How to mosaick two raster images (NDVI and NDWI) as one layer in GEE? (Python)

[IndigoWizard]

Important

• Don't forget to check the CONTRIBUTING.md
• This issue is related to the feature/imagery-analysis branch and so should the PR come from it (or make a new branch with prefix Imagery-) and it shall be merged into the develop branch.

Main issue gist

(original question asked in here in gis.stackexchange.com/questions/436671/

I'm trying to mosaic NDVI and NDWI layers into one layer using GEE (python). This is for having land part of the map covered by the NDVI results and the water part of the map covered by NDWI. All that in one layer.

Any idea how to make this work?

See here for reference: Google Earth Engine: Image Visualization

Visuals

Wanted result	Similar to
Mosaic of NDWI & NDVI as one layer	Mosaic of NDWI & False Color Composite

The problem

• Simply not working.
• No errors.
• "Mosaic: NDWI x NDVI" layer exist but not showing visuals.
• "Clipped: NDWI x NDVI" layer exist and only showing NDVI land part but in a grey scale colors, not original NDVI palette. The NDWI part of the mosaic is left out not showing.

my actual results-1 (problem)	my actual results-2 (problem)
Clipped mosaic of NDWI & NDVI as one layer Greyed out and no NDWI	Nothing shows on the map (Mosaic of NDWI & NDVI not working)

My approach

I first followed the official tutorial in GEE documentation (see here: https://developers.google.com/earth-engine/guides/image_visualization#mosaicking).

• Managed to reproduce the results and successfully mosaicked NDWI & FCC (false color composite) as one image layer.
• I tried to mosaic NDWI and NDVI but no results show up in that layer. No errors of execution in the console tho.

[IndigoWizard]

After a long while I found a solution to the issue. The idea is to combine the two images I wanted to merge into an ee.ImageCollection then mosaicking the two using .mosaic() function.
It is still tricky to get the color palette to apply on the right pixel value range within the mosaicked raster but with the help of a mask and a binary mask the outcome is closer to what is intended in the final result.
Still needs some tweaking but it works.

See: https://developers.google.com/earth-engine/apidocs/ee-imagecollection-mosaic