Inverse weighted distance interpolation on a grid.
TT.iwd(tri.data, z.name, geo, css.names = NULL, tri.pol.data = NULL,
text.tol = NULL, text.sum = NULL, blr.clock = NULL,
tri.sum.tst = NULL, tri.pos.tst = NULL, set.par = FALSE,
n = 25, lims = c("points", "triangle")[1], max.dist = NULL,
q.max.dist = 0.5, pow = 0.5)