Table of Contents

• Background: why volume calculation is required on site

• Traditional earthwork measurement methods and their challenges

• A new tool that can calculate volumes with a smartphone

• Major improvements in construction efficiency through earthwork management

• Achieving cost reduction through earthwork management

• Simple surveying with LRTK

• FAQ

Background: why volume calculation is required on site

On civil engineering sites, land development projects, and disaster recovery sites, there is a strong demand to be able to immediately calculate the volume of excavated or filled soil on site. If accurate earthwork volumes can be grasped instantly on site, process management and cost control become markedly more efficient. Until now, volume estimation often relied on experience and intuition, and when those estimates were off it led to unnecessary rework and increased costs. Being able to perform accurate volume calculations on site immediately is an indispensable factor for smooth construction progress and appropriate decision-making.

In recent years, the construction industry has faced severe labor shortages and a need for work-style reform, increasing demand for more efficient construction management methods. In addition, initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism-led *i-Construction* are driving the digitalization (site DX) of construction sites. This has heightened the need to streamline surveying tasks that used to require significant time and effort by using digital technologies. Against this backdrop, there has been growing anticipation for volume-calculation tools that site staff can easily use themselves and obtain immediate results on site.

Traditional earthwork measurement methods and their challenges

A variety of methods have been used to calculate and manage earthwork volumes on site. However, each method has its own issues, making real-time and easy measurement challenging. The main traditional earthwork measurement methods and their problems are as follows.

• Precision surveying and manual calculations by surveyors: Surveyors measure numerous points using a total station (TS) or level and calculate volumes using methods such as the average cross-section method. While highly accurate, this requires considerable time and effort and specialist knowledge. It is not realistic to call in experts to perform detailed measurements every time on busy sites. Also, because there is a time lag from measurement to office calculation and drawing creation, obtaining results on the spot is difficult.

• Rough estimates from equipment counts or truck numbers: A simple method estimates volume from dump truck capacity and number of trips or from the number of bucket cycles of an excavator. However, accuracy is lacking and the discrepancy with actual volume can be large. These are only rough guides, and large errors can later cause disputes due to quantity mismatches.

• Judgments based on experience or visual estimation: Sometimes veteran equipment operators or site supervisors estimate volumes as “about X trucks’ worth” based on feel. Human perception-based judgments are uncertain and can cause problems in reporting to clients or during progress-based settlements. Estimates based on experience can undermine the accuracy of construction planning.

• Drone aerial photography (photogrammetry): A now-common method is to capture the site from above with a drone and use photogrammetry software to create 3D models or contour maps to compute volumes. While it can survey large areas in a short time, drawbacks include the need for flight permission applications and specialized operators, and the image processing requires time and skill. It is also weather-dependent and not suited to “immediate on-the-spot” needs. If frequent progress measurements are desired, drones have limits on measurement frequency.

• 3D laser scanners: Ground-based high-precision laser scanners can acquire point cloud data from which volumes are calculated. This yields very precise results but the equipment is expensive and difficult to operate, requiring specialist technicians. Even when a single device is shared across multiple sites, arranging and transporting it is cumbersome, and data processing is heavy, so it is not something anyone on site can easily use.

As shown, traditional methods had challenges in “ease of use,” “immediacy,” and “versatility.” Even with the latest measuring equipment installed, sites sometimes could not make practical use of it, and the time-consuming processing left it underutilized. What had long been sought was a means that allows anyone on a busy site to quickly measure earthwork volumes without special effort.

A new tool that can calculate volumes with a smartphone

To meet these needs, a new tool has recently emerged that allows volume measurement with a smartphone. By utilizing the camera and sensors built into a handheld smartphone and scanning the terrain or embankment while walking the site, detailed 3D data (point cloud) can be acquired in a short time. Without special surveying equipment, the familiar smartphone transforms into a 3D measuring device.

For example, some of the latest high-performance smartphones are equipped with small LiDAR sensors, which can measure distances to surrounding terrain and structures in real time. Combined with photogrammetry technology that analyzes multiple images taken by the smartphone camera, larger areas can also be converted into 3D point clouds and recorded in detail. These technologies have made 3D surveying—formerly requiring specialized equipment—possible with just a smartphone.

Particularly noteworthy is solutions that combine a smartphone with a high-precision GNSS receiver. Built-in GPS in smartphones used to provide positioning accuracy on the order of several meters, but by attaching a dedicated GNSS receiver that supports RTK (Real Time Kinematic) to a smartphone, satellite positioning accuracy can be dramatically improved. Using RTK-GNSS to incorporate correction information in real time can reduce horizontal and vertical errors to a few centimeters (a few inches), allowing high-precision position information to be directly attached to point cloud data acquired with a smartphone. In other words, not only shapes but also positions can be measured accurately in 3D, enabling immediate acquisition of reliable earthwork volume data aligned with site coordinate systems.

Thanks to the combination of smartphone plus high-precision GNSS, even non-specialists are increasingly able to perform high-precision point cloud surveying with the push of a button. The emergence of new tools that allow anyone on site to intuitively perform 3D measurement and volume calculation is beginning to greatly change earthwork management.

Major improvements in construction efficiency through earthwork management

Adopting new digital earthwork management methods can dramatically improve on-site construction efficiency. The concrete benefits include the following.

• Immediate data acquisition and decision-making: You can measure earthwork on site whenever needed and get results on the spot, greatly reducing waiting time. There is no need to interrupt work to obtain survey results or wait for later reports; decisions can be made in real time. For example, questions like “How many more cubic meters of fill are needed?” can be answered instantly, making it easy to adjust construction schedules.

• Reduced dependence on specialist staff: With simple smartphone-based surveying, site supervisors or workers themselves can perform necessary measurements without a specially qualified surveyor. This eliminates the time spent arranging for specialists and allows prompt verification of as-built conditions using on-site personnel. Even with labor shortages, limited staff can efficiently manage progress.

• Detailed control through repeated measurements: Because measurements are easy to perform, volumes can be measured as often as needed—even daily. Subtle changes and day-to-day progress that were previously difficult to capture can now be quantified. Early detection and quick correction of small discrepancies prevent large-scale rework and ultimately shorten the construction period.

• Faster decision-making through data sharing: Digital earthwork data can be displayed on a tablet or smartphone as a 3D model on site and shared immediately with relevant parties inside and outside the company via the cloud. The site representative can explain the latest situation to remote managers or clients without having to return to the office to write reports. Meetings using shared digital materials reduce misunderstandings and improve communication efficiency.

In these ways, digitizing and real-timing earthwork management on site brings efficiency to all aspects of construction. It will be a major help to construction managers who run sites with limited time and personnel.

Achieving cost reduction through earthwork management

Digital earthwork management also delivers significant cost benefits. By accurately knowing volumes at the right time, the following cost reductions can be expected.

• Elimination of wasteful work and materials: Accurate volume control prevents mistakes such as “excavating more than necessary” or “insufficient fill requiring additional material procurement.” Reduced excess excavation and unnecessary backfilling cut wasted equipment operating time and labor costs. Appropriate adjustment of material orders also reduces unnecessary material purchase costs and disposal costs for surplus soil.

• Optimization of transport and disposal costs: Knowing the exact amount of spoil to be hauled off or backfill to be brought in allows optimization of the number of dump trucks and trips. For example, quantitatively planning “how many more truckloads to remove the remaining spoil” or “how many more cubic meters of fill are needed” prevents costs from truck shortages/overages such as waiting time or additional arrangements. Disposal costs for soil can be estimated and negotiated based on accurate quantities, avoiding cost overruns due to over-ordering by guesswork.

• Clearer progress-based settlements: During construction, disagreements with clients over quantities at progress reporting or settlement can arise. Objective, digitally measured volume data provides clear grounds for explanation to clients, preventing unnecessary reductions or disputes. Transparent quantity management builds trust and helps avoid future needless costs (such as dispute-handling costs).

• Reduction of survey and investigation costs: Traditionally, contractor surveys by specialists incurred substantial costs. Using the latest simple surveying tools on site can reduce outsourcing and labor costs for surveying. Being able to measure in-house when needed compresses expenses previously paid to external surveyors, resulting in overall significant cost reductions. Digitalization also reduces costs and time associated with paper drawings and document creation.

Thus, streamlining earthwork management on site directly contributes to cost optimization. Eliminating waste and managing quantities accurately helps improve the project’s overall financial outcome.

Simple surveying with LRTK

One example of an innovative “smartphone + GNSS” earthwork measurement tool is simple surveying using LRTK. LRTK is a smartphone-integrated high-precision GNSS surveying system developed by Refixia Co., Ltd. It is used by attaching a small receiver to a handheld *iPhone* or *Android* smartphone. With the dedicated LRTK app you can perform 3D scanning and positioning on site and directly calculate the volumes of fills and excavations from the acquired point cloud data. It also integrates with cloud services, allowing you to immediately upload measured data to the cloud for internal sharing or perform detailed analyses in the cloud as needed.

LRTK is designed to be simple to operate so that first-time users can handle it intuitively. The smartphone interface is displayed in Japanese and easy to read, and guide messages are shown for each surveying mode, so even those who are not comfortable with machinery can proceed with measurements with confidence. You can acquire point clouds of wide areas in a few minutes after starting a 3D scan, and if synchronized with the cloud you can get volume calculation results immediately. It can be mastered in a short time without specialist knowledge, and if you encounter problems on site you can share LRTK cloud data with headquarters or remote technicians for advice. With an established support system, even sites new to digital surveying can introduce it with confidence.

If you are thinking “I want to quickly perform volume calculations on site,” smartphone-based simple surveying with LRTK is a promising option. By using this cutting-edge tool that solves conventional problems and simultaneously achieves major improvements in construction efficiency and cost reduction, you can take your site to the next stage.

FAQ

Q: How accurate can volume calculations performed on site with a smartphone be? A: By combining a smartphone with a high-precision GNSS (RTK method) receiver, measurements can be kept within a few centimeters (a few inches) of error in both horizontal and vertical directions. This level of accuracy is sufficient for typical civil engineering as-built management and volume calculations and can produce data that meets public works as-built measurement standards. Accuracy is dramatically improved compared with traditional manual estimates.

Q: Can it be used without special surveying knowledge or qualifications? A: Yes, it is designed so anyone can use it. Smartphone-based measurement apps have intuitive user interfaces, and complex equipment settings and calculation processes are automated. Therefore, people without surveying experience can easily perform volume measurements. In practice, many sites report that after a short operational briefing, site staff can start using the system immediately and operate it without issues even without specialist technicians present.

Q: How long does the measurement work and volume calculation take? A: It depends on the scale of the target, but for example, for a fill several meters high and an area roughly 30 m (98.4 ft) square, walking around the area with a smartphone will complete the point cloud scan in a few minutes. Volume calculation from the point cloud is automatically processed in the cloud, so the overall work time is about 10 minutes to obtain results. Tasks that used to take half a day to a full day with manual surveying can be completed in a short time.

Q: Is digital measurement possible at sites without an internet connection? A: Basic measurements are possible even offline. For example, LRTK can use augmentation signals from Japan’s quasi-zenith satellite “Michibiki,” so high-precision positioning can be performed even at mountainous sites or inside tunnels where mobile signals do not reach. Point cloud data can be synchronized to the cloud after moving to an area with reception; you can also temporarily store data on the smartphone and upload it later. Measurements can continue even when the site lacks internet connectivity.

Q: Compared with drone photogrammetry, what advantages does smartphone-based earthwork measurement have? A: Drone aerial surveys have the advantage of measuring wide areas at once, but they are constrained by flight restrictions, weather, and the need for piloting and analysis skills. Smartphone surveying, on the other hand, is easy to use on site and offers excellent maneuverability. It can be used indoors or in places where drones cannot fly, such as beneath slope coverings, and is well suited to routine, small-scale progress checks like “I want to check progress just a little today.” By using drones and smartphones appropriately as needed, you can build a more efficient and flexible site measurement system.