Dramatic Efficiency Gains in As-Built Volume Measurement! 3 Cutting-Edge Technologies Including Cloud Utilization

Table of Contents

• What is as-built volume measurement? Its importance and challenges

• Data sharing and automated analysis using the cloud

• Rapid 3D measurement with drone photogrammetry

• Easy point cloud acquisition with 3D laser scanning (smartphone use)

• Simple high-precision surveying enabled by LRTK

• FAQ

What is as-built volume measurement? Its importance and challenges

"As-built volume measurement" is the process of measuring and verifying whether the volumes of earthworks—such as fills and excavations—on completed civil or construction works have been placed or removed according to design. For example, in roadworks or land development, it is necessary to accurately determine whether the volume of filled soil has reached the specified quantity and whether the excavated material has been properly removed. As-built volumes are a crucial indicator directly tied to construction progress (work quantity) management, pass/fail judgments during inspections, and even the calculation of contract payments; the measurement accuracy therefore affects the fairness and economics of a project.

Traditionally, as-built volume measurement has been performed mainly by manual methods. Common approaches included surveying the ground before and after work to calculate fill and excavation volumes from differences in the terrain, or manually computing volumes using average cross-section methods based on design cross-sections. However, methods that measure only a limited number of points inevitably have precision limits and tend to accumulate errors or omissions in unmeasured areas. Even if heights are checked at a few points across a large site, there is a risk of overlooking small bumps, excess fill, or unremoved soil between those points. In addition, manual measurements using tape measures or leveling rods often require multiple people, and the process from measuring and recording to calculation and drafting consumed significant effort and time. Because volume calculations were done after returning to the office with the collected data, it was not possible to determine on-site whether as-built quantities were sufficient or excessive, which often resulted in inefficient rework discovered later. Transcribing notes into field books and re-entering data in the office also carried the risk of human error. In this way, traditional as-built volume measurement demanded substantial labor and time yet lacked comprehensiveness and immediacy, placing a heavy burden on site personnel.

In recent years, digitalization (DX) of surveying and construction has rapidly advanced to address these issues. The Ministry of Land, Infrastructure, Transport and Tourism has been promoting the on-site introduction of ICT and 3D surveying through "i-Construction," and revisions to the As-Built Management Guidelines have newly incorporated surface-based as-built management using point cloud data, driving industrywide efficiency improvements. In practice, multi-point measurement technologies such as drone photogrammetry and 3D laser scanning allow high-density capture of as-built conditions across entire sites that previously could be measured only in part, enabling advanced quality control such as intuitively grasping variability in fill thickness or surface irregularities via heatmap displays. For example, where a 500 m (1640.4 ft) long slope was once evaluated by measuring points every 20 m (65.6 ft), 3D measurement can densely scan the entire 500 m (1640.4 ft) area and detect differences from design without omission. As-built volume measurement is thus shifting from "manually measuring small areas little by little" to "collecting digital data for the entire site at once and performing automated analysis."

Now, let’s introduce three specific cutting-edge technologies that dramatically improve the efficiency of as-built volume measurement.

Data sharing and automated analysis using the cloud

First to note is the use of the cloud. If as-built data acquired by surveying instruments or smartphones (such as measured point coordinates, photos, or point cloud models) are uploaded to the cloud immediately, automated analysis and data sharing can be performed while still on site. For example, in excavation work, simply overlaying point cloud data of the terrain acquired before and after work on the cloud allows removal volumes (excavation volumes) to be calculated from the differences in an instant. Traditionally, volume calculations were performed after taking data back to the office, so it was not possible to immediately assess on-site whether as-built quantities were short or surplus. With cloud analysis, volume calculation can be completed in just a few minutes to tens of minutes, and the results can be shared with stakeholders on site.

By uploading data to the cloud, supervisors in the office or clients can also check the latest as-built data via a web browser. Site personnel no longer need to bring data back on USB sticks or send files by email—everyone can view the same 3D model or measurement report on the cloud. This reduces rework due to misunderstandings and shortens decision-making time. If analysis results are shared via screen sharing, remote meetings and explanations to clients can proceed smoothly.

The cloud is not just storage; it also functions as a high-performance compute engine. Tasks such as generating 3D models from photogrammetry or automatically comparing point cloud data with design drawings can be executed quickly on cloud servers. Without installing specialized software on local PCs or purchasing expensive hardware, you can access advanced analysis features over the Internet. Because the cloud automatically organizes and analyzes the large volumes of data collected on site, personnel can devote more time to higher-value tasks such as decision-making and countermeasure planning. Cloud utilization is a key factor that transforms the entire workflow of as-built volume measurement and dramatically improves efficiency and accuracy.

Furthermore, 3D data accumulated on the cloud remain as digital as-built records after project completion. Revisiting past as-built data can make it possible to understand and verify the state of the site in detail during later renovations or in the event of problems.

Rapid 3D measurement with drone photogrammetry

Next, drone (unmanned aerial vehicle) photogrammetry is revolutionizing as-built volume measurement. By automatically photographing the entire site from above with a camera mounted on a drone and generating a 3D model of the terrain (point cloud data or digital terrain model) from the set of images, you can grasp the as-built conditions of large areas in a short time. For example, a development site of tens of hectares that once required surveyors days to measure manually can be photographed by drone in roughly half a day, and processing the acquired data with dedicated software yields high-density 3D survey results.

The biggest advantages of drone photogrammetry are the overwhelming reduction in working time and wide coverage. If a drone performs aerial photography according to an automated flight plan, it can capture data from steep slopes or dangerous locations where people cannot safely enter. By generating point clouds and orthophotos from many images taken at ground-level resolutions of a few centimeters, you will not miss subtle surface undulations or remaining soil. Compared with conventional ground surveys that measured points every few meters, drone surveys record the site shape at an immensely higher point density, improving the precision and reliability of volume calculations.

Recently, surveying drones equipped with RTK-GNSS have become more common. Conventional photogrammetry required installing multiple ground control points (known coordinates) beforehand for accuracy, but RTK-equipped drones perform real-time high-precision position correction during flight, eliminating the need for large-scale control point work. This further shortens preparation time from arrival at the site to data acquisition and enables even faster volume measurement. Post-flight data processing is also increasingly automated by cloud services and AI, so software can create appropriate 3D models without specialized expertise.

With the introduction of drone surveying, the work of calculating fill and excavation volumes has been dramatically streamlined. Computers automatically calculate volumes from large point cloud datasets, leaving humans to simply review results and make judgments. The ability to quickly, accurately, and comprehensively determine earthwork volumes accelerates the site PDCA cycle, reduces rework, and improves cost control. It also contributes to improved safety by reducing the need for personnel to walk around on the ground.

Easy point cloud acquisition with 3D laser scanning (smartphone use)

The third topic is 3D laser scanning technology. Traditionally, terrestrial 3D laser scanners (TLS) could acquire high-precision point cloud data, but the equipment was costly and specialized, limiting use to some large-scale sites. However, recent technological advances have made laser scanners smaller and less expensive, and LiDAR sensors built into smartphones now allow easy 3D scanning. For example, using the LiDAR function on an iPhone, you can instantly generate a point cloud of surrounding structures and terrain within roughly 5 m (16.4 ft), obtaining highly detailed data that effectively copies the site. Simply walking around the object to be measured records its shape as a surface, dramatically improving efficiency compared with measuring each location with a tape measure.

For wide areas that smartphone LiDAR cannot cover, photogrammetry using the smartphone camera can complement it. Using a dedicated app to photograph the site and performing image analysis in the cloud to generate a 3D model makes it possible to capture point clouds in narrow areas inaccessible to heavy machinery or along long structures. This mobile-device-based 3D measurement lowers the bar for as-built management that previously required dedicated surveying teams, enabling site supervisors themselves to perform measurements. In fact, there are reports of earthwork sites where a single person completed scanning roughly 8000 cubic meters of fill in about half a day using smartphone measurement, then immediately shared the acquired point cloud via cloud services and began creating as-built drawings.

Importantly, measurement methods using familiar devices such as smartphones have begun to gain official recognition. The 2022 revision of the Ministry of Land, Infrastructure, Transport and Tourism’s As-Built Management Guidelines officially added the use of simple mobile devices such as smartphones as acceptable measurement instruments for public works. In other words, even small- to medium-scale sites can undertake 3D as-built measurement using smartphones without owning expensive surveying equipment. The affordability and portability of smartphone measurement are a major boon for the construction industry, which faces chronic labor shortages and a decline in skilled technicians. Smartphone 3D scanning is intuitive enough for non-specialist site staff to use and enables immediate measurement when needed, making it a game-changer that raises on-site as-built volume measurement capabilities.

Simple high-precision surveying enabled by LRTK

The final technology to introduce is LRTK, a groundbreaking solution that combines the above technologies to enable "anyone, anywhere, anytime" as-built surveying. LRTK (short for LRTK) is a surveying system consisting of an ultra-compact RTK-GNSS receiver that attaches to a smartphone and a dedicated app, turning an ordinary smartphone into a surveying instrument with centimeter-level accuracy (half-inch accuracy). Conventional high-precision GNSS surveying (RTK surveying) required fixed base stations and expensive dedicated equipment, but with LRTK you only attach a compact device that integrates the antenna and battery to your smartphone. It supports Japan’s satellite positioning service (Michibiki’s CLAS) and network RTK, and can provide stable positioning errors within a few centimeters even in mountainous areas outside of communication coverage.

The LRTK app is intuitive and simple to operate. Point the smartphone (with the antenna attached) at the point to be measured and tap a button to instantly record the latitude, longitude, and height of that location. The measurement point name, date and time, and GNSS reception status are saved automatically, and conversion to the site’s plane rectangular coordinate system as well as geoid height correction calculations are performed in real time. In other words, there is no need to copy numbers into a field notebook, and you can complete the workflow with just a smartphone without carrying paper drawings or calculators. Users at sites that have adopted LRTK report that "writing instruments on site are no longer needed" and "inexperienced staff can become immediately productive," dramatically simplifying the once-tedious as-built measurement tasks.

LRTK also offers precision comparable to first-class surveying instruments. Standalone positioning errors are on the order of a few centimeters, but by averaging multiple measurements you can improve accuracy to horizontal-level precision of a few millimeters. In actual validation, there have been cases where LRTK positioning results differed from first-class GNSS surveying instruments by less than 5 mm (0.20 in), demonstrating near-professional equipment accuracy. It has been confirmed that LRTK can handle management items with allowable errors on the order of about 5–50 mm (0.20–1.97 in). In addition, positioning data, photos, and point cloud data obtained by LRTK can be linked to the cloud with one touch, so office staff can check results or compare with 3D models immediately after measurements are taken on site. Eliminating data handover time lags speeds up pre-inspection preparation and report creation.

By leveraging LRTK, high-precision as-built volume measurement can be achieved even by non-experts. LRTK, which fully utilizes smartphones and the cloud, enables rapid as-built management on small teams and is a trump card for dramatically improving surveying productivity. Wider adoption of such digital technologies is expected to accelerate DX across construction sites beyond just as-built volume measurement. If you feel challenged by inefficiencies in as-built measurement, consider exploring cutting-edge solutions such as LRTK.

FAQ

Q: What is as-built volume measurement? A: It is the process of measuring the actual volumes of fills and excavations in civil works and confirming whether they match the design quantities. It is performed as part of as-built management and serves as the basis for pass/fail judgments, progress (work quantity) management, and calculation of contract payments.

Q: What challenges exist with traditional as-built volume measurement? A: Traditionally, measurements were made at limited points using tape measures, leveling rods, or total stations, and volumes were manually calculated based on drawings. This required significant time and manpower and risked overlooking gaps, surface irregularities, or remaining soil. Results could not be confirmed immediately on site, leading to rework discovered later. Human errors such as transcription mistakes in field notebooks or calculation errors could also occur, creating quality risks.

Q: What is point cloud data? A: Point cloud data are collections of innumerable 3D coordinate points obtained by laser scanners or photogrammetry. Each point contains XYZ coordinates (and sometimes color) information, allowing high-fidelity recording of site geometry. By analyzing point clouds, you can calculate surface undulations and volumes or visualize deviations from design models, making them useful for as-built management and quality inspections.

Q: What are the benefits of using drones? A: Drone photogrammetry allows rapid and comprehensive measurement of wide areas. Drones can capture locations inaccessible to people, and produce far denser point cloud data than ground surveys, improving the accuracy of volume calculations and greatly reducing work time. It also enhances safety by reducing the need for personnel to walk on site.

Q: Can smartphones really perform accurate surveying? A: Yes—using the latest smartphone surveying technologies, it is possible. For example, attaching a small RTK-GNSS receiver to a smartphone can achieve positioning accuracy on the order of a few centimeters. In fact, the Ministry of Land, Infrastructure, Transport and Tourism formally acknowledged smartphone surveying in the 2022 revision of the As-Built Management Guidelines, recognizing its accuracy and usefulness.

Q: What are the advantages of using cloud services? A: The cloud enables immediate analysis and sharing of data collected on site. Uploading surveying data automates tasks such as point cloud comparison and volume calculation, and allows real-time sharing of results with remote stakeholders. High-performance PCs and specialized software are no longer required for data processing, reducing downstream effort for report preparation.

Q: What is LRTK? A: LRTK is a smartphone surveying system consisting of a small RTK-GNSS antenna that attaches to a smartphone and a surveying app. It turns a smartphone into a centimeter-level accuracy (half-inch accuracy) surveying instrument capable of point cloud scanning and photogrammetry. Acquired data can be automatically saved and analyzed in the cloud, enabling anyone to perform high-precision as-built volume measurement without specialized equipment.