The problem: Inside a building 9m by 12m, I need to mark horizontal lines around the walls at heights of 3.2m, 3.8m and 4.4m above floor level (assume the existing ground floor is none too level, so I will pick a datum point).
I'm assuming a rotary level is the best tool for the job. I was taught (donkeys years ago) to use a theodolite and surveyors level - so I'm assuming using the modern kit is the same big boys geometry?
Looking in screwfix, there's the cheapy stuff (I'd buy one) or there's the professional stuff (I'd probably hire it).
Is the difference one of durability? Usability? Acuuracy? Are the cheapies in fact near-useless crap for any serious task?
Is the best solution to mark a level baseline on the wall near ground level and then measure up from there at points all around the walls? Or would I be better trying to set the instrument up on a high masonry ledge ? (there's one at slightly more than 3.2m from the ground). That involves more faffing to set it up, but less error over vertical distances (and less object in the laser path to work around) - is it likely to make a scrap of difference anyway?
I'm going to be basing alotof work around this bit of marking out - so I'm willing to go to some trouble to get the most accurate results I can get.