops,
  to: ee.List.repeat(1, crops.size()),
  defaultValue: 0
})

Map.addLayer(remapped, {}, 'remapped')

Best Answer

Related Solutions

Google Earth Engine – Mapping Over List of Dates

[GIS] Filtering Image in Google Earth Engine based on metadata

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