Computing MNDWI for Sentinel 2 Images in Google Earth Engine?

Question

MNDWI is the normalized difference of Green Band and SWIR Band. In LANDSAT both are of a similar resolution i.e. 30m.

In the case of LANDSAT

var landsat8 = ee.Image("LANDSAT/LC08/C01/T1_RT_TOA/LC08_148044_20130425")
var ndwi = image.normalizedDifference(['B3', 'B6']).rename('MNDWI')

gives us MNDWI Band

whereas in the case of Sentinel 2 the resolutions of Green Band (B3 is 10m) and SWIR Band (B11 is 20m) are different.

How to change SWIR Band to more finer resolution so that I can apply normalized difference?

Answer 1

You might want consider going through the earth engine documentation: https://developers.google.com/earth-engine/resample

Basically you want to define the projections of both bands before doing the calculation. Changing the scale suggests you need to set the scale parameter in .reproject()

I guess you could following this workflow: https://leclab.wixsite.com/spatial/post/pansharpening-sentinel-2-imagery-in-google-earth-engine

Answer 2

normalizedDifference(['B3', 'B6']) means (Band 3-Band 6)/(Band 3 + Band 6), what you need to do is substitute the band number as you wish.