qWe need to know rij and rgi in order to solve the N linear equation for the N Ps.
q è But we don’t data at grid points
(can not calculated rgi !).
qIt is typical to assume that correlations between points depend only on the distance between
them and not on location or direction.
qSo we calculate the rij from station data and obtain rgi from rij based on the distance between
the grid points and the stations.
q