# Calling linear to converted dB bands and creating few more bands such as VV/VH, VH/VV, VV+VH in function using Google Earth Engine

My question is similar to:

I am new to GEE and JavaScript.

I want to create the following number of bands for each Sentinel1 scene other than original bands (vv,vh in linear scale).

1. RVI, NRPB, VV-db, VH-db, VV/VH (db), VH/VV(db), VV+VH (db).
``````//// RVI calculation
var RVI = vvVhIw.map(function (image){
var rvi = image.expression('sqrt((vv)/(vv+vh)) *  ((4*(vh))/(vv+vh))',
{'vv': image.select('VV'),
'vh': image.select('VH')
}
);
return rvi;
});

// calculate NRPB Band
var NRPB = vvVhIw.map(function (image){
var nrpb = image.expression('(vv-vh)/(vv+vh)',
{'vv': image.select('VV'),
'vh': image.select('VH')
}
);
return nrpb;
});

// convert Linear to DB
var TO_DB = vvVhIw.map(function (image){
var to_db = image.expression('10 * log10(linear)',
{linear: image.select(['VV','VH']),
}
);
});
``````

How to call the VV and VH bands that are in decibel in a function to create bands such as VV/VH (db), VH/VV (db), VV+VH (db). At the end, I will have 7 bands for each Sen1 image.

To begin with, you might want to start off your processing in linear, and convert to dB in the last step. For that, use `COPERNICUS/S1_GRD_FLOAT`. Otherwise, you convert with this:
``````ee.Image(10).pow(db.divide(10))