In construction sites and civil engineering works, volume calculations for excavations and embankments are needed on a daily basis. However, traditional manual volume measurements have been time- and labor-intensive, making frequent measurements difficult. In recent years, advances in high-precision positioning technologies—represented by GPS—and 3D technologies such as drones and photogrammetry have enabled automation of these volume calculations and dramatic efficiency gains. This article organizes why volume calculations are important on site, explains methods and benefits of volume estimation using the latest high-precision positioning × 3D technologies, and finally touches on LRTK, an easy surveying solution anyone can use, with points to consider when introducing it on site.

Table of Contents

• Why volume calculations are important

• Conventional volume measurement methods and challenges

• Advances and characteristics of high-precision positioning technologies

• Automating volume calculations using 3D measurement technologies

• Main benefits of high-precision 3D volume measurement

• Various use cases for volume calculations

• High-precision measurement anyone can do with LRTK simple surveying

• Conclusion

• Frequently Asked Questions (FAQ)

Why volume calculations are important

Volume calculations (earthwork volume calculations) are indispensable tasks in construction management and as-built management. Accurately understanding excavation and embankment volumes offers the following benefits:

• As-built management and quality assurance: You can verify whether the work has been carried out with the specified soil volumes and check for any excesses or shortages in the finished shape. If under- or over-filling/cutting is detected, corrective actions can be taken early.

• Quantity control and schedule management: By objectively quantifying daily progress (amount of work completed), you can continuously monitor whether the required earthwork quantities will be met within the project schedule. Disposal amounts for surplus soil and the ordering quantities for backfill materials can be properly planned based on quantities, preventing schedule delays and material shortages.

• Reporting and acceptance to the client: Upon completion, you can present volumes supported by measured data in as-built documents and quantity reports. Providing objective numbers rather than subjective estimates reduces discrepancies with clients and supervisory authorities and leads to smoother acceptance and settlement.

Thus, volume calculations are critical tasks that support site operations in terms of quality, cost, and reliability. However, accurately measuring soil volumes over large areas is not easy; traditionally this required large amounts of time and manpower through manual tasks such as setting out batter boards and creating cross-sections by surveyors. Recently, attention has focused on calculating volumes using point cloud data (three-dimensional survey data) obtained by drones and photogrammetry. If you create a 3D model (point cloud) from aerial photos or images taken with a smartphone, you can perform high-precision volume calculations in a short time based on high-density data of millions of points. What used to take several days to measure soil volumes can, in some cases, be completed in just a few hours to half a day including data processing. Of course, if 3D data are not properly corrected and processed, errors will occur, so appropriate georeferencing (coordinate alignment) using high-precision positioning is indispensable. From the next section, we will look at the key points of volume calculation using these new technologies.

Conventional volume measurement methods and challenges

First, let’s review how conventional volume measurements were carried out and what challenges existed. A representative conventional method is to use surveying instruments to measure control point elevations and cross-sectional shapes on site, compute cross-sectional areas on drawings, and calculate volumes using methods such as the average cross-section method. Specifically, transverse surveys are conducted at regular intervals, and earthwork volumes are calculated from the areas of the multiple cross-sections obtained. Although the theoretical precision of this method is high, accuracy is influenced by the spacing of survey points, so fine terrain undulations were often missed. Also, covering wide areas requires many survey points, and it was necessary for a skilled surveyor to set out batter boards and take measurements, making the process very time-consuming and labor-intensive. Therefore, frequent soil volume measurements during construction were practically difficult, and detailed surveys were often only performed just before as-built inspections.

Moreover, surveying work itself can be hazardous under certain site conditions. On steep embankments or in deep excavations, it is risky for workers to enter the area to take measurements, requiring safety measures and time. Thus, conventional volume measurement has long been constrained by being “time-consuming, unable to increase frequency, and having safety issues,” making efficiency improvements a long-standing challenge.

Advances and characteristics of high-precision positioning technologies

High-precision positioning technology has recently attracted attention as a key to solving these challenges. Ordinary GPS positioning has errors of several meters, but high-precision GNSS positioning methods such as real-time kinematic (RTK) enable positioning with errors on the order of centimeters (on the order of inches). RTK corrects errors using observations from a base station and a rover, but in Japan, centimeter-level positioning augmentation services provided by the Michibiki satellite (CLAS) and networked reference stations such as VRS are enabling centimeter-class positioning without installing a dedicated base station. In other words, today, with a compact GNSS receiver integrated with an antenna and a communications environment, anyone can obtain high-precision coordinates on site comparable to control surveys.

This advancement in high-precision positioning has also transformed surveying equipment. RTK surveys that formerly required a fixed base station plus a rover and wireless equipment can now be completed with palm-sized receivers and a smartphone. The realization of easy-to-use RTK operable with a smartphone, without expensive total stations or bulky GPS units, is revolutionary. The use of such high-precision positioning forms an important foundation for automating volume calculations.

Automating volume calculations using 3D measurement technologies

The other key, 3D measurement technology, has also developed and spread dramatically. Among them, photogrammetry reconstructs three-dimensional shapes of targets from many photographs taken by drones or smartphones. Dedicated software matches feature points between photos and computes camera positions and point coordinates, automatically generating detailed 3D point cloud models of the site without surveying. This enables high-density digital measurement of large areas in a short time.

By utilizing point cloud data obtained from photogrammetry or laser scanners, the volume calculation process itself can be greatly automated. What used to require measuring individual points on site and drafting drawings is now largely executed automatically by software on the point cloud. For example, overlaying the captured current-condition point cloud model with the design finish surface data allows software to immediately compute fill and cut volumes from the elevation differences between the two. Without much manual calculation or drawing work, the entire workflow from data processing to volume calculation can be completed in a one-stop fashion, achieving “automation of volume calculation.”

However, to use 3D point clouds accurately for earthwork volume calculations, ensuring positioning accuracy is critical. Models obtained from photogrammetry are initially in arbitrary scale and coordinate systems, and used as-is they will not match real-world dimensions. For example, if the entire model is offset by several meters (several ft) or has a slightly different scale, it cannot be used for correct volume calculations. Therefore, georeferencing the point cloud with measured coordinates using high-precision positioning is important. Specifically, photos captured by RTK-equipped drones are tagged with high-precision position metadata for each image, so the resulting point cloud automatically matches real coordinates after processing. Even with non-RTK drones, measuring a few ground control points (GCPs) with high-precision GNSS beforehand and using them to transform the point cloud model can ensure accuracy. In short, by combining 3D technologies with high-precision positioning, you can generate high-accuracy point cloud data aligned to site coordinates and automate volume calculations.

Main benefits of high-precision 3D volume measurement

Volume calculations using high-precision positioning × 3D technologies bring significant benefits to the field. Here are the main advantages:

• Substantial reduction in surveying time: What once took several days for wide-area soil measurements can, with drone surveys, be completed in about half a day including flight and automated processing. For example, as-built measurements for development sites of several hectares can yield results from a one-hour drone flight plus a few hours of processing, and some cases report 80–90% reduction in work time. Faster surveying accelerates the PDCA cycle of the whole project, enabling same-day condition assessment and reporting.

• Labor savings and mitigation of labor shortages: Point cloud measurements are performed automatically by camera-equipped devices, significantly reducing the personnel needed for surveying. Tasks that used to require a team of three can sometimes be done by a single drone operator. Allowing site staff to perform measurements without relying on highly skilled surveyors helps address chronic labor shortages.

• Improved safety: Because hazardous areas can be surveyed remotely, workers do not need to enter slopes or cliff edges. Drones can capture from the air, and ground-based LiDAR or long-rodded scanners can measure from a distance, reducing the risk of accidents during surveying. This also reduces the need for safety harnesses or access restrictions, benefiting overall safety management.

• Detailed and accurate data acquisition: 3D point clouds contain far more measured points than conventional surveying. They record subtle surface undulations and slopes, leading to improved accuracy in volume calculations. Locations that previously had only a few dozen measured points can yield millions of points with photogrammetry, resulting in more reliable as-built evaluations and quantity estimations.

• Advanced progress management: Faster measurement enables high-frequency volume surveys such as weekly or daily checks, making it practical to visualize progress quantitatively. This allows proactive management—detecting issues early and making course corrections. With up-to-date terrain data, features such as as-built heatmap displays and immediate computation of additional fill volumes speed up on-site decision-making.

In these ways, high-precision 3D volume measurement delivers “fast, safe, and accurate” surveying, dramatically improving productivity and quality control on construction sites.

Various use cases for volume calculations

High-precision point cloud volume calculations are beginning to be used in many site scenarios. Here are some representative cases:

• As-built management for large-scale development: For wide-area earthworks such as roads and residential development, drone photogrammetry is used regularly to monitor current soil volumes and verify conformity with the design. Rather than performing as-built measurements only at the end of construction, repeating them during various construction stages enables early corrections and adjustments to earthwork quantities.

• Management of fill and backfill material deliveries: On construction material yards and dam projects, measuring the volumes of stockpiles of fill and backfill materials helps with inventory control and confirms amounts moved in and out. Volumes previously estimated from visual inspection or number of dump trucks can now be measured accurately by drone aerial photography or ground-based laser scanning, enabling appropriate judgments about material surplus or shortage and reducing unnecessary transport costs.

• Estimating debris volumes at disaster sites: At natural disaster sites such as debris flows or landslides, drones are increasingly used immediately after an event to capture the current state and calculate volumes of displaced soil. Even in dangerous and inaccessible areas, aerial observation provides a comprehensive view and rapid estimates of collapsed material for restoration planning. Initial responses that once required time-consuming ground inspections are becoming much more efficient with data-centered analysis.

• Dredging works in rivers and harbors: For river and harbor dredging, underwater sediment volumes must be managed. Boat-mounted 3D scanners and acoustic sounding-derived point clouds are increasingly used to calculate dredged volumes. Combined with high-precision positioning, three-dimensional models of the seabed can be built and compared with planned dredge volumes to quantitatively manage dredging progress. This streamlines as-built verification and settlement tasks for dredging works.

In addition, high-precision 3D volume calculations are effective in many other scenes such as checking backfill volumes in bridge works and managing spoil removal from tunnels. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) is also promoting the use of 3D measurement technologies as part of ICT construction and i-Construction, and further adoption on sites is expected.

High-precision measurement anyone can do with LRTK simple surveying

A common concern when introducing the latest technologies is whether specialized knowledge or advanced equipment is required. However, simple surveying tools that anyone can use have emerged, enabling site technicians themselves to perform high-precision 3D surveys. A representative example is LRTK.

LRTK (Light RTK) is an all-in-one surveying device that combines a compact RTK-GNSS receiver with a smartphone. By attaching a receiver to a smartphone and receiving correction information in real time via a dedicated app, centimeter-level positioning can be achieved without complicated setup. The key feature is that RTK surveying, which used to be for specialists, has been made “portable and usable by anyone.” There is no need to set up a dedicated base station; with only a smartphone you can measure coordinates with accuracy comparable to expensive surveying equipment, making it truly a site-oriented simple surveying tool.

For example, products called LRTK Phone allow you to attach a receiver to an iPhone or other smartphone and walk the site to obtain point cloud data with absolute coordinates simultaneously with LiDAR scanning. Like recording a video, one person can walk around a large site and complete high-precision 3D surveying. The acquired point cloud is automatically uploaded to the cloud, where you can measure distances, areas, and volumes in a browser, or overlay design data to check as-built conditions. Thus, “survey with a smartphone → cloud-based analysis” is possible even without bulky equipment or advanced skills.

By using such simple surveying technologies, even small excavations equivalent to one piece of heavy equipment can readily adopt digital measurement. Situations that used to require waiting for a specialist survey team can be handled by the construction manager on site, eliminating waiting time and smoothing workflows. LRTK’s “RTK surveying anyone can use” is an innovative solution supporting DX (digital transformation) on construction sites.

Conclusion

Combining high-precision GNSS positioning with 3D point cloud technologies has made automation and efficiency gains in volume calculations a reality. What once required much time and manpower can now be performed quickly, with fewer people, and safely, while delivering far more detailed and accurate data. This not only raises on-site quality control standards but also directly improves overall operational productivity.

We have entered an era in which site technicians themselves can perform high-precision 3D surveys without relying on special large-scale equipment or artisanal skills. With a commercially available small drone and a palm-sized LRTK receiver, you can start as-built and earthwork quantity management using photogrammetry today. Introducing the latest technologies allows you to overcome the long-standing trade-off between accuracy and efficiency, elevating surveying work to the next dimension.

Start with small steps. Consider adopting these new measurement technologies in ways that suit your site. Accumulating these efforts will accelerate DX across the site and lead to building a safer and more resilient construction management system.

Frequently Asked Questions (FAQ)

Q: How much efficiency improvement can be expected in volume calculations compared to traditional methods? A: It depends on site scale, but significant time savings and labor reductions are possible. For example, earthwork measurements for a development site that took several days by ground surveying can be completed in about half a day using drone aerial photography and automated processing. There are cases where work time is reduced by about 80–90%, and required personnel is less than half of conventional levels. The ability to conduct frequent surveys enables highly efficient schedule management while maintaining high accuracy.

Q: What is high-precision positioning? How does it differ from ordinary GPS? A: High-precision positioning refers to technologies that apply real-time corrections to satellite positioning to improve location accuracy to the order of centimeters (on the order of inches). A representative method is RTK-GNSS, which combines observations from a base station and a rover to cancel error sources. Ordinary GPS positioning can have errors of several meters (several ft), whereas high-precision positioning can reduce this to a few centimeters (a few in). Previously specialized surveying equipment was required, but now small devices and communications make RTK positioning readily accessible. In short, it is useful to think of it as “ordinary GPS made orders of magnitude more precise.”

Q: Is the accuracy of volumes computed from 3D point cloud data reliable? A: If proper procedures for measurement and processing are followed, the accuracy of volume calculations can be equivalent to or better than conventional surveying. For photogrammetry, accuracy depends on image quality, shooting angles, and coordinate correction (GCP placement or RTK positioning), but under good conditions you can obtain point clouds with horizontal and vertical errors of a few centimeters (a few in). In such cases, volume-converted errors are minimal (well below a few percent). Conversely, poor image quality or lack of coordinate alignment can result in large errors. As a guideline, the lower bound of point cloud accuracy depends on the ground sampling distance of the original images (for example, if image ground resolution is 2 cm, you cannot expect accuracy better than that). The key is to adopt a shooting plan and correction methods that meet the required site accuracy; then practical accuracy for volume calculations is achievable.

Q: Can non-specialists use these systems? Can site staff handle it by themselves? A: Yes, modern measurement systems are designed to be user-friendly for site technicians. Features such as drone autopilot and photogrammetry software wizards allow beginners to obtain results by following procedures. While training and practice are desirable, the software handles complex surveying computations and equipment operations. Manuals and guidelines published by MLIT are also available, and by following procedures non-survey specialists can achieve high-precision results. Starting with expert support and gaining experience will enable site staff to operate smoothly on their own.

Q: Are there ways to calculate volumes without using drones? What about small sites? A: Even without drones, you can compute volumes using smartphones or handheld measuring devices. For example, taking 20–30 photos of a target (such as a soil mound) from various angles with a smartphone and processing them with photogrammetry software can yield an approximate 3D model. Volume can be calculated from elevation differences against a reference plane. Recent high-performance smartphones also include small LiDAR sensors that can capture point clouds with dedicated apps in real time. However, models made solely with a smartphone may have scale or height inaccuracies, so correcting at least one known measurement improves accuracy. For example, measuring a reference length or height with a laser distance meter or tape measure to scale the model, or measuring one control point with a simple GNSS device (such as LRTK) to set the vertical datum, will enhance precision. For small sites, familiar tools and free software can often suffice.

Q: What are the benefits of introducing LRTK? Is it easy for beginners to use? A: The benefits of adopting LRTK can be summarized as accuracy improvement, efficiency, and labor reduction. On the accuracy side, LRTK makes centimeter-class position information—previously obtainable only with expensive survey equipment—accessible to anyone on site. This improves as-built measurements and stakeout accuracy, reducing rework and improving construction quality. In terms of efficiency, tasks that previously required waiting for a survey team can be handled immediately by construction staff, reducing waiting time and scheduling losses; for example, you could “measure in the morning and prepare a report the same day.” Regarding labor reduction, one smartphone per person for surveying enables small teams to cover wide sites and measure on demand while multitasking, increasing flexibility in personnel allocation. LRTK is designed with a simple interface for first-time users, and the app guides operations so complex settings are unnecessary; manuals and support are also provided. True to its concept of “RTK anyone can use,” the barrier to on-site adoption is kept very low. For these reasons, LRTK is an attractive option for sites that want to renew surveying operations while balancing accuracy and efficiency.