Abstract.
Light detection and ranging (LiDAR) technology is finding new applications in various industries. Due to its high data accuracy, speed, and safety, LiDAR has found its application in construction. People often wonder why construction takes so long to complete. Using LiDAR in construction practices can improve design accuracy and efficiency, improve safety, and optimize construction project management. LiDAR provides detailed and accurate 3D models, allowing designers and builders to understand the terrain and existing structures better.
This white paper discusses using LiDAR in construction and how it complements the work process.
The sections reviewed are “Introduction to LiDAR,” “Construction Practices and its Technology,” “How LiDAR can help in Construction,” and “Using RESEPI in a Construction Site.” Finally, we will summarize the benefits of using LiDAR for construction.
Section 1. Introduction to LiDAR
Lidar (Light Detection and Ranging) emits laser pulses and measures the time they return after reflecting from objects. When a lidar emits a laser pulse, it moves at a constant speed of light. After a pulse hits an object, it reflects to the lidar. The lidar system records the time elapsed from when the pulse emits until it returns. Knowing the speed of light and the time it takes for the pulse to return, the lidar can accurately calculate the distance to an object. This process is repeated hundreds of thousands of times per second, allowing the lidar system to create detailed 3D point clouds of the surrounding space.
The main differences between different LiDAR models are in scanning angle, maximum scanning range, and scanning accuracy. Many modern LiDAR devices, such as the XT32, allow users to change rotation speed, scan angle, and number of returns. These parameters can be adjusted based on the user’s needs and affect cloud density, viewing angle, and the laser’s ability to penetrate obstacles such as trees and grass.
When the lidar integrates with an inertial navigation system (INS), such a device allows you to receive a cloud of points with the geographic coordinates of each point. Thus, all objects in the cloud will have their coordinates on the Earth’s surface. Each point ties to a coordinate accurate to the nearest centimeter [1]. An example of such an integrated device is Inertial Labs RESEPI Payload [2]. This payload is designed for use with drones or unmanned aircraft systems (UASs) but can also be used for vehicle-mounted or leg-mounted scanning. See Figure 1 for reference.
Figure 1. Inertial Labs RESEPI XT32 Payload with the camera.
The system is customizable for various applications, depending on the user’s wishes. It offers a LiDAR model, camera installation, and GNSS receiver. Thus, the user pays only for what they need.
Data collected by RESEPI Payloads are not usable without post-processing. The post-processing procedure uses the raw data and generates a highly accurate point cloud. For this purpose, Inertial Labs has developed specialized software PCMasterPro [3]. Software like RESEPI Payload helps users get started without prior preparation and with minimal manual intervention; all operations occur semi-automatically.
Section 2. Construction Practices and its Technology
The construction industry covers a wide range of work related to the construction of buildings and industrial facilities, from construction to decommissioning. Planning and design are the starting points of any construction practices, and these processes can accompany the facility from its construction to its commissioning.
Construction practices also include repair and maintenance work, any expansion or improvement of the facility, and demolition or dismantling.
Construction project management involves managing, regulating, and supervising a project from early development to completion. It aims to fully satisfy the client’s requirements for a viable project regarding functionality and budget.
The Construction Project Manager is responsible for planning, coordinating, budgeting, and monitoring projects from start to finish [4]. In other words, the construction project manager must organize:
- Budgeting and cost estimates
- Work schedules
- Construction method and strategy
- Consulting with clients
- Technical details with workers and specialists
- Personnel working on the construction site.
Completing these tasks requires competent planning, constant monitoring of the project’s status, the availability of necessary materials, and resolving issues that may arise between different construction team members.
Data collection and analysis play the most significant role here [5]. For example, at the initial planning stage, it is imperative to analyze the area where the client wants to start construction. Preparing the construction site is the most crucial stage since it will determine the effectiveness of all work conducted.
The most ideal option for construction is a flat plot with flat terrain. Uneven terrain, as well as an inconvenient shape of the plot, can significantly complicate the construction work and lead to additional waste of money. The building may sag or tilt if the area is swampy or groundwater is too close. If a river or lake flows near the construction site, this can lead to flooding during severe weather. In this case, you should consider the drainage system – this will protect you from unforeseen consequences during construction practices. Another critical stage in preparing the site for construction is the provision of infrastructure, i.e., the possibility of passage of large equipment and provision of coordination for the delivery of materials or waste removal in the event of building demolition [5].
Thus, all factors cannot always be considered with the naked eye, leading to increased costs for correcting errors. For example, vegetation on the territory allocated for a construction site can protect it from wind and sunlight. On the other hand, dense vegetation or tree roots can make construction difficult and, as a result, require increased costs and time to remove them.
It is essential to control the quality and speed of construction at the construction stage according to the schedules and drawings. Manual measurements take time and personnel, which leads to downtime and increased project deadlines. For example, when pouring a foundation, it is vital to accurately estimate the cement volume to avoid spending on unnecessary materials and prevent long-term storage. Which in turn will become an obstacle to planning at the construction site.
Several methods can be used when demolishing buildings, but explosives are the fastest and most economical [6]. Assessing the risks to surrounding structures and objects is essential, especially in urban environments. To do this, it is convenient to use a digital twin and simulate the consequences of the explosion and the possible scattering of fragments for effective demolition planning.
Thus, the project manager monitors and, depending on the information received, can redistribute tasks and effectively control the project construction process. Manual data collection takes time and effort, so next, we will look at how LiDAR can help collect data for effective project management and organization, as this is important for clients’, construction companies’, and investors’ budgets.
Section 3. How LiDAR Can Help in Construction
Before construction begins, you can fly a drone over the planned location to obtain a digital terrain map and estimate the surface slope to draw up an accurate budget for preparing the construction site. This model can identify land stability issues, including potential landslide risks and unsafe slope slopes (Figure 2).
Figure 2. Point cloud (left) and digital terrain model (right).
It can also assess site suitability based on various parameters, including vegetation, slope gradient, and existing structures, a crucial step in making informed decisions. Project managers can better plan budgets by estimating the number of tools, materials, and equipment needed in advance, reducing the risk of unexpected costs arising at later stages due to unfortunate planning.
Thanks to LiDAR, measuring the embankment’s volume or the trench’s depth is easy when pouring foundations or creating embankments. This will allow you to estimate the right amount of concrete and the required equipment to complete the work. Thus, it will enable you to effectively organize logistics so that construction materials are delivered on time and not stored on site, which can lead to logistics disruption at the construction site and increase construction time.
A drone must fly much faster than a manual analysis done directly on-site. Typically, the recommended drone speed for a LiDAR mission is 5 m/s. For the XT32, the recommended flight altitude is 50m for optimal accuracy and coverage (100x28m). Thus, it will take only 20 minutes to scan an area of 0.5 km^2. An example of a flight setup can be seen in Figure 3.
Figure 3. Inertial Labs RESEPI Payload installed on a drone.
LiDAR data will allow you to update information quickly and efficiently on the progress of construction practices. Thereby, managers, clients, architects, workers, and specialists will have an idea of the pace of construction and avoid misunderstandings between various parties. This will simplify the decision-making process and allow work to be conducted according to schedules and the allocated budget. Moreover, scans can happen daily to generate daily reports, which is essential for investors and the client, and inconsistencies can be identified and resolved early on, reducing the risk of costly future changes.
LiDAR scanners are a source of light used to measure space, making it possible to work both during daylight hours and at night.
LiDAR systems, such as RESEPI Payload, are equipped with a camera to obtain colored point clouds. Thus, the user can get a point cloud and images for photogrammetry in just one flight. The disadvantage of such a payload is its dependence on weather/lighting conditions.
In demolition projects, LiDAR data will help measure distances to adjacent structures and estimate the extent of demolition by quickly reproducing a digital twin from a point cloud.
To start using RESEPI PAYLOAD, the user will need a drone, flight license, RESEPI payload, base station, and a PCMasterPro software license for data processing [7].
Section 4. Using RESEPI in Construction Site.
Look at a real example of using RESEPI in constructing a road junction. Data was collected by flying over the construction site and then processed in PCMasterPro. The flight with processing took no more than an hour, after which the point cloud opened in Cloud Compare to calculate the spoil volume [8], Figure 4. As seen in the “Result” field, volume = 73.5 m3.
Figure 4. Spoil volume calculation in Cloud Compare.
Since the point cloud contains information about the coordinates of each point, the user can calculate the volume and height. Look at Figure 5, where two embankments are of different heights. As can be noticed, the parameter Zg is responsible for the height of the point; in the first case, it is equal to 613.6 m, and in the second case, it is 611.2 m. After spending just an hour flying and processing, the user can conclude that one of the spoils should be increased so that the heights are equal and more workers are sent to the desired point on the construction site.
And all this without using hand tools and wasting workers’ time on measurements; you do not have to leave your workplace. It is enough to configure the flight path once and launch the mission each time.
Figure 5. Spoil height.
RESEPI Payload uses the best components, the user receives highly accurate georeferenced data. Just look at Figure 6, which shows a cross-section of the point cloud. A thin line of dots is visible in places where the object is a plane.
Such scans can be conducted daily to track volumes and distances, which will help generate reports quickly, efficiently, and effectively manage the construction process, saving a lot of time.
Figure 6. Point cloud profile.
Conclusion.
The start of any construction requires many operations, both at the construction site preparation stage and throughout the entire time until the facility is decommissioned. Therefore, it is crucial to carefully plan all processes, from construction site preparation to waste removal and facility commissioning during construction.
Regular data collection using LiDAR will allow managers to effectively manage the construction practice process. Thanks to LiDAR, obtaining an accurate georeferenced digital map of the area on which construction work is planned to analyze its quality and topography is easy and quick. For example, the presence of slopes or holes will help more accurately allocate the budget for soil leveling and protect against sudden expenses in the future. During construction, point clouds will allow you to easily and quickly measure distances between objects with high accuracy, much faster than manual measurements. For example, when digging holes, trenches, or creating embankments in point clouds, third-party software can easily and quickly measure depth or height, thereby controlling the pace of construction and considering material costs.
For sites slated for demolition, LiDAR can help accurately measure the distance to nearby objects and determine the extent of demolition.
A demonstration of RESEPI Payload’s capabilities on a construction site shows the ease and speed of measuring the volume of essential objects, such as embankments, heights, and depths, at any point on the site.
LiDAR data will make meetings more effortless for the client, investors, and construction team. Workers and specialists will have an idea of the pace of construction and avoid misunderstandings between various parties. This will simplify the decision-making process and reduce the risks of unforeseen expenditure of funds and wasted time.
Inertial Labs is committed to providing high-quality solutions with customization and excellent value for money at an affordable price.
References.
[1] Wikipedia Contributors. “Inertial Navigation System.” Wikipedia, Wikimedia Foundation, 21 May 2019, en.wikipedia.org/wiki/Inertial_navigation_system.
[2] “RESEPI – LiDAR Payload & SLAM Solutions.” RESEPI, lidarpayload.com. Accessed 3 June 2024.
[3] Inertial Labs. “RESEPI Quick-Start Guide – Setting up Your LiDAR Survey System and PCMaster – Inertial Labs.” YouTube, 4 Aug. 2022, youtu.be/AygQTBVNrKw. Accessed 3 June 2024.
[4] CIOB. Code of Practice for Project Management for Construction and Development. 5th ed., Chichester, West Sussex. United Kingdom, John Wiley & Sons, Inc, 2014.
[5] Wikipedia Contributors. “Construction Management.” Wikipedia, Wikimedia Foundation, 5 Mar. 2019, en.wikipedia.org/wiki/Construction_management.
[6] Wikipedia Contributors. “Demolition.” Wikipedia, Wikimedia Foundation, 18 Sept. 2019, en.wikipedia.org/wiki/Demolition.
[7] “Buy Reach RS2+ | Buy Multi-Band RTK GNSS Receiver.” Emlid Store US, store.emlid.com/products/reach-rs2-plus?variant=47253689467185. Accessed 3 June 2024.
[8] “CloudCompare – Open Source Project.” Www.cloudcompare.org, www.cloudcompare.org/.