yr = y + randn(2048, 2048)
xr = x + randn(2048, 2048)
zn = griddata(xr.ravel(), yr.ravel(), z.ravel(), x, y)
zl = griddata(xr.ravel(), yr.ravel(), z.ravel(), x, y, interp='linear')
2D Interpolation of Large Irregular Grid to Regular Grid