A Laser Technique for Capturing Cross Sections in Dry and Underwater Caves

For the acquisition of 3D-geometry data of groundwater conduits in the coastal Karst plain of Yucatan near the town of Tulum a novel laser scanning device was developed and applied. The method is derived from similar industrial systems and for the first time adapted to the specific measurement conditions in underwater cave systems. The device projects a laser line over the whole cave perimeter at a certain position. This line represents the intersection of a plane with the caves wall. Through proper design and calibration of an imaging system it is possible to derive the true scale geometry of the perimeter by special image processing techniques. Through caption of regularly spaced images it is possible to reconstruct the true scale 3D-shape of a tunnel if position and attitude data is incorporated. The method provides easily operable acquisition of the 3D-data of caves in clear water with superior resolution and speed and facilitates the measurement in underwater tunnels as well as in dry tunnels significantly. The data gathered represent crucial input to the study of state, dynamics and genesis of a complex karst water regime.