GAMMA0 formula

s1tbx
#1

Dear All,
I’m a bit confused about create gamma 0, because My study area is mountainous, i need to create it.

  1. There is an option named ‘‘output as gamma 0’’ in calibration stage (window) as well as when using the Range Doppler Terrain Correction stage in ''Apply Radiometric Normalization". if i want gamma band, which option should I use?
    2.is Gamma (g) the back scattering coefficient normalized by the cosine of the incidence
    angle in calibrate stage? what is the difference between this and radiometric normalization in RD Terrain Correction?

Thanks for your answers.

#2

The only difference is in terrain correction it uses the local incidence angle obtained with the dem.

#3

What works well for me is (after reading some threads on this forum):

calibration to Beta0 -> radiometric terrain flattening to Gamma0 -> terrain correction WITHOUT radiometric normalization.

This produces clean Gamma0 imagery.

3 Likes
#4

Thanks dear lveci for your answer
I have another question:
Where can I find the gamma0 radiometric normalization formula? in the SNAP help file, it just describes for Sigma

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Could you please explain how does Sigma convert into gamma in this formula?
thanks again

#5

You can see from the expression in the virtual band
gamma0 is sigma0 / cos(incident_angle * PI/180.0)
beta0 is sigma0 / sin(incident_angle * PI/180.0)

I’ll update the help to include this.
Thanks

2 Likes
#6

have a look at slides 34ff in this document: https://docplayer.net/12699838-Terrasar-x-products-tips-and-tricks.html

Conventional gamma vs flattened gamma is explained here: https://www.grss-ieee.org/wp-content/uploads/2011/07/IGARSS__RTC.pdf

1 Like
#7

You always give very good documents from many sources, your brain / computer is a library to me :wink: