The spherical semivariogram model (γ(h)) is represented by the following expression, where h is the lag distance.
\(y(h) = \begin{cases} C_0,\\ C_0+(C-C_0)[1.5\frac{h}{a}-0.5(\frac{h}{a})^3], &\\C, \end{cases}\)
The parameters Co, C and a are respectively known as