Google Earth Engine – How to Combine Two Image Overlays into One Image

google-earth-engineimage

I have two images of different sizes. I can make them overlay each other using Map.addLayer() for each. But I want to combine them into one image as shown in illustration below. How to achieve this?

Best Answer

Never mind my impatience,

It was easy. I just convert them to image collection and then create mosaic of it!

var combined_img = ee.ImageCollection([img_1, img_2]).mosaic();

Related Solutions

Google Earth Engine – Combine MOD13Q1 and MYD13Q1 Collections

My guess is you are trying to combine the two 16-day composites into a synthethic 8-day composite containing data from both Aqua and Terra (as has been proposed in many research papers).

You can do this by simply merging both collections and then sorting according to the central acquisition date.

https://code.earthengine.google.com/84430216d1ce67eeeb7f067dd6db581e

// Load MODIS MOD13Q1 dataset.
var MOD13Q1 = ee.ImageCollection('MODIS/MOD13Q1')
  .select('NDVI')
  .filterDate('2015-01-01','2017-12-31')
  .filterBounds(roi)
print(MOD13Q1);

// Load MODIS MYD13Q1 dataset.
var MYD13Q1 = ee.ImageCollection('MODIS/MYD13Q1')
  .select('NDVI')
  .filterDate('2015-01-01','2017-12-31')
  .filterBounds(roi)
print(MYD13Q1);

// merge collections
var MOD_merged = MOD13Q1.merge(MYD13Q1)
print(MOD_merged)

// sort by date
var MOD_merge_sorted = MOD_merged.sort("system:time_start")
print(MOD_merge_sorted)

[GIS] Merging two image collection into one with two bands (LST and NDVI )

You should show more effort and paste some code, what you have tried. But anyhow, I think this is what you want:

// Collections
var mod1 = ee.ImageCollection("MODIS/006/MOD11A2");
var mod2 = ee.ImageCollection("MODIS/006/MOD13Q1");

// Some dates to filter
var d1 = ee.Date.fromYMD(2017,1,1)
var d2 = ee.Date.fromYMD(2017,3,1)

// filter collections and select needed bands
mod1 = mod1.filterDate(d1, d2).select('QC_Day')
mod2 = mod2.filterDate(d1, d2).select('NDVI')

// Use an equals filter to define how the collections match.
var filter = ee.Filter.equals({
  leftField: 'system:index',
  rightField: 'system:index'
});

// Create the join.
var simpleJoin = ee.Join.simple();

// Applt join
var mod1join = ee.ImageCollection(simpleJoin.apply(mod1, mod2, filter))
var mod2join = ee.ImageCollection(simpleJoin.apply(mod2, mod1, filter))

print('Joined', mod1join, mod2join)

var final_col = mod1join.map(function(img){

  // Create a collection with 1 image
  var temp = ee.ImageCollection(ee.List([img]));

  // Apply join to collection 2
  // Resulting collection will have 1 image with exact same date as img
  var join = simpleJoin.apply(mod2join, temp, filter);

  // Get resulting image
  var i2 = ee.Image(join.first())

  return img.addBands(i2)
})

print(final_col)

Best Answer

Related Solutions

Google Earth Engine – Combine MOD13Q1 and MYD13Q1 Collections

[GIS] Merging two image collection into one with two bands (LST and NDVI )

Related Question