A NEW CAVE SURVEY TECHNIQUE FOR IMPROVING 3D RENDERING AND VOLUMETRIC ACCURACY WITHIN THE COMPASS SOFTWARE

Cave mapping is an integral part of karst research. Current cave survey methods used in karst science are well suited to the task of making plan view illustrative maps of a given cave, they are however of limited use when attempting to make estimates of a cave volume and 3-D representations. This is due to prevailing survey methods that focus on maximizing total survey coverage, relying heavily on a surveyor’s personal ability to estimate cave dimensions while detailing the sketch. Traditionally, survey stations—where the various data points are taken—are daisy chained throughout a cave system in such a way as to maximize coverage while minimizing stations. This usually results in stations being placed at changes in passage direction and identifiable landmarks.

Our method was developed from the beginning with the intent of producing accurate 3D models in Compass (a freeware computer program), with a focus on improving the accuracy of volume estimates. While the data taken at each station is the same as traditional methods, the station placement is fundamentally different. Rather than allowing the passage and line of sight to determine station placement, stations are placed at a central location in the passage at each change in passage morphology—be it wall, ceiling, and/or floor. This method was tested not only on idealized passage shapes, but on three flank margin caves and three littoral caves on Eleuthera, The Bahamas. The new cave survey methods were then compared directly to traditional surveys of these same caves performed by other surveyors. The new survey technique did not greatly increase the number of stations or the total survey time, but it made significant improvements in the accuracy of the cave renderings and cave volumes.

Beyond that, a second-pass refinement of our data was made by drafting our maps using Adobe Illustrator and standard plan view mapping techniques, then re-surveying these maps by hand—adding many more stations, and subsequently many more data points. This resulted in another increase in cave rendering and volume accuracy, at no cost of additional time in the field. The combination of these surveying techniques provides a massive increase in 3D modeling and cave volume accuracy without the need for specialized equipment such as LiDAR or any substantial additional field work.