Underground oil shale mine surveying using handheld mobile laser scanners

The applicability of a handheld mobile laser scanner (MLS) in oil shale mine surveys and subsequent three-dimensional modelling of postextracted surfaces is assessed. Recommendations for optimizing the acquisition and processing of MLS data and visualization of the results are given. The resulting surface geometry accuracy is validated via terrestrial laser scanner (TLS) reference data. Typical discrepancies between TLS and MLS data points remain within 2 and 5 cm in horizontal and vertical directions, respectively. The area of pillars and volumes of the extracted material are estimated by data analysis. The results are compared with those of the conventional mining survey. The detected discrepancies evidence that the laser scanning results provide a realistic outcome due to the evenly and densely spaced points within the point cloud. The result discrepancies between the tested surveying technologies are small and fully satisfy contemporary accuracy requirements. However, the handheld mobile laser scanning appears to be the most suitable method for underground mining surveys. The survey results enable reduction of mining losses and improvementt of the design of mining geometry.