Unfolding 3D Images of Underground Mining Tunnels

English Abstract:

Laser imaging of underground tunnels is increasingly used in mining engineering practice. Using the point cloud output of the laser sensor, a three-dimensional (3D) triangular mesh model can be generated. While laser technology has allowed the topology of rock faces to be captured in unprecedented details, 3D mesh models are typically very large and difficult to manipulate which makes the inspection of the results laborious.

We present two different methodologies which "unfold" a 3D mesh model of undeground mining tunnels so that it can be viewed as one connected two-dimensional (2D) drawing. We first examined traditional surface parameterization algorithms, which are often used by artists in computer graphics, to convert an artibary 3D mesh model into a 2D drawing. We found that while these methods were automatic and could provide 2D drawings which have minimal metric distortion (ie: ensuring that area and angles in 3D are conserved in 2D), they are generally not intuitive to interpret. We then explored mesh deformation methods, often used in computer animation, to reshape the 3D mesh to resemble a 3D plane before applying an orthographic projection to produce a 2D drawing. We found that while these methods required user interaction, and introduced a greater amount of metric distortion, they resulted in more intuitive 2D drawings.

To discuss the relative merit of these two methodologies, a large underground mining tunnel was imaged by a laser camera system and a 8.2m wide by 41m long by 6.7m high subsection was selected for analysis. The metric distortion produced by both methodologies was measured and will be presented along with the output 2D drawings.