Long-distance SLAM scanning of mine tunnel - testing of precision and accuracy of Emesent Hovermap ST-X

underground environments, specifically within the Josef mine's main
gallery. The experiment aimed to evaluate the simultaneous
localization and mapping (SLAM) capabilities of the Hovermap STX over a 750-meter straight tunnel section where conventional
geodetic reference points are unavailable. To validate the scanner's
accuracy, reference measurements were obtained using a Leica
ScanStation P40 terrestrial laser scanner and a Leica MS60 total
station, establishing a millimeter-level geodetic network with
spherical control targets. The SLAM-based Hovermap ST-X scanner
captured point clouds in both single (1P) and double (2P) pass modes,
which were then analyzed for systematic errors in transverse (X),
longitudinal (Y), and vertical (Z) directions using RMSE metrics.
The study finds that while the Hovermap ST-X provides highprecision point clouds within shorter sections, cumulative errors arise
over the entire 750-meter distance, particularly in the longitudinal
axis, leading to slight compressions that necessitate scale corrections.
In the transverse direction, the deviations reach up to tens of
centimetres. The study also highlights that double-pass scans
effectively reduce transverse deviation errors compared to singlepass measurements, yet significant systematic errors persist in both
vertical and horizontal planes. These findings suggest that while
SLAM scanning offers rapid data acquisition and adequate accuracy
for various applications, its precision for geodetic surveys over
extended distances could be improved by integrating scaling
transformations and optimized pathing strategies. This work
demonstrates the SLAM scanner's utility in challenging underground
conditions and provides a framework for future precision
assessments in mine surveying. The results suggest practical
considerations for enhancing SLAM-based mapping accuracy in
geodetic applications, emphasizing the need for periodic control
points to minimize cumulative drift errors.