The standard cave survey technique is fiberglass tape measure, magnetic compass, and inclinometer, visually sighted point-to-point; passage width and height are

The standard cave survey technique is fiberglass tape measure, magnetic compass, and inclinometer, visually sighted point-to-point; passage width and height are recorded at each station in two planes, reflecting the traditional 2D cave map projections of plan and profile. These days, the most common mapping technique is a similar workflow, but with a ruggedized handheld laser distance meter with digital compass and inclinometer. They may have on-device storage, and they may transmit measurements to a PDA or tablet via Bluetooth. Some people sketch the 2D projections of the cave on that digital lineplot, some use the data to sketch with pencil on paper. A cave is a very hostile environment to electronics, so "caveman technology" is often intentionally preferred. Lidar and photogrammetry are quite difficult in a cave. The surfaces are irregular, of varying wet and muddy conditions whose reflectivity cause problems. And shadows - both visible and line-of-sight shadows - produce "swiss cheese" 3D models in all but the simplest caves. Lava tubes are often conducive to these techniques; their basalt composition wreaks havoc on magnetic compasses, so it's a welcome update. Having used a $75k FARO Lidar device in an admittedly clean and comfy cave before, I sure wouldn't attempt to haul it into the average "wild" cave for fear of trashing it. The promise of SLAM-based devices, a computationally-expensive technique for realtime integration of 3D data building a 3D model as you traverse the cave, is amazing; but the expense still high, the hardware still fragile, and caves are still irregular enough to never make this easy. Stone Aerospace in Texas has done some amazing work with autonomous underwater cave mapping using sonar. Their submersible robot has the same advantage that a quadcopter would have in an air-filled cave, whereas we human mappers are still stuck standing on (or crawling on) the floor.