According to Dan Hartung :

Why bother with lasers at all? You'll still need to measure distances
manually, either way.

I have one of those 'Strait Line' lasers, and on the package, they
mention "Accuracy: +/- 1/2" at 20 feet". 1 part in 40. Now THAT'S
impressive! Extrapolated over the kind of distances you're working
with, and you could match that precision by throwing darts!

Bleagh! Well, that's the kind of thing I'm finding. Very disappointing.
The hype suggests they're so good they do your laundry too.

1/2" at 20 feet isn't 1 part in 40. It's 1 part in 480 ;-)

Lee Valley occasionally sells an inexpensive laser level (when they get
a shipment of them, for about $23 CDN) and they've tested it and found
it to be 1/4" in 100'.

I have one, and tho I haven't used it much, I believe it.

It's really a matter of how accurate the bubble is and how well you
read it. It's not as if laser light bends much (unless you have a black hole
handy ;-)... If you can calibrate it or slave it off a better level (like
a tested-and-known-good four footer), it would do just about as good as
anything else possibly could. Within range of the spot of course.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.