AR-Visible Differential Earthwork Volumes! Improve Site Efficiency by Instantly Sharing Smartphone RTK Point Cloud Measurement Data

Table of Contents

• What is differential earthwork volume?

• Why understanding differential earthwork volume is important

• Conventional earthwork measurement methods and their challenges

• Advantages of calculating earthwork differences with point cloud data

• Simple point cloud surveying using smartphone RTK

• Visualizing differential earthwork volume with AR

• Improving site efficiency by instantly sharing point cloud data

• Recommendations for simple surveying with LRTK

• FAQ

What is differential earthwork volume?

Differential earthwork volume refers to the difference in soil volume between a reference terrain dataset or design model and the current terrain. For example, in earthworks, comparing the design planned ground elevation with the current ground shows how much soil still needs to be excavated (or filled); that amount is the differential earthwork volume. Comparing terrain data from before and after construction can also calculate the actual volume of soil removed or brought in (the amount of excavated material or backfill). In short, differential earthwork volume is an indicator representing the volume difference of soil between two points in time or between different models, and on civil engineering and construction sites it is indispensable data for managing cut-and-fill quantities and as-built verification.

Why understanding differential earthwork volume is important

Accurately understanding differential earthwork volume on a construction site has several important implications. First, it is indispensable for cost and schedule management. Misjudging the difference between planned excavation/fill quantities and the actual amounts can throw off disposal costs and the amount of backfill to procure, directly leading to extra costs or schedule delays. By continuously tracking differential earthwork volume, you can properly adjust the number of dump trucks to arrange and the plan for soil transport, enabling efficient construction planning.

From the perspective of quality control and as-built verification, differential earthwork volume is also important. To verify whether excavation and filling have been performed to the design elevations, comparing the design model with the current condition and checking the differences is the most reliable method. If there are excesses or shortages relative to the specified lines, corrective actions can be taken early. Confirming differential earthwork volume influences the overall project quality and efficiency by preventing rework and redoing operations.

Furthermore, differential earthwork volume data aids smooth communication among stakeholders. For owners, site supervisors, and heavy equipment operators, sharing not only numbers but also visual representations of differences helps create a common understanding of soil volumes. Sharing quantitative information such as “we need to move X cubic meters of soil” makes it easier for everyone on site to work toward the same goal.

Conventional earthwork measurement methods and their challenges

Traditionally, on-site earthwork measurement has mainly relied on cross-section surveying by surveyors. Elevations are measured at key points of the work area, cross-sectional drawings are created, and excavation/fill volumes are calculated from those sections. However, this method has several challenges.

• Work reliant on manual labor and craftsmanship: Setting up surveying instruments (total stations or levels), taking measurements, producing cross-sections on paper, and calculating volumes depend on the skills of experienced surveyors. Ensuring accuracy is difficult without experienced personnel, and human errors such as misreading or calculation mistakes are common.

• Time-consuming and labor-intensive: Tasks such as placing survey points, recording measurement points, drafting, and quantity calculation are laborious, and may halt overall site progress. On large sites or highly undulating terrain, obtaining sufficient points for accuracy can take a long time. Therefore, differential earthwork volume measurements could not be performed frequently, and missing the right timing often meant site situational awareness lagged behind.

• Difficult to visualize results: Survey results are reported as cross-sections or numerical tables, which are not easy to link to the site image. Especially for owners and construction managers, it is hard to intuitively grasp where and how much soil remains from numbers on paper, contributing to communication loss.

As described above, conventional methods present scattered challenges such as variation in accuracy, inefficient work, and difficulty in information sharing. Point cloud data and AR technologies, discussed next, are attracting attention as new approaches to solve these issues.

Advantages of calculating earthwork differences with point cloud data

Rapidly spreading in recent years, 3D point cloud data is revolutionizing earthwork volume calculations. Point cloud data is digital data that represents the surface of terrain or structures as a multitude of points (a set of 3D coordinates). Because detailed landforms can be reconstructed from this point cloud, it is powerful for volume calculations.

Using point cloud data, you can directly calculate volumes from 3D models. Instead of estimating volumes per cross-section as in conventional methods, you can compare the entire current terrain with the design surface. Specifically, overlay the completed design model (or the pre-construction original terrain data) with the latest on-site point cloud and compute the differences. With software, pressing a button to compute the difference between the two terrain models yields cut and fill volumes with millimeter-level accuracy. This eliminates human calculation errors and allows precise differential earthwork volumes to be determined quickly.

Another advantage of point cloud data is the visual feedback it provides. Difference results can be displayed not only as numbers but also as color maps (heat maps). For example, coloring areas higher than the design in red and lower areas in blue makes it immediately obvious where there is excessive fill or unexcavated soil. Visualizing differences with point cloud data enables site personnel to intuitively grasp the situation and instantly determine priority work areas.

Simple point cloud surveying using smartphone RTK

There are various methods to acquire point cloud data, such as laser scanning (LiDAR) and drone photogrammetry, but a recently notable approach is point cloud surveying combining a smartphone with RTK. RTK (Real-Time Kinematic) is a technology that uses GNSS (Global Navigation Satellite Systems) to achieve centimeter-level positioning accuracy in real time. Until now, RTK surveying required expensive dedicated GNSS equipment and base station setup. However, recent technological advances have produced compact high-precision GNSS receivers that can connect to smartphones, making RTK positioning easily accessible.

With smartphone RTK, anyone can perform high-precision 3D surveying easily. By attaching a dedicated device to a smartphone and launching an app, high-precision positioning begins in real time without complex setup. Point cloud data is acquired by walking around the site while pointing the smartphone camera or LiDAR sensor, and the surrounding terrain and structures are captured as sequential digital point clouds. There is no need to carry heavy tripods to set up machinery or apply for drone flight permission. Just moving the smartphone around the site as if recording a video enables a high-precision point cloud scan to be completed with ease.

Point cloud data obtained with smartphone RTK is corrected to positioning errors within a few centimeters. While standalone smartphone GPS previously had meter-level errors, RTK corrects both horizontal and vertical positions precisely, dramatically improving the accuracy of terrain models obtained by point cloud measurement. Consequently, point cloud data captured by smartphones can be used for differential earthwork volume calculations with accuracy comparable to conventional laser scanner surveys. This enables site personnel themselves to perform surveying, preventing work stoppages waiting for survey teams or increased outsourcing costs. For example, measurement tasks that previously required specialized surveying teams or external contractors can be completed by a single site person using smartphone RTK.

Visualizing differential earthwork volume with AR

Even if high-precision differential earthwork volumes are calculated using point cloud data and RTK, it is important to communicate the results to the site clearly. This is where AR (Augmented Reality) technology is highly effective. AR overlays digital information onto real-world images shown on a smartphone or tablet screen. Using AR, you can directly overlay and display differential earthwork results on the actual site view.

Specifically, the difference results between the design model and the current point cloud (heat maps or 3D models) are displayed on the smartphone camera feed. For example, semi-transparent red fill models can be overlaid on areas that still require excavation, while blue zones can indicate places that have been over-excavated and are now too low. When viewing the site through a smartphone screen, invisible mounds and depressions appear colored and floating over the real scene. This makes differences that were hard to intuit from drawings or numbers visually understandable on the spot.

AR visualization dramatically smooths on-site communication. For example, if a site supervisor points a smartphone and says, “Let’s dig this red area down another 20 cm,” an equipment operator can immediately grasp the situation from the visual cue. This enables instructions that are understood at a glance, rather than spreading paper drawings and saying “lower that ground by X m.” Additionally, when owners or construction managers visit the site, AR allows them to confirm current progress and differences from the design right there. As-built explanations that used to be presented in reports or drawings can now be shared as a real-world visual experience through AR, leading to more reliable explanations.

Improving site efficiency by instantly sharing point cloud data

Point cloud data obtained with smartphone RTK and the resulting differential earthwork calculations can be shared instantly via the cloud. Uploading data to the cloud immediately after measurement allows engineers in the office and other team members to view the latest information. This enables the entire organization to share site changes in real time and use them for rapid decision-making.

The effects of data sharing are particularly evident in faster construction management. In one development site, they performed a smartphone point cloud scan of current conditions once a week and automatically calculated weekly earthwork changes in the cloud. By sharing those results as heat maps during morning briefings, they could instantly determine “which areas should be prioritized for excavation or filling.” Whereas conventional workflows required a surveying team to measure cross-sections, produce CAD drawings, and compute quantities—taking more than a day—after introducing smartphone RTK the site representative can complete the process in about 30 minutes. Rapid data sharing enables each trade to act quickly, reducing idle time and contributing to shorter schedules.

Accumulating data in the cloud also enables history tracking and centralized information management. With past point cloud data and difference results stored in time series, it is easy to look back and verify “how much was excavated at that time.” Survey data, which tends to be scattered across different sites, is organized in the cloud so all stakeholders can access the latest version on the same platform. This prevents issues such as missed information or using the wrong drawings.

Recommendations for simple surveying with LRTK

By leveraging the advanced technologies described above, the process of understanding and sharing differential earthwork volume can be drastically streamlined. However, some may feel intimidated by terms like high-precision GNSS, point clouds, and AR. One solution to consider is LRTK, an all-in-one solution that brings these capabilities together. LRTK is a surveying DX platform that combines a high-precision GNSS receiver, a smartphone app, and cloud services, developed as an easy-to-use simple surveying tool even for non-experts.

With LRTK, you can perform centimeter-level positioning with a compact RTK receiver attached to your smartphone while scanning the site with the phone’s camera or LiDAR to create point clouds, and then calculate and visualize differential earthwork volumes in the cloud—executing the entire workflow end-to-end. In other words, it is a one-stop package of functions needed for differential earthwork measurement. The UI is designed for ease of use on a worker’s own smartphone, so even first-time users can master operations with short training.

Introducing such a tool allows companies to bring as-built surveying and earthwork calculations in-house instead of outsourcing them. This contributes to cost savings, and by leveraging accumulated data, it is possible to advance the construction PDCA cycle. Above all, when site workers themselves master digital tools, their way of working changes and productivity improves. Even for a simple task like confirming differential earthwork volume, using a solution like LRTK enables a system where you can “find out quickly and accurately” and “share it on the spot.” A movement that could be called the democratization of surveying technology is already underway. If you feel challenges in improving site efficiency or promoting DX, consider trying smartphone-based surveying systems like these.

FAQ

Q: What data is needed to calculate differential earthwork volume? A: Basically, you need two terrain datasets to compare (or a terrain dataset and a design model). For example, point cloud data of the “pre-construction terrain” and the “post-construction terrain,” or a combination of the “design finished model” and the “current point cloud.” Overlaying these datasets allows you to compute the differential earthwork volume.

Q: What is smartphone RTK? Is the accuracy sufficient? A: Smartphone RTK refers to connecting a high-precision GNSS receiver to a smartphone and using RTK technology to achieve centimeter-level positioning on the phone. It can provide positioning accuracy equivalent to dedicated equipment, so point cloud surveying with a smartphone can achieve high accuracy. In practice, many sites have confirmed measurements within errors of a few centimeters.

Q: Compared to drone surveying, what are the advantages of smartphone point cloud surveying? A: Drone photogrammetry can quickly survey wide areas, but it is more susceptible to weather and flight restrictions. Smartphone point cloud surveying can be performed on the ground even in rain, requires no setup or permissions, and therefore excels in mobility. Because it scans from ground level, it can capture details such as wall irregularities that drones may miss. Both methods have their uses depending on the task, but the convenience of completing a survey with a handheld smartphone is a major advantage for site personnel.

Q: Do I need special equipment for AR visualization of differences? A: No. In most cases, commercially available smartphones or tablets are sufficient. Since AR display is done through the smartphone screen, a compatible app is all you need; special AR glasses are not required. If you want to share on a larger screen, use a tablet for a bigger view or mirror the display to a large monitor when everyone on site needs to see it.

Q: Can site staff use this? Is specialized knowledge required? A: Yes. These systems are designed so site staff can use them without specialized knowledge. Smartphone surveying apps have intuitive UIs so users can operate them without being familiar with complex technical terms. Even beginners can learn quickly with simple training or manuals. In fact, there are increasing examples where construction management staff without surveying expertise perform point cloud surveys and differential checks themselves and achieve efficiency gains.

Q: How much does implementation cost? A: Compared to acquiring large surveying equipment and dedicated software, solutions using smartphone RTK are significantly lower cost. You can leverage existing smartphones, and the additional required equipment is typically just a small GNSS receiver, keeping initial investment down. Considering that surveying previously outsourced can be done in-house, the overall cost-effectiveness is high.

Q: Point cloud data can be large—can smartphones and the cloud handle it? A: High-density point cloud files can indeed become large. However, smartphone point cloud surveying solutions automatically compress and optimize data or scan only necessary areas to keep sizes manageable. By combining with cloud services, heavy processing is done server-side, and only necessary information is transferred to the smartphone. This design prevents overloading the phone’s storage or processing capacity. With adequate network connectivity, heavy 3D data can be handled smoothly via the cloud. Therefore, you can confidently work with large-scale 3D data.