Fig. 9
From: Geographical model-derived grid-based directional routing for massively dense WSNs
A piecewise-linear finite element basis function. The linear basis function μ
i,j
is a pyramid with the peak at 
and is nonzero only within the element centered at 
(i.e., the gray hexagon). In addition, (x
i
,y
j
) is the position of 