I place my Sat Nav in the corner of my windscreen, which corner depends on the direction of travel, if travelling north I place in top right hand, south at bottom right hand and so on.
I find that this better aligns my Sat Nav with the satellite, Only if i were travelling at, or near the North Pole would I then draw diagonal lines from corners to corners on my windscreen thus establishing dead centre and place my Sat Nav there for perfect alignment.