This is one of the reasons that for legs like that (where the Disto will be 
parallel to a wall not perpendicular to it during the next shot), we aim the 
laser not for the station itself, but for the middle of a small block that is a 
similar size to the Disto, held on the station. The easiest thing to use is the 
nail varnish bottle which will be used to physically paint semi-permanent 
stations. It is easier to see from a distance, and it removes angular and 
distance errors you mention. And the person holding the nail varnish can 
clearly identify whether the Disto missed the target.For calibration, I get a 
typical error of around 0.3 or below. All metal objects are removed first: 
tripods, tackle bags, krabs, belt, Android device, stylus, helmet, light, SRT 
gear, wedding ring, watch, safety knife, etc.. And avoid fixed aids like bolts 
or cables, or areas with scaffolding or fences and gates, or reinforced 
concrete in the cave.I use obvious natural marks on the walls for all points of 
the calibration, aiming from one to the opposite one, about 3 metres (10 feet 
ish) apart. Then the opposing measurement in the opposite direction. This is 
done for all measurements, horizontal, vertical and diagonal.When the cave has 
natural minerals, avoid those areas during calibration. For our lead mine 
surveys, we calibrate in a local forest where there are no minerals.
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