The Kriging method needs to compute semi$-$variance y to a set of lag distance $($h$).$ A semivariance is defined as below using a specific formula to $h.$ Calculate semi$-$variance $y(h)$ to $h=5,10,15km.$

$(h)=\frac{1}{2}n*{\displaystyle \underset{?}{\overset{?}{}}}(z_o-Z_b{)}^2$

where $Z_a$ is the variable measured at one point, $Z_b$ is the variable measured at another point $h$ distance away, and $n$ is the number of pairs that are approximately the distance $h$ apart.

Figure B$.$ the lag distance for tnree odservation points.