Easy on-site volume calculation with point clouds! A new measurement method that requires no special equipment

Table of contents

• Traditional volume measurement methods and their challenges

• Basics of 3D surveying and point cloud data

• Methods for calculating volume using point cloud data

• Benefits of calculating volume with point clouds

• Use cases on construction sites

• Summary: Recommendation for simple surveying with LRTK

• FAQ

In construction and civil engineering sites, volume calculation (earthwork quantity estimation) associated with embankments and excavations is a crucial task for schedule and progress management. Traditionally, survey instruments were used to measure key points of the terrain, cross-sections were created, and volume was calculated using the average cross-section method. However, this approach requires time and manpower and is limited in accuracy because the number of measurable points is restricted. In recent years, 3D surveying using drone aerial imagery, terrestrial laser scanners, and even smartphones has been spreading, and it has become possible to calculate volumes more efficiently and accurately from detailed site geometry recorded as point cloud data. This article explains the basics of what point cloud data are, then describes the procedures and advantages of the new volume measurement method using point clouds. Finally, we introduce an easy surveying solution called LRTK that enables next-generation surveying with a smartphone without special equipment.

Traditional volume measurement methods and challenges

First, let's look back at the conventional volume measurement methods used on sites before point cloud technology emerged. Typical manual methods include the average cross-section method and the grid method. Surveyors measure heights at multiple points of embankments or excavation areas on site, create cross-sectional drawings or mesh elevation data, and calculate volume. For example, transverse surveys are conducted at regular intervals (e.g., 10 m (32.8 ft) intervals), the area of each cross-section is calculated, and the earthwork volume is estimated by multiplying the average area of adjacent cross-sections by the distance between them. Although this method has been widely used for many years, several issues have been pointed out.

First, there is the issue that the data are coarse and accuracy is limited. Manual surveying can only obtain a very limited number of points, so even for a large embankment, only a few height measurements are available. Because the overall shape must be inferred by connecting those sparse points, any unmeasured hollows or excesses in the unmeasured areas may be overlooked. In practice, a cross-section at key locations might match the design, but unexpected depressions or over-fill between sections could go unnoticed. Thus, the inability to capture surface and volumetric shapes in detail was a fundamental limitation of traditional methods.

Second, the work requires significant time and effort. Conventional methods require surveyors and technicians to visit the site in teams and set up equipment to measure point by point. On large sites, equipment must be repeatedly repositioned and re-leveled, resulting in enormous labor and time. After measurement, drawing and volume calculation remain, and sometimes confirming the as-built volume could take several days. During that time, work may have to be halted, resulting in inefficient situations such as “waiting several days to verify a difference of a few centimeters.”

Third, safety issues cannot be ignored. Traditional surveying often involved people walking on steep embankments or stretching tapes near operating heavy machinery, placing personnel at risk. Measurements at heights or on unstable footholds carry risks of falls or collapses, causing serious concerns for site managers.

As described above, conventional volume measurement had the problems of “few measurable points,” “high manpower and time requirements,” and “unavoidable hazardous work.” A new solution that addresses these issues is the measurement method using point clouds, described next.

Basics of 3D surveying and point cloud data

Now let’s confirm what the increasingly popular 3D surveying and point cloud data are. 3D surveying is a general term for techniques that measure site terrain and structures three-dimensionally and digitize them. Representative methods include terrestrial LiDAR scanning using dedicated laser scanners and photogrammetry, which reconstructs 3D models by processing multiple photos from drones or single-lens cameras. Laser scanners emit laser beams from the instrument and analyze their reflections to obtain coordinates for numerous surrounding points. A single scan can capture high-density point clouds with millions of points, enabling recording of terrain and structures in detail down to the millimeter level (0.04 in). Photogrammetry uses drone aerial photography or multiple ground photos processed by software to generate 3D point clouds or models of the target. Large surface areas can be photographed quickly, and advances in software have made it possible to create high-accuracy point cloud data easily in recent years.

Point cloud data obtained in this way are a collection of countless measured points in space, each with X, Y, Z coordinates (positional information) as 3D data. Points may also have attributes such as color (RGB values) or return intensity. Simply put, a point cloud is 3D model data represented by numerous points. While traditional surveying could obtain on the order of tens to hundreds of points, point cloud surveying can capture millions of points at once. Because the site geometry can be measured densely everywhere, fine undulations of the terrain and subtle surface details of structures can be reproduced accurately. For this reason, utilization of point cloud data is encouraged in construction industry DX efforts such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction, and the introduction of 3D surveying technologies is rapidly advancing.

Methods for calculating volume using point cloud data

So, how do you actually compute volumes from point cloud data? There are two major approaches. One is calculating fill and excavation volumes from differences between pre- and post-construction terrain data, and the other is calculating the volume of an individual stockpile or hole relative to a reference plane.

① Volume calculation by differencing pre- and post-construction point clouds: To accurately grasp the amount of fill or excavation generated by earthworks, it is effective to survey the terrain as point clouds before and after construction and compute the volume from the difference. Specifically, obtain point cloud data of the original ground before construction and point cloud data of the terrain after construction (after fill completion or after excavation), and align the two in the same reference coordinate system. By computing the height difference between the two point clouds in point cloud processing software, the volumes of cut and fill are automatically calculated. Because detailed data covering the entire site are compared, volume calculations that reflect subtle hollows and bumps are possible with high accuracy. Once point clouds are acquired, it is also easy to later extract arbitrary areas and perform additional volume calculations, enabling various quantity estimations as needed. For example, if heavy rain changes the terrain midwork, you can extract only the affected area from existing data and recalculate without re-measuring the entire site.

② Volume calculation of a single stockpile relative to a reference plane: When you want the volume of a single stockpile of excavated soil or piled materials, treat the surrounding ground as a reference plane. First, capture point cloud data covering the entire mound. In a point cloud viewer or analysis software, delineate the mound’s footprint (projected area) as a polygon and set a virtual horizontal reference plane (usually the average elevation of the surrounding ground). The software then automatically calculates the volume of parts protruding above the reference plane within the selected area. Conceptually, this is like numerically integrating the volume of a prism that encloses the mound from its base. Many software packages display the volume with one click after area selection and reference plane height are set. The same applies to excavated holes: specify the excavated region and calculate the volume of the portion missing below the reference plane (the removed soil).

With point cloud data, earthwork volume calculation can be greatly automated and simplified. However, to obtain highly accurate results, it is important to unify surveying references. For example, when comparing pre- and post-construction point clouds, they must be measured in the same coordinate system and with the same reference points to be aligned accurately. For drone photogrammetry, install known control points in advance; for laser scanners, perform proper instrument registration so that the two point clouds match without offset. Also, removing unnecessary point cloud data outside the calculation area beforehand reduces errors due to extraneous noise. Filter out unwanted objects such as machinery or people that appear in the data collection, and trim unrelated areas so calculations are performed on a clean dataset.

Benefits of calculating volume with point clouds

Using point cloud data for volume calculation offers many advantages over traditional manual methods. Here are the main benefits from the perspectives of accuracy, efficiency, and safety.

• Comprehensive measurement for improved accuracy: Point cloud surveying records the entire site as a high-density collection of points. Because it can measure details down to the millimeter level (0.04 in), volumes that were previously estimated from a few height points can now be accurately calculated from measured values everywhere. Comparing the design model (the 3D as-designed data) with the acquired point cloud allows evaluation of where fill is deficient or excessive across whole surfaces. Subtle depressions and bumps that manual surveys missed can be detected, dramatically improving as-built management accuracy. In many cases, earthwork quantities calculated from point clouds have been confirmed to be within about 1–2% error compared to conventional cross-section methods, demonstrating reliability comparable to traditional methods.

• Dramatic improvement in work efficiency: Another major benefit is the significant reduction in time and effort for surveying and calculation. Because point cloud technology measures the entire site at once, current condition point clouds for large development sites can be acquired by drone aerial photography in about half a day. Terrestrial laser scanning that used to take days can now be completed in hours. From the acquired point clouds, automatic volume calculation and cross-section generation are possible, greatly shortening manual drawing and computation processes. As a result, the number of days spent on as-built volume inspections is reduced, and results can be known on the same day without waiting for the surveying team’s report. In some cases, it is possible for one person to complete measurement and volume computation, which effectively addresses labor shortages. For example, a case reported that a task that previously required a team of four surveyors and one week (over 20 person-days) was completed by two people in one day (2 person-days) after switching to drone photogrammetry plus point cloud analysis—a roughly one-tenth burden in personnel and schedule. Such dramatic efficiency gains are achievable.

• Improved safety: Point cloud measurement is basically non-contact and remote, so surveyors need not enter hazardous areas. Cliffs, steep slopes, and deep excavations can be safely captured from a distance using drone aerial photography or long-range laser scanners. Scanning can be performed without interrupting heavy machinery, so it does not impede ongoing work. This reduces the risk of accidents during surveying and contributes to enhanced overall site safety management.

• Data reuse and visualization: Detailed 3D data acquired as point clouds are easy to store and share as digital records. Uploading to cloud services allows 3D inspection of remote sites from the office and smooth information sharing among stakeholders. Visualizing differences between point cloud data and design data as a heat map makes it possible to instantly see where fill is lacking or excessive. For example, color-coding design-conforming areas green, fill deficits blue, and overfills red helps visually confirm construction deviations. Systems can also automatically aggregate deficient and excess volumes and immediately provide concrete instructions like “how many cubic meters more soil are needed” or “where to cut how many cubic meters.” Acquired point cloud data can also be used for reanalysis and temporal comparison in the future. If you save the current condition data, you can compare it later when further excavation occurs to examine settlement or deformation—something impossible with paper drawings or photos. Being able to digitally archive the site “as-is” is a major advantage.

• Immediate results for rapid decision-making: With point cloud surveying and automatic analysis, you can obtain volume results the same day you measure, allowing immediate grasp of as-built quantities. This speeds on-site decision-making and enables quick optimization of construction operations. For example, if a person in charge measures daily excavation progress with point clouds and instantly calculates remaining spoil, they can quickly adjust dump truck orders or heavy equipment deployment for the next day. Decisions that previously required waiting for the surveying team’s report can now be completed on-site in real time. This immediacy shortens decision cycles and contributes to schedule reduction and cost savings.

As described, point cloud–based volume measurement outperforms traditional methods in terms of accuracy, efficiency, and safety. The Ministry of Land, Infrastructure, Transport and Tourism is promoting the use of 3D surveying technologies as part of ICT construction and i-Construction, and guidelines for as-built management using 3D measurement technology are being developed, including point cloud–based inspection methods. Adoption is already progressing on site, and volumes calculated from point clouds have been confirmed to have accuracy comparable to traditional methods. In other words, point cloud surveying offers both sufficient accuracy and overwhelming efficiency and safety benefits, and is beginning to become the new standard for volume calculation.

Use cases on construction sites

In what specific situations can point cloud–based volume measurement be used? In construction and civil engineering, accurate understanding of volume (earthwork quantities) is required in the following scenarios.

• As-built verification of earthworks: For roadworks and land development, it is necessary to verify that the embankment or cut meets the volume anticipated in the design or that the specified excavation quantity was removed. As-built inspections report volumes like “fill volume: ○○ cubic meters” and compare them with contract quantities. Calculating fill and excavation volumes by differencing pre- and post-construction point clouds provides objective proof of the site’s as-built condition.

• River and port dredging: For dredging work in riverbeds and ports, measuring how much sediment was removed is important. Direct measurement underwater is difficult, but methods that acquire pre- and post-dredging terrain point clouds using drone photogrammetry or shipboard laser scanning and compute differences are effective. This enables accurate measurement of dredged volumes for reporting to clients and as a basis for billing.

• Management of spoil and materials: Volume measurement is also useful for assessing stockpiles of spoil generated on site or piled materials (gravel, crushed stone). Measuring the volume of onsite piles helps estimate the number of dump truck loads required and supports inventory management. What used to be roughly estimated from visual inspection or a few height measurements can now be easily and accurately quantified by point cloud scanning, preventing unnecessary material loss and optimizing logistics.

Thus, the new point cloud–based measurement method demonstrates power across quality control, as-built management, and cost control on site. It is expected to be a foundational technology supporting on-site DX, and its use cases will likely continue to expand.

Summary: Recommendation for simple surveying with LRTK

Beyond volume measurement, RTK-capable point cloud scanning technology is transforming surveying and site management practices. The revolutionary approach of turning a smartphone into a surveying instrument symbolizes site DX. Democratizing as-built measurement—bringing it down from surveying specialists to something that anyone on site can do routinely—has major significance, directly strengthening quality control and productivity as a next-generation on-site tool.

In particular, smartphone + LRTK RTK point cloud scanning brings new value to site management through the freedom to “measure anytime, anywhere, alone.” There is no need to halt work for accuracy checks or perform risky manual surveys in hazardous locations, which accelerates the site PDCA cycle (plan, do, check, act). Fully utilizing the acquired 3D point cloud data for site visualization also yields secondary benefits such as early detection of previously unseen issues and smoother information sharing among stakeholders. Accurate positioning data supports rapid decision-making for safety management and environmental measures, contributing to a safer, more reliable construction system.

Given all these advantages, seeing is believing. Start by trying it in familiar, small-scale situations. Introducing LRTK for small embankment volume measurements or interim as-built checks will let you experience its ease and usefulness firsthand. Actively adopting new technologies will help your sites evolve to the next stage. LRTK, which enables “surveying with a smartphone,” has the potential to become a future standard surveying style. Take this opportunity to leverage state-of-the-art simple surveying tools and experience efficiency and sophistication in construction management tasks including volume measurement. You will likely see significant changes in workflows and enjoy major benefits in both outcome quality and productivity.

FAQ

Q. Can point cloud scanning really measure volumes accurately? A. Yes. With proper planning and execution, high-accuracy measurement is achievable. Point clouds obtained from the latest laser scanners and photogrammetry can secure accuracy within a few centimeters (within a few inches) by using known control points or network RTK corrections. Actual verifications report that volumes calculated from point clouds are almost equivalent to those by the conventional cross-section method (about 1–2% error). The accuracy meets the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management standards and is suitable for official inspections and quantity calculations. Nonetheless, to ensure accuracy, it is advisable to take basic measures such as installing control points and performing multiple measurements for checks.

Q. Can someone without specialist knowledge perform volume measurement with point clouds? A. Yes. Dedicated analysis software and cloud services can automatically perform tasks from point cloud alignment to volume calculation. Systems like LRTK are designed for non-surveying personnel, with simple operations that enable point cloud acquisition and volume calculation on a smartphone app with the push of a button. You don’t need to solve complex formulas yourself; understanding the basic procedure is enough to learn it through short training. Manufacturers and service providers also offer support and training materials, so questions can be quickly resolved.

Q. What equipment and preparation are needed to introduce point cloud scanning? A. It depends on the measurement method, but generally you need the measurement device itself and a positioning solution. For drone photogrammetry, this includes a drone and high-precision GPS, photogrammetry processing software, and, if necessary, ground control points. For terrestrial laser scanners, you need the laser scanner unit, dedicated software, tripods, and site reference targets. For smartphone surveying with LRTK, you can basically start with a LiDAR-equipped smartphone (e.g., iPhone or iPad Pro models) and a compact LRTK receiver. For higher-precision RTK positioning, subscribing to a GNSS correction service (network RTK Ntrip services, etc.) is required. This provides data to correct positioning errors via the Internet and is offered by national agencies, private providers, and mobile carriers. LRTK purchases often include guidance or trials for appropriate correction services. Once initial setup is complete, you simply power on at the site and start measuring, so the introduction barrier is greatly reduced compared to conventional methods.

Q. Can point cloud measurement be done where radio or GPS signals don’t reach? A. Even in GNSS-denied environments such as out of mobile coverage, indoors, or inside tunnels, there are ways to cope. One approach is combining terrestrial surveying instruments with known control points. For example, in a tunnel you can obtain control point coordinates near the entrance and use them as a start point, then connect point clouds generated by a laser scanner relative to that reference. Higher-end LRTK models also offer options that support Japan’s Quasi-Zenith Satellite System (QZSS) augmentation services such as CLAS, providing centimeter-level positioning augmentation (centimeter-level accuracy (half-inch accuracy)) so that correction information can be received directly from satellites even without mobile signals. If real-time corrections are difficult, post-processing methods like PPK (Post-Processed Kinematic) can achieve high accuracy without communications. Select the appropriate method for the site conditions to enjoy the benefits of point cloud surveying even in mountainous or underground areas.

Q. I’m worried about costs. Are there low-budget ways to start? A. High-end equipment can be costly, but there are increasingly low-cost entry options. For drone photogrammetry, you can start relatively cheaply with a commercially available drone and camera, and use cloud processing services that charge only when needed. Smartphone surveying with LRTK is also far less expensive than conventional large surveying instruments, as it combines a high-precision GNSS receiver with a smartphone. Because site staff can operate it without hiring a dedicated surveyor, the cost-performance is very high. For point cloud data processing, open-source free software and cloud services with pay-as-you-go models have emerged, greatly reducing software investment. With thoughtful choices, you can leverage point cloud technology on a limited budget and expand its use gradually from small sites while verifying benefits.