sentinel1A_ image fusion

I am working on the extraction of water spread area of a can I perform image fusion of sigma not VV, sigma not VH, and MPDI band(microwave polarised differential index) in the SNAP toolbox. I have already tried creat RGB viewoption. and exported the fused image into .bmp format. is this only methodology ?
Please let me know if there are any other…

I guess you are not trying t do data fusion which refers to integrating multiple data sources to produce a final result.

To derive MPDI index, you can use band math. Are you trying to create an RGB image in SNAP including the MPDI results? if you already did that, I do not think there is another way of doing it. Why would you need a different way to achieve the same results with the one provided in SNAP

thanks for responding.
I already performed band math so no worries about that, my concern is about the RGB window option. I want to perform band thresholding on the output using the mask manager option in SNAP in order to catch the water pixels so that I can find accurate water spread area of the reservoir. is there any way to perform band thresholding on RGB image of vv,vh,mpdi

in order to apply a threshold to your data, you do not need to create an RGB image.
You can use Band Maths for that. First of all, check the histogram for each band of your data (vv,vh,mpdi) what the values over water spread look like. Then, you can use band math to write a conditional statement. below i provide a random example as i do not know what you are trying to achieve

if band_vv > thres OR band_vh < thres AND mpdi> thres THEN <some value> else NaN