CAVE VOLUME CALCULATIONS AND CORRECTIONS USING THE COMPASS SOFTWARE
A new Cave Volume Tool was created in the spring of 2013 that allows for volume calculations and for determining porosity within cave systems and their host rock. The Cave Volume Tool calculates volumes based on integrating the entire passage into one continuous shape. This tool will be available to the public within the next year.
Cave survey data that is collected using traditional survey methods when put into Compass results in inaccurate volume calculations. This is a result of polygon overlap and incorrect integration of the passage morphologies. With increasing passage complexity (e.g. straight passage to intersections) these volume errors increase. Correction factors have been established using some of the more common cave survey techniques so that more accurate volumes can be calculated. Corrections have been established for straight passages, accurate, obtuse and right angles, intersections, ceiling changes, pits, and chambers / rooms.
By taking multiple random segments of cave survey data the number and abundance of different passage types in each segment can be calculated. Using the correction factors for each passage type a correction factor can then be established for the entire cave system. If cave volume calculations are the end goal for a particular survey, the best way to yield more accurate volumes is through relying on left, right, up and down data associated with each station. The greatest problem with this technique is reconciling floor and ceiling changes with are perpendicular to the survey line. If these data are not available and the cave is relatively short the cave can be resurveyed using its map and the method above to generate accurate volume calculations without the need for the correction factors.