Table of contents

• Why on-site volume calculation is necessary

• Traditional earthwork volume calculation methods and challenges

• Volume calculation evolving with digital technology

• How to calculate earthwork volume with just a smartphone

• How high-precision surveying anyone can do works

• Benefits of using smartphone surveying

• Recommendation for simple surveying with LRTK

• FAQ

Why on-site volume calculation is necessary

On construction sites, earthwork volume management (volume calculation) associated with excavation and embankment is extremely important. For example, the amount of ground to be excavated for foundation work (excavation), the amount of fill for site formation (embankment), and the amount of surplus soil to be disposed of (excess soil) all must be accurately understood. These earthwork volumes are measured in cubic meters (m³) and are basic data directly linked to project budgets and progress management.

However, calculating volumes on actual sites is not easy. Terrain is not flat and is complex; the shapes of mounds and excavated areas are irregular. There are often discrepancies between the planned quantities and actual on-site quantities, which may require digging more soil than anticipated during planning, or cause extra costs for disposing of excess soil or bringing in additional fill. To prevent such unexpected issues, it is important to perform volume calculations on site as needed and manage earthwork quantities.

Traditional earthwork volume calculation methods and challenges

Traditionally, calculating earthwork volumes on site required time and manpower. Generally, surveyors measure ground elevations using a total station (TS) or a level and calculate volumes from terrain data before and after excavation or embankment. This method requires at least two people for surveying work (operating the surveying instrument and holding a prism or staff), and because the acquired data must be imported into a PC and processed with specialized software, it takes time to obtain results. On small sites without specialized surveying equipment, workers sometimes estimate volumes by measuring length, width, and depth with shovels and tape measures on the spot. However, such manual visual estimates and hand calculations tend to produce large errors when terrain is complex.

Furthermore, a challenge of conventional volume calculation is that it is difficult to perform frequently. Because surveying requires specialized knowledge and personnel, it is unrealistic to measure earthwork quantities every day or at every opportunity. As a result, accurate amounts of excess soil or project progress may not be known during earthwork, and there is a risk that by the time one notices, too much excavation has already occurred. In short, conventional methods take too much time and effort, making real-time on-site earthwork management difficult.

Volume calculation evolving with digital technology

In recent years, the introduction of digital technology has dramatically advanced on-site volume calculation. Methods that measure terrain by drone aerial photogrammetry or 3D laser scanning and calculate volumes with software have become widespread through initiatives like the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction. Drone photogrammetry captures the entire site from above to create point clouds and 3D models for calculating embankment and excavation volumes. High-precision laser scanners can acquire terrain point cloud data with millimeter-level accuracy. By utilizing these ICT tools, it has become more efficient than before to measure as-built shapes (post-construction shapes).

In addition to these advanced instruments, attention is also focused on the familiar device: the smartphone. Attempts to measure earthwork volumes easily using smartphone cameras and AR (augmented reality) technology are progressing, and major construction companies are developing on-site apps. For example, there are AR apps that let you place virtual survey poles (markers) on the smartphone screen and specify the area of embankment or excavation to calculate the volume on the spot. In experiments comparing smartphone measurements with high-precision laser scanners, measurement errors from smartphones were reported to be about 3–5% in some cases. Smartphone surveying has demonstrated sufficiently practical accuracy and is increasingly being recognized as a productivity-enhancing new technology, with some apps registered in the Ministry’s New Technology Information System (NETIS).

How to calculate earthwork volume with just a smartphone

So how exactly do you measure earthwork volume on site using only a smartphone? The basic flow is as follows. No specialized equipment is required—just a smartphone and a compatible surveying app. The volume calculation is completed in three simple steps:

• Select the surveying mode: Launch the app and choose a mode that matches the object to be measured (e.g., embankment volume, excavation volume, area measurement). The app guides you through the necessary steps depending on the measurement type.

• Specify the area / scan: While viewing the site through the smartphone camera, place virtual markers (poles or pins) on the target area. For example, to measure the volume of an embankment, tap to mark the four corners of the embankment base and several points at the top of the embankment on the screen. Some apps automatically scan the terrain and acquire point cloud data simply by waving the camera around while walking.

• Check the volume result on the spot: The volume of the specified area is displayed immediately on the smartphone screen. The earthwork volume (in cubic meters) is calculated, and cross-sections and height information can be viewed as needed. Results can be saved as images or recorded by overlaying measurement results on photos.

As described above, on-site volume measurement can be completed with a single smartphone. There is no need to wait for PC data processing to get measurement results; you can grasp the volume like “XX m³” on the spot, which is a major advantage. Of course, smartphone-only measurements are classified as simple surveying and accuracy can be affected by the environment. For example, AR tracking accuracy may decrease in dark surroundings or where there is little ground texture. Therefore, while not offering absolute laboratory-grade precision, smartphone surveying is very useful for routine site management and approximate as-built shape checks.

How high-precision surveying anyone can do works

Although smartphones make measurements easy, there is demand for higher accuracy for use in official measurements. This is where high-precision surveying using satellite positioning technology called RTK-GNSS comes in. RTK (Real Time Kinematic) is a technology that applies correction information to satellite positioning data such as GPS to achieve centimeter-level positioning (cm level accuracy (half-inch accuracy)) in real time. Traditionally, RTK surveying required expensive dedicated GNSS receivers and base stations, but recently products have appeared that provide this capability as compact devices that can be used with smartphones.

By using a dedicated GNSS receiver that attaches to a smartphone, the positioning error received by the smartphone can be drastically reduced. Typical smartphone internal GPS accuracy is on the order of several meters, but with an RTK-compatible device, horizontal positioning accuracy can be improved to about ±1-2 cm (±0.4-0.8 in) and vertical accuracy to about ±3 cm (±1.2 in). Because elevation can also be measured accurately, reliable vertical differences essential for earthwork volume calculation can be obtained. These RTK-GNSS devices are pocket-sized and weigh only a few hundred grams, and they can be connected wirelessly to a smartphone for ease of use. A dedicated app is installed on the smartphone, and combined with this device, anyone can easily perform high-precision positioning and surveying.

The operation on site for high-precision smartphone surveying is simple. Bring the smartphone to the point you want to measure and press a button in the app to record the latitude, longitude, and elevation of that point. The app handles all complex calculations in the background, plotting and saving measured points on a map automatically. Combined with the smartphone camera, 3D point cloud scanning of terrain is also possible. Because RTK continually keeps the device’s position accurate, walking while scanning causes little distortion in the point cloud, and all acquired points are assigned global coordinates (absolute coordinates based on a geodetic datum). In short, we have entered an era in which millimeter-level accuracy can be handled by machines even without specialized knowledge.

Benefits of using smartphone surveying

Simple surveying technology using smartphones brings many benefits to on-site earthwork management. The main advantages are summarized below:

• Labor savings / mitigation of manpower shortages: Smartphone surveying can be completed by one person. Tasks that previously required two or more people can be performed solo, enabling efficient earthwork management even on sites short of personnel.

• Immediate, real-time results: Volume results are displayed immediately after measurement, allowing on-the-spot decisions. Excess or shortage of soil can be identified instantly, enabling quick adjustments to work or arranging trucks.

• Cost reduction: It reduces the need for special surveying equipment or outsourcing to surveyors. Because smartphones and apps are relatively low-cost solutions, this can significantly reduce surveying expenses and time.

• High-frequency measurement capability: Because measurements are easy to perform, earthwork quantities can be checked frequently according to daily progress. You can measure as often as needed—even daily—so you always have numeric insight into the site’s current state and can detect deviations from the plan early.

• Improved safety: Measurements can be made without approaching hazardous areas. For example, deep excavations or high embankments can be measured remotely with the smartphone camera, reducing the risk of workers entering unsafe zones. Because surveying takes little time, interruptions to site work are minimized, contributing to overall safety management.

• Data accumulation and sharing: Earthwork information can be recorded as digital data, making it easy to review later or share with other stakeholders. With cloud-integrated systems, data measured on site can be viewed immediately in the office. If saved together with photos and drawings, visualizing earthwork volumes makes it easier for all stakeholders to understand the situation.

In this way, smartphone surveying enhances on-site productivity and safety and facilitates smoother communication. It is a powerful tool for promoting DX (digital transformation) in civil engineering works.

Recommendation for simple surveying with LRTK

One solution that maximizes the convenience and accuracy of smartphone surveying described above is LRTK. LRTK is a modern simple surveying system that uses a small RTK-GNSS receiver attached to a smartphone to dramatically streamline on-site earthwork management. Simply attaching this device to a smartphone enables centimeter-level positioning (cm level accuracy (half-inch accuracy)) that used to require large equipment, turning the smartphone itself into a high-precision surveying instrument. Weighing about 125 g and compact, it is easy to carry and contains a built-in battery so it does not get in the way on site. It can be attached to a dedicated smartphone cover with one touch, allowing quick deployment and immediate surveying when needed.

With the LRTK app, everything from coordinate measurement to volume calculation and 3D surveying via point cloud scanning can be completed with a single smartphone. Acquired data can be uploaded directly to the cloud so that office staff can check on-site conditions remotely. For example, scanning terrain with LRTK to obtain as-built point cloud data and overlaying it with the design 3D model in the cloud makes it possible to instantly calculate volume differences between design and as-built. Tasks that previously required specialized technicians, such as advanced surveying and as-built management, can be performed accurately and quickly by anyone with LRTK.

LRTK is also designed to be affordable, and we are approaching an era in which each site worker can have a unit. As an “one-device-per-person万能 surveying instrument,” you can take it from your pocket when needed, measure, and immediately understand earthwork volumes—such a daily routine is becoming reality. Smartphone surveying with LRTK is a reliable ally that dramatically improves on-site efficiency including earthwork management. If you are interested, try this new surveying experience once to feel its convenience and accuracy.

FAQ

Q: How accurate are volumes measured with a smartphone? A: When using only a smartphone AR surveying app, errors are generally on the order of a few percent depending on conditions. Some reports comparing smartphone results with high-precision laser scanners showed differences of about 3–5%. While this falls within the scope of simple surveying, it is accurate enough for routine construction management. If stricter accuracy is required, combining the app with an RTK-compatible device can achieve centimeter-level accuracy.

Q: What equipment or smartphone is needed to measure earthwork volume? A: Basically, many apps will run on recently released, high-performance smartphones. Devices with strong AR capabilities, such as iPhones or iPads, will measure especially smoothly, and models equipped with LiDAR sensors can be expected to provide more stable measurements. For higher accuracy, prepare an RTK-GNSS receiver (for example, a smartphone-mountable device like LRTK). Attaching it to the smartphone enables use of high-precision positioning data not obtainable with a smartphone alone.

Q: Can it be used without specialized knowledge or surveying qualifications? A: Yes. Smartphone surveying apps and systems like LRTK are designed to be usable even by beginners. You simply follow on-screen instructions, so no special surveying skills are required. Tasks that used to be handed to surveyors can be performed easily on site by anyone. However, documents submitted to government agencies and other formal surveying work may require qualified personnel, so it is best to view smartphone surveying as suited to on-site internal work and routine management.

Q: How does smartphone surveying compare with drone surveying? A: Drone surveying has the advantage of capturing wide areas at once and is suitable for large-scale site formation or forest terrain surveys. On the other hand, it requires flight permissions and piloting skills, and is more susceptible to weather. Smartphone surveying’s biggest feature is ease of use; it is useful on small to medium sites and in environments where drones cannot fly, such as indoors or in tunnels. It also requires no lengthy preparation and can be performed immediately when needed. Using drones and smartphones selectively or in combination to complement each other can measure sites more efficiently.

Q: Can data measured by a smartphone be used as official as-built quantities? A: At present, smartphone simple surveying data is mainly used for construction management and internal verification. For official as-built records in public works, surveys meeting prescribed standards (for example, final surveys or surveys with supervising staff present) may be required. However, data obtained by smartphone surveying serves as objective evidence and can be useful for sharing site status among stakeholders or as a reference for later precision surveying. As the technology’s reliability increases, it may be recognized as an official measurement method in the future.

Q: What scale or area can be measured at once? A: With smartphone-only AR surveying, depending on the app, you can typically measure an area of about several hundred to several thousand square meters at once. For example, some apps have been used to measure an embankment of about 1000 m² (equivalent to 30 m × 30 m (98.4 ft × 98.4 ft)) at one time. For larger sites, you can divide the area and measure each section and then combine the data. High-precision smartphone surveying such as LRTK has successfully scanned large earthworks exceeding 200 m³. For even larger terrain, it is realistic to combine drone aerial surveying or terrestrial laser scanning to cover the area. Choose and combine surveying methods according to the site scale.