What is sigma0

Hi Forum,

As in the title, what is sigma0 (as in sigma0 band)?



Scattering coefficient, or the conventional measure of the strength of radar signals reflected by a distributed scatterer, usually expressed in dB. It is a normalised dimensionless number, comparing the strength observed to that expected from an area of one square metre. Sigma nought is defined with respect to the nominally horizontal plane, and in general has a significant variation with incidence angle, wavelength, and polarisation, as well as with properties of the scattering surface itself. See also chapter 3 “Pre-flight Characteristics and Expected Performance” and Backscatter in radar glossary.

‘How strong the radar signals reflected back are’


Many thanks for your comprehensive reply.

1 Like

Sigma0 is the calibrated backscatter coefficient. It is a normalized measure for the intensity of a pixel.

It is based on a calibration constant (often expressed as Beta0) and the incidence angle of the incoming signal:

These might be helpful:
The Radar Backscattering Coefficient
Radar Backscatter
TerraSAR-X - Tipps & tricks


Thanks to Abraun too.

I wasn’t aware of the Earthnet glossary - very useful. I was trying to find answers on google or wikipedia!

Hi Andy,

Would you please to send me the source of this literature http://shodhganga.inflibnet.ac.in/bitstream/10603/78785/11/11_chapter%204.pdf

1 Like

sorry, I also just found this chapter. I don’t have the full book.
The url works for me, do you have problems downloading?

No, it works for me as well, but I’m asking about the title of this book and the year of publishing.

ah, sorry. I don’t know where it is from actually.
I think the chapter is interesting as it compares Beta, Sigma and Gamma. But what I miss is the author’s definition of Gamma. This is nowhere stated and many have different interpretations of it.

If you (or anyone else) is looking for the thesis, it’s here:


1 Like