“You do what?!”
We’d come across a photo of some American archaeologists (not the one above) taking depth measurements by using a nail, a line level, and a string and I was trying to explain why they were doing this.
“See, you take a nail, and you file a line on it, then you measure its the line’s height from the ground when you pound it in, then you tie a string to that filed line, then whenever you want to measure your unit…”
“Your what?”
“Uhhh, your sub-sectioned, arbitrarily dug context…you pull the string across….”
“What if your context is bigger than a meter wide?”
“You know that they dig in meter squares in America. Following the shape of the actual archaeology is unscientific.”
“But…”
“Yeah. Anyway, so you pull your string across, making sure that the line level’s bubble is in the middle and then you measure to the depth of whatever you are digging, generally to see if your ‘unit’ is dug exactly to a 10 centimeter depth in each unit corner….”
“But what if the context that you are digging is sloped?”
“It’s usually ignored and picked up in the sections. Any finds are pedestaled to maintain these arbitrary levels.”
“Oh. So what happens if it rains or if your nail comes loose? How do you keep track of these randomly assigned heights across an entire site? You know we live in the 21st century, right?”
“Any decent finds are recorded with a total station. If you have one. And there’s someone who knows how to use it.”
“Why not just have an accurately surveyed datum and use a dumpy level?”
“Because whereas meter squares are ultra scientific, actually measuring anything accurately is not. And reducing levels is hard. Math, y’know.”
“Maths.”
“Whatever.”
This conversation has been slightly modified from its original form and content. No American or British archaeologists were harmed in the making of this blog entry. Hopefully.
Colleen Morgan 
this reminds me of some very similar discussions I had with Americans coming over here to dig in France…
One reason for the strings is that most grant-funded U.S. excavations are done on a shoestring budget. NSF and other agencies will simply not give enough funds to buy a bunch of dumpy levels and rods (unless one is doing Paleolithic sites, in which case big budgets are fine). The total station is always off with the mapping crew, who stop by periodically to re-shoot the local excavation datums. That said, I plan to put some dumpy levels into my next budget, after an unfortunate experience with string depths and an inept student on my last excavation.
You should be able to pick up a decent dumpy new for about 200-300.00, the trick is to get one that has a metric staff. I just can’t believe so many professional archaeology firms in the states don’t have one as part of their standard kit.