1mm (0.0393701 inch) at 10 meters (393.701 feet).
As Oxbow mentioned: Those are BIG meters Tinkerer! (Just teasing)
How about 10 meters = 32.8083 feet
The EXACT (by definition) is 25.4 mm = 1 inch
The 'accuracy' of the high price units is determined by the 'auto leveling'
I could check the accuracy of the most expensive for 'auto leveling' even the dual slope.
It is just a matter of setting the laser spinner to a known point and checking where the $$$$ units point to. That is just basic.
My Major in college was Physics.
Einstein was wrong as the speed of gravity (or it's effect) travels 1,000 of times faster than light.
http://www.ldolphin.org/vanFlandern/
Time/light speed is affected to a small extent by the magnitude of the gravitational field it travels through. All the GPS satellites compensate for that.
Some of the new GPS units have a resolution of .0001 foot (just guessing as it has been a while since reading on that) and the accuracy is nearly that.
Who cares?? The tectonic plates are moving so in a few months the readings will be different at that resolution.
Also with the curvature of the Earth over a half mile distance the 'level' has about 1/2 inch in the middle that is 'lower' in line of sight than it's 'altitude'. Just basic algebra.
I will use the $50 HF units even if I had a couple $$$$ units in a box.
It takes more time setting at least two points first but I KNOW where I am at.