ControlPoint Manual — versioned with the code; every worked example below is a REAL corpus job and its numbers are pinned by the test suite.
2 — Heights
What it does
The Heights panel shows every setup's instrument height (HI) and each target height (HT). Heights of 0 or 0.240 m mean forced centring (pillar/prism on a stud); a measured tripod height (say 1.765) means set up over a nail, which costs about ±1 mm of centring accuracy — the weighting knows this. Setups whose HI can't be trusted can be trig heighted: reciprocal vertical angles solve the true HI, with a significance gate so a correction is only applied when the evidence clears 2σ.
Worked example — 2HR19, setup N27
N27's booked HI was wrong by about 5 mm. Trig heighting solved a correction of +4.9 ± 1.1 mm; applying it took the network's error factor from 0.632 to 0.462 and cleared all eight reciprocal-zenith failures. The report's HI history block shows recorded value, applied value, correction and sigma — nothing is overwritten silently.
Theory in one paragraph
A wrong HI shifts every vertical observation from that setup by the same amount, and reciprocal observations see it with opposite sign. That asymmetry is what lets least squares solve for the HI as an unknown — and why the check is trustworthy: other setups' pairs must agree before the software blames the HI.