Sigma0_IW2_VV_db

Microwave Toolbox Interferometry
#1

Dear all,
I have one question. I had ‘Sigma0_IW2_VV’, then as I need it in db. I used
Raster----data conversion----linear to/from db.
Now I have two bands.

  1. Sigma0_IW2_VV
  2. Sigma0_IW2_VV_db

I want to save ‘ Sigma0_IW2_VV_db’ in Geotif. I am using
File—export----geotiff—subset-----I check only ‘Sigma0_IW2_VV_db’----but I got one massage (look at below).

error2.jpg650×655 55.2 KB

then

eror4.jpg923×772 129 KB

When I open geotiff in QGIS, it is not ‘Sigma0_IW2_VV_db’ while it is Sigma0_IW2_VV. I do not know what can I do for having ONLY ‘Sigma0_IW2_VV_db’ in QGIS.
Cheers,
Marjan

#2

If the dB-band is virtual you need to convert it to a real band before you can delete the linear one.

#3

How can I do that?

#4

Dear friend,
As you told me I should convert virtual ban to a real band before you can delete the linear one. I did that by this steps:
Rater—Data conversion----convert data type----processing parameters (I only chose ‘Sigma0_IW2_VV_db’). I can open it but I do not know why minimum and maximum amount before and after conversion is difference now? Which one it correct, before conversion or after conversion?
Cheers,
Before conversion:

db_before_conversion.jpg954×715 86.7 KB

After conversion:
db_after_convertion.jpg963×698 81.6 KB

#5

maybe Geotiff cannot handle negative values (signed integer). The db values ranging from -40 to +5 are the correct ones.

#6

OK but I can not see values ranging from -40 to +5. Do you mean -24.861 to 0.081?