Benefits of Introducing LRTK That Revolutionizes Differential Earthwork Volume Measurement: AR Visualization & Cloud Sync to Improve On-site Efficiency

Table of Contents

• What differential earthwork volume is

• Why measuring differential earthwork volume is important (managing cut and fill, tracking construction progress)

• Traditional earthwork measurement methods and their challenges

• Advantages of calculating earthwork differences using point cloud data

• Simple point cloud surveying using smartphone RTK

• Visualizing differential earthwork with AR

• Improving on-site efficiency by instantly sharing point cloud data

• Recommendation for simple surveying with LRTK

• FAQ

What differential earthwork volume is

Differential earthwork volume (sabu n doryo) refers to the difference in soil volume between a reference terrain dataset or design model and the current terrain. For example, in site development, comparing the design’s planned ground elevation with the actual current ground shows how much more soil needs to be excavated or filled—the differential earthwork volume. By comparing pre- and post-construction terrain data, you can also calculate the actual volume of soil removed from or brought onto the site (the quantity of excavated or backfilled soil). In short, differential earthwork volume is an indicator representing the volume difference of soil between two terrain models at different times or between a design model and actual conditions. In civil engineering and construction, it is indispensable data for managing cut and fill quantities and for verifying as-built shapes after construction.

Why measuring differential earthwork volume is important (managing cut and fill, tracking construction progress)

Accurately measuring and understanding differential earthwork volume on a construction site has multiple important implications. First, it is essential for cost control and schedule management. Misjudging the difference between planned and actual excavation or fill volumes can lead to discrepancies in disposal costs for surplus soil or in the amount of fill to procure, causing extra costs or directly extending the construction period. By continuously tracking differential earthwork volume, you can appropriately adjust the number of dump trucks and heavy machines to deploy and plan soil transport, enabling efficient, waste-free construction scheduling. It also helps manage construction progress: by periodically measuring differential earthwork volume, you can quantify how much soil volume has increased or decreased since the last measurement (how much excavation or filling has progressed), allowing objective verification of whether work is proceeding as planned. If delays are detected, you can promptly take countermeasures and review the schedule.

From a quality control and as-built verification perspective, differential earthwork volume is also important. Verifying whether excavation and filling have been performed correctly to the design elevations and shapes is reliably done by checking the “difference” between the design model and the actual conditions. If deviations from the intended lines are found, corrective actions can be taken early to prevent later rework. Checking differential earthwork volume affects the overall project quality and contributes to schedule shortening and efficiency by reducing rework.

Finally, differential earthwork data greatly aids smooth communication among stakeholders. For clients, site supervisors, and heavy equipment operators to share a common understanding of soil volumes, presenting the differences visually as well as numerically is effective. For example, sharing the quantitative information “we need to remove X cubic meters of soil” makes it easier for everyone to work toward the same goal. Sharing objective differential earthwork metrics facilitates on-site communication, boosting team motivation and coordination.

Traditional earthwork measurement methods and their challenges

Traditionally, differential earthwork has mainly been measured using cross-section surveys by surveyors. Heights are measured at key site points and volumes are calculated using methods such as the average cross-section method based on those cross-sections. However, this approach has several challenges.

• Reliance on manual work and skilled craftsmanship: Setting up surveying instruments (total stations or levels), measuring visually, drafting cross-sections on paper, and calculating volumes depend heavily on the skill of experienced surveyors. Without experienced personnel it is difficult to ensure sufficient accuracy, and human errors such as misreading or calculation mistakes are common.

• Time-consuming and labor-intensive: The series of tasks from setting survey points to recording measurements, drafting drawings, and calculating quantities is very laborious and can sometimes halt overall site progress. Especially for large sites or highly undulating terrain, numerous points must be measured for accuracy, requiring long hours. Therefore, differential earthwork measurement could not be performed frequently, and missing the timing of measurements can leave site situation awareness lagging.

• Difficulty visualizing results: Survey results are reported as plan/profile drawings or numeric lists, but these do not make it easy to grasp the actual site image. Especially for clients or construction managers, it is hard to intuitively understand “where and how much soil remains” from numbers on paper, contributing to communication losses.

Thus, conventional methods suffer from uneven accuracy, low work efficiency, and difficulty in information sharing. As a new approach to solve these issues, recent attention has focused on using 3D point cloud data and AR technology, described next.

Advantages of calculating earthwork differences using point cloud data

The increasingly popular 3D point cloud data (digital surveying data composed of countless points obtained by laser scanners or photogrammetry) is bringing major innovation to earthwork calculations. Because point clouds can reproduce detailed terrain shapes, they are powerful for volume calculations. Using point cloud data, you can directly calculate volumes in 3D. Instead of estimating volumes per cross-section as before, you can compare the entire current surface with the design surface. Specifically, by overlaying the final design model (or pre-construction original ground data) with the latest current point cloud and performing differential operations, you can accurately compute cut and fill volumes down to millimeter-level precision. This eliminates human calculation errors and enables rapid, precise measurement of differential earthwork volumes.

Another major advantage of point cloud data is the visual feedback it provides. Differential results can be displayed not just as numeric tables but as color maps (heat maps). For example, if areas higher than the design (excess fill) are colored red and areas lower (insufficient excavation) are colored blue, it becomes immediately clear which areas have excess or shortage of soil. This visualization allows on-site staff to intuitively grasp the situation and instantly decide which areas to prioritize.

The efficiency and accuracy improvements from using point cloud data are already being demonstrated in real construction sites. For example, one major construction company reported that tasks which previously required four people working seven days (28 man-days) for earthwork measurement and calculation were switched to a workflow of generating point clouds from drone images and calculating volumes, completing the work with two people in one day (2 man-days). They achieved the same results with roughly 1/14 of the effort, dramatically reducing labor and time. Moreover, the as-built quantity calculation accuracy was comparable to conventional methods, with errors around 1%. In other words, point cloud–based earthwork calculation excels not only in efficiency but also in accuracy, making it increasingly important for managing differential earthwork volume.

Simple point cloud surveying using smartphone RTK

There are various methods to acquire point cloud data, such as terrestrial laser scanners and UAV (drone) photogrammetry, but a method gaining attention recently is point cloud surveying using a smartphone combined with RTK. RTK (real-time kinematic) is a technique that uses GNSS (satellite positioning) to achieve centimeter-level positioning accuracy in real time. Historically, RTK surveying required expensive dedicated GNSS equipment and base station setup, but recently small high-precision GNSS receivers that can connect to smartphones have appeared, making RTK positioning easily accessible.

By using smartphone RTK, anyone can perform high-accuracy 3D surveying easily. Simply attach a small dedicated RTK receiver (antenna) to a smartphone and launch the app; without complex setup, centimeter-level positioning begins in real time (cm-level accuracy, half-inch accuracy). Then, by waving the smartphone’s camera or LiDAR sensor and walking around the site, the surrounding terrain and structures are recorded as digital point cloud data. There is no need to carry heavy tripods to set up equipment or to apply for permissions to fly drones. It is as simple as shooting video with your smartphone—walking around the site completes a high-precision point cloud scan.

Point clouds obtained with smartphone RTK are corrected to within a few centimeters (cm-level accuracy, about half-inch accuracy). While conventional smartphone internal GPS typically has errors of several meters, RTK provides precise corrections for both horizontal position and elevation, dramatically improving the accuracy of terrain models obtained by smartphone scanning. As a result, even point clouds captured by a smartphone can be used for differential earthwork calculations with accuracy comparable to traditional laser scanner surveys. This makes it possible for on-site personnel to perform surveying themselves, preventing work stoppages while waiting for surveyors and avoiding increased outsourcing costs. In practice, some sites have reported that as-built measurements previously handled by specialized surveying teams can now be completed by a single site representative using smartphone RTK.

Visualizing differential earthwork with AR

Even if you can calculate highly accurate differential earthwork volumes using point clouds and RTK, it is important to convey the results on-site in a way that everyone can easily understand. This is where AR (augmented reality) technology proves powerful. AR overlays digital information on top of real-world images displayed on a smartphone or tablet screen. Using AR, you can overlay differential earthwork results directly onto live site footage.

Specifically, you overlay the difference results between the design model and the current point cloud (heat maps or three-dimensional excess/deficit models) on the smartphone’s camera view. For example, you can superimpose a translucent red fill model over areas that still need excavation and a translucent blue region over places that have been over-excavated below the design. Looking at the site through the phone’s screen, elevations or depressions in the soil that would otherwise be invisible appear color-coded. Differences that were hard to grasp from drawings or numbers become visually understandable on the spot.

This AR visualization dramatically smooths on-site communication. For example, if a site supervisor points the smartphone screen and says, “Let’s excavate this red area another 20 cm (7.9 in),” the heavy equipment operator can immediately understand and start work. This is far clearer and faster than unfolding paper drawings and explaining “lower the ground here by X m.” AR also allows clients or head office managers visiting the site to confirm progress and deviations from the design on the spot. By sharing as-built explanations through AR with the sensation of “seeing the real thing on site,” stakeholders gain greater confidence.

Improving on-site efficiency by instantly sharing point cloud data

Point cloud data obtained with smartphone RTK and the resulting differential earthwork calculations can be synced and shared to the cloud instantly. By uploading data to the cloud immediately after measurement, engineers in the office and team members at other locations can view the latest information. The terrain changes occurring on-site can be shared company-wide in real time, enabling rapid decision-making.

This data sharing significantly speeds up construction management. At one development site, the team performed weekly smartphone point cloud scans of the current conditions and automatically calculated weekly volume changes in the cloud. By sharing the results as heat maps during morning briefings, they could immediately determine which areas to focus excavation or filling on. Tasks that previously required a surveying team to measure multiple site locations, create CAD drawings, and calculate quantities—taking a full day or more—were completed by the site staff themselves in about 30 minutes after introducing smartphone RTK. Rapid data sharing enables each trade to respond promptly, reducing idle waiting time and ultimately shortening the construction schedule.

Accumulating data in the cloud also enables history management and centralized information. Past point clouds and differential results are saved chronologically, making it easy to verify “how much was excavated as of a given date.” Survey data that tends to be scattered across sites can be organized in the cloud so that all stakeholders access the latest version on the same platform. This helps prevent problems like construction mistakes due to outdated drawings not being shared. Cloud sync creates a system in which the entire team always shares the latest information, directly improving on-site productivity.

Recommendation for simple surveying with LRTK

As described above, leveraging advanced technologies can dramatically improve the efficiency of grasping and sharing differential earthwork volumes. However, some may feel that high-precision GNSS, point clouds, and AR sound difficult. This is where LRTK, a solution that implements these features in an all-in-one package, deserves attention. LRTK is a surveying DX platform combining a high-precision GNSS receiver, smartphone app, and cloud service, developed as an easy-to-use simple surveying tool even for non-experts.

With LRTK, you can perform centimeter-precision positioning using a small RTK receiver attached to a smartphone while scanning the site with the phone’s camera or LiDAR to generate point clouds, and then run differential earthwork calculations and visualizations in the cloud—all in one continuous workflow. In other words, the functions required for differential earthwork measurement are provided in a one-stop package. The UI is designed so site personnel can easily operate it on their own smartphones, allowing even first-time users to master it with short training.

Introducing such a tool allows companies to complete as-built surveying and earthwork calculations in-house rather than outsourcing them. This contributes to cost reduction and, through accumulated data, enables advancement of the construction PDCA cycle. Above all, as site staff themselves become proficient with digital tools, work methods change and productivity improves. Even for a single differential earthwork check, using a solution like LRTK enables a system where measurements can be “captured faster, more accurately, and shared on the spot.” This trend could be called the democratization of surveying technology. If you feel challenges in on-site efficiency or DX promotion, trying smartphone-based surveying systems like this is recommended.

FAQ

Q: What data is needed to calculate differential earthwork volume? A: Basically, you need two terrain datasets to compare. For example, “pre-construction terrain data” and “post-construction terrain data,” or a “design final model” and the “as-built data after construction.” By overlaying and calculating the difference between these two 3D datasets, you can compute fill and cut volumes. LRTK can automate this procedure with one click.

Q: What is smartphone RTK? What level of accuracy can be achieved? A: Smartphone RTK refers to connecting an external high-precision GNSS receiver (RTK antenna) to a smartphone so that RTK positioning achieves centimeter-level positioning accuracy on the phone. Because smartphone RTK can secure positioning accuracy comparable to dedicated surveying equipment, point cloud surveying with a smartphone can also maintain high accuracy. In practice, field measurements using LRTK have been confirmed in multiple locations to achieve accuracy within a few centimeters (cm-level accuracy, about half-inch accuracy).

Q: Compared to drone-based surveying, what are the advantages of smartphone point cloud surveying? A: Drone (UAV) aerial surveys can measure wide areas quickly, but they are constrained by weather and require flight permissions and other procedures. Smartphone-based point cloud surveying is done from the ground, so it can be performed even in rain and requires no prior preparation or permits, offering excellent on-site mobility. The ease of being able to measure yourself whenever needed is a major advantage. Also, because ground-level scans capture fine details, features such as slope irregularities or soil near walls that are hard for drones to capture can be recorded. Ideally, use both drones and smartphones depending on the purpose, but the convenience of completing a survey with just a smartphone is a big attraction for site personnel.

Q: Do you need special equipment for AR visualization of differences? A: No, you do not need expensive gear like special AR glasses. AR display is possible with a smartphone or tablet and a compatible app. If you want a larger screen to share on-site, use a tablet, or mirror the screen to a monitor for multiple viewers. In basic terms, you can visualize differential earthwork using your everyday smartphone or tablet.

Q: Can site staff use this? Is it okay without specialist knowledge? A: Yes, the tools are designed so site staff can use them without specialist knowledge. The smartphone surveying app (LRTK app) emphasizes intuitive operation and provides an interface that can be used without deep surveying terminology or expertise. Even first-time users can learn the operations with simple training or a manual, and the system can be introduced on-site in a short time. There are increasing examples of construction management staff without surveying expertise conducting point cloud measurements and differential checks themselves, improving operational efficiency. The era has arrived in which anyone on site can use digital surveying tools without relying on specialists.