Yeah- it is hard to tell, although I generally figured that the tripods tower over most buildings and tall trees. If I had to fight these machines , I would shoot the legs- they only have three, and the bigger they are, the harder they fall. But, how big is the alien in comparison to a human?
I was thinking they're probably the same size ish, the alien being taller. I added a dead person on the ground that the alien is standing on, but it's not very obvious