LiDAR data was captured using a Riegl VZ-400 tripod mounted terrestrial laser scanner. Outside of the tube, the tripod was set up such that the scanner was between 1.5 and 2.5 m tall. Inside the tube the tripod was sometimes as short as 0.5 m. Geometric control was achieved using a pair of Trimble RB GPS antennae, one mounted on the LiDAR scanner (rover) and the other setup as a base station. In outside scans, before taking a LiDAR scan, the VZ-400 would use the GPSs to fix a real time kinematic (RTK) solution for the scanner’s location and then use that position (scan position) as a reference for LiDAR returns. Scan Positions were determined for in-tube scans (where GPS lock is not possible) in post processing by ensuring there was significant overlap between scans taken with GPS information and scans inside the mouth of a tube. Post processing was done using RIScan-Pro version 2 (scanner specific software). Also, in post-processing, overlapping areas of point clouds were merged and inaccuracies in roll, pitch and yaw, were resolved using a multi station adjustment routine and the data were projected in UTM coordinates.

All the Magnetic data collected at LBNM was collected using a Gem Systems GSM-19W magnetometer, mounted on an aluminum backpack frame at an elevation of ~2m, at a data point frequency of 2Hz.