Photograph LIDAR Registration Methodology for Rock Discontinuity Measurement

Rock detachment events along roadways pose public safety concerns but can be predicted and safely handled using geological measurements of discontinuities. With modern sensing technology, these measurements can be taken on 3-D point clouds and 2-D optical images that provide a high level of structural accuracy and visual detail. Doing so allows engineers to obtain the needed data with relative ease while eliminating the biases and hazards inherent in taking manual measurements. This letter presents an approach for fusing the 2-D and 3-D data in natural and unstructured scenes. This includes a novel method for visualizing imagery obtained with very different sensors to maximize their visual similarity making registration a more tangible task. To show the effectiveness of our registration methodology, we evaluate measurements taken manually and digitally on rock facet and cut discontinuity orientations in Rolla, MO. Our method is able to align the 2-D and 3-D data with an accuracy of under 2 cm. The median difference between measurements manually obtained by a geological engineer and those obtained with our proposed software is 3.65.

I. Introduction

In mountainous and hilly regions, roadways commonly pass alongside tall walls of rocks. This poses many potential obstacles and dangers for drivers, road workers, and engineers who travel through these areas or who are responsible for building and maintaining the road infrastructure [1]. Discontinuities in the rocks, oftentimes, cause rock mass to break off along existing planar discontinuities that occur either naturally or as a result of engineered rock cutting during the road construction process [2]. Using analytical tools, the arrangement and orientations of single discontinuities or groups of discontinuities can actually be used to study rock stability and predict detachment events [2]. However, obtaining the measurements manually tends to be slow and cumbersome, and in some cases, dangerous because of potentially falling rock [3]. Due to time constraints and safety concerns, they are often only able to be employed in easily accessible locations, such as the base of a slope [4]. These types of restrictions can cause sampling biases and inaccuracies [5]. However, modern sensing technologies, such as photographs and light detection and ranging (LIDAR) laser scans, can be used to capture data more quickly and safely than traditional techniques [6]–[8].