N_{near}[\tau] = \int_{\tau_1}^{\tau_2} N_{near}(t) dt

N_{far}[\tau] = \int_{\tau_1}^{\tau_2} N_{far}(t) dt

N2F = \frac{ N_{near}[\tau]}{N_{far}[\tau]}

\phi_T = N2F[\tau] + \Delta_{\tau}(\phi_N)

N_{near}(t) = N_{near}(0) \exp ( - t \, \Sigma_{near} )

N_{far}(t) = N_{far}(0) \exp ( - t \, \Sigma_{far} )

\Sigma_{near} = \Sigma_{frm} + \Delta_{near}(\phi)

\Sigma_{far} = \Sigma_{frm} + \Delta_{far}(\phi)

\Sigma_{frm} = (1-\phi) \, \Sigma_m  + \phi \, ( \Sigma_w \, s_w + \Sigma_o \, s_o +\Sigma_g \, s_g)

\delta \Sigma_{frm} \approx +/-1.5 c.u. 

\Sigma_m = \sum_k \Sigma_k

\Sigma_o \approx 18 \quad  11 < \Sigma_o  < 21 

\Sigma_w = 21 + 0.05 * Sal[\rm ppk]

\Sigma_g \approx 3 

\Sigma_{sh} \approx 40 \, c.u. 

\Sigma_{ls} \approx 7 \, c.u. 

\Sigma_m = (1-V_{sh}) \, \Sigma_{snd} + V_{sh} \, \Sigma_{sh}

\Sigma_m = (1-V_{sh}) \, \Sigma_{lms} + V_{sh} \, \Sigma_{sh}