# N_sigma_bs

N_sigma_bs is an analysis variable useful for the purposes of biomass estimation.

Let D be the domain over which the sample mean is to be calculated.

Then N_sigma_bs is calculated as follows:

Where:

N = Number of fish in the domain D (-)

sbs = Expected backscattering cross-section of an individual fish in the domain D (m2)

sv = The linear mean Sv for all samples in the domain D (m2/m3)

V = the integration volume (m3)

and

Sv_mean and Volume_integration are the respective analysis variables with those names.