Automated Method for Quantitative Measurement of Underground Construction Sites Using iPhone LiDAR Point Cloud Data
Authors: Mizutani Tsukasa , Iwai Shunsuke 
Published: November 2024

Electrical transmission methods vary globally between overhead and underground systems. Underground transmission is increasingly favored for several reasons, including landscape aesthetics, enhanced pedestrian safety, and disaster prevention. Overhead systems, while initially cheaper and easier to repair, pose substantial risks during disasters such as earthquakes, where utility poles may collapse, obstructing emergency response and increasing the likelihood of power outages. In contrast, underground systems mitigate these risks effectively.In regions with advanced pole-free electrification like Europe, utility infrastructure development predominantly favors underground installations to ensure both aesthetic and functional equality between gas and electrical systems. This approach has resulted in nearly complete underground utility coverage in major Western cities, contrasting sharply with Japan, where the transition from overhead to underground has been sluggish. This lag is due to post-WWII reconstruction policies which prioritized quick and stable overhead installations. Despite ongoing efforts, Japan's adoption of underground systems remains notably low.Globally, the construction of utility tunnels is promoted to optimize the use of underground space, particularly in urban centers where space is at a premium. These tunnels, housing essential services like electricity, water, and gas, are seen as a solution to urban underground congestion, a problem often referred to as the "Spaghetti problem." However, high costs and recent fiscal constraints have slowed the implementation of these systems in places like Japan.This research focuses on enhancing the construction efficiency of utility tunnels to expedite their adoption. This involves night-time construction operations including excavation, installation of conduits and "CC-Box" manholes, and subsequent backfilling. Such processes are labor-intensive and require pauses for measurement and documentation, making efficiency improvements critical.Our study leverages Light Detection and Ranging (LiDAR) technology to address these efficiency challenges. LiDAR point cloud data, employed in construction since 2004, has seen increased application following Apple's integration of LiDAR scanners in its 2020 iPad Pro and iPhone 12 Pro models. We aim to develop an algorithm to extract excavation sections from this data for precise volume measurements without reliance on Building Information Modeling (BIM).Our proposed method details techniques for measuring excavation dimensions (horizontal, vertical, and depth) at construction sites and discusses results from applying this method in field tests. These results indicate significant potential for enhancing measurement accuracy and reducing both labor costs and processing time. This research contributes to the field by providing a novel approach to utility tunnel excavation that utilizes advanced LiDAR technology for more efficient construction management and hazard prevention. The final sections of the paper summarize these findings and discuss their implications for future construction practices.