Length, bearing, inclination, station to station. There is no GPS down here and there never will be — a cave map is the accumulated arithmetic of a tape and a compass, and the only check on it is that the loops come back to themselves.
Survey round to where you started and you will not arrive exactly. The gap is the misclosure, and as a fraction of the distance walked it is the one number that says whether the survey is any good. Then it is distributed back along the loop in proportion to each leg's length — Bowditch's rule — because a long shot has had more opportunity to be wrong than a short one.
A survey is quoted with the grade it was made to, because a map drawn from body-length estimates and one made with a calibrated instrument are different documents. The grade is a statement about the instruments and the discipline, not about how neat the drawing is.
| grade | what it means |
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Random errors in bearing and length grow as the square root of the number of shots, not in proportion to it — which is why a hundred careful short shots can beat ten long sloppy ones, and why one systematic error, like an uncorrected declination, is worse than all the random ones together.
The rock the cave is in, and whether the water in it is aggressive enough to have dissolved this much, are Water chemistry — a calcite saturation index below zero is a passage still being enlarged. And radon is the exposure that matters underground, where there is no ventilation but what you brought.