In the bottom right of the image,can be seen,the old quarry at Cawfields(not Roman).Just above that can be seen two parallel mounds.These mark the line of the vallum,which was two parallel ditches,with outcast mounds on either side and between the ditches.It ran almost the full length of Hadrian's Wall,at varying distances from the Wall,sometimes,as at Birdoswald,only a few metres behind the Wall,to almost a mile in places.