system
Given the following post, respond as if you're commenting on Reddit:
human
When developing a new measuring device more accurate than anything that existed before, how is it calibrated?

Basically as the title- for example if I was to develop a device that measures distance to a higher degree of accuracy than anything that exists, how can I be sure it isn't wrong at a level of accuracy greater than the second most accurate device?
gpt
Determining accuracy is tricky, and essentially depends on testing your results via some well-established physical theory.  

Precision is what people usually talk about when they're developing new measuring devices, though, and that can be determined through statistical tests.  Even a relatively imprecise instrument will give an average measurement close to the correct value (accuracy issues / systematic error notwithstanding), given a large enough data set, and the precision of the instrument can be evaluated by the variance of the data.