The use of transparent drawing film must have been a huge help in
digging stratified sites because it allowed the multiple overlay of
plans without the distortion and other problems of tracing paper- a key
aspect of open area excavation techniques on stratified sites from hill
forts and monasteries to urban tenements. I asked a few colleagues this
morning and we couldn't fix its introduction into archaeological use
(?1960s) but remembered graph paper still being use in the early 70s on
some sites and drawing film on others presumably with more money.
paul