Table of Contents

• Why embankment volume calculation is important

• Traditional methods for calculating embankment volume

• Problems arising from traditional methods

• Basic knowledge of as-built management and earthwork quantity management

• New norms brought by ICT and 3D surveying

• What is simple surveying with LRTK?

• FAQ (Frequently Asked Questions)

Why embankment volume calculation is important

In civil engineering and construction, embankment (morido) refers to raising the ground to a specified height by placing soil or fill, and accurately calculating and grasping its volume is extremely important. Misjudging the amount of fill or excavation can significantly affect construction planning, costs, and quality. Here we organize the main situations where embankment volume calculation is required and why it matters.

• Construction planning and logistics management: By accurately calculating how much soil needs to be transported in, out, or disposed of, you can properly plan the number of dump trucks, transport trips, and the construction schedule. If fill and excavation quantities are known in advance, rework or delays caused by excess or shortage of soil can be avoided.

• As-built management and quality assurance: As-built management involves checking at project completion whether the embankment has the design height, shape, and volume. If the fill is insufficient, the required bearing capacity or stability may not be achieved; conversely, too much fill can exceed the design height. Using objective volume data to correct shortages or excesses ensures quality.

• Progress quantity management and cost calculation: In earthworks, billing and payments are made based on the amount of soil delivered or placed. Calculating an accurate embankment volume that both the client (owner) and contractor can agree on is essential to prevent contractual disputes and to properly manage costs.

• Safety management: The amount of fill or temporarily stockpiled soil directly affects safety. Excessive fill increases overload and the risk of collapse, while overly deep excavations may cause surrounding slopes to fail. Maintaining appropriate soil quantities is important from the perspective of slope stability calculations and landslide prevention.

As described above, calculating embankment volume is indispensable at every stage of construction—planning, execution, inspection, and settlement. Whether timely and accurate earth quantity data can be obtained greatly influences site efficiency and decision-making speed.

Traditional methods for calculating embankment volume

Various methods have traditionally been used to determine embankment volume. Below are representative conventional methods and their overviews.

• Rough estimate by average cross-sectional area method: The most basic method is to cut cross-sections of the embankment at regular intervals, measure the area of each cross-section, take the average, and multiply by the distance between sections to obtain volume (average cross-sectional area method). For example, if the cross-sectional area at the start of a segment is A1, at the end is A2, and the segment length is L, the volume V can be roughly calculated as `V = ((A1 + A2) / 2) × L`. In the field, heights have traditionally been measured with a staff (leveling rod) or level, and cross-sectional areas calculated on paper drawings with manual arithmetic. This method has long been used for estimating embankment volumes for railways and roads, but improving accuracy requires dividing sections into finer intervals.

• Calculation using surveying instruments and drawings/CAD: Surveyors use total stations (electronic distance measurement) or GPS survey equipment to measure ground elevations before and after embankment work on a fine mesh, and calculate volume from the coordinate data. Traditionally, existing ground and design ground longitudinal and cross-sectional drawings are produced and volume is calculated from the difference in cross-sectional areas. Later, survey data have been imported into civil engineering CAD software on PCs to create 3D models of the embankment and original ground and automatically compute volumes. Accuracy improves, but this method requires specialist knowledge and time for surveying and data processing.

• Estimation from equipment or hauled soil quantities: As a simple estimate, sites sometimes back-calculate embankment volume from equipment or truck usage. For example, using the experience-based estimate that “we transported X loads with 10-ton dump trucks, so approximately Y cubic meters,” or estimating soil volume from the bucket capacity and number of cycles of an excavator. However, these are rough indicators and tend to deviate from actual volumes, so they are not suitable for formal verification.

Thus, traditional embankment volume calculation combined manual field measurement, drawing- or software-based calculation, and experience-based estimation. Each method can produce usable results, but there has been room for improvement in accuracy and efficiency, and the issues described below have been pointed out.

Problems arising from traditional methods

The conventional methods described above have raised the following concerns and complaints from sites.

• High labor and time burden: Measurements with tapes and staffs and preparing cross-section drawings require many workers and long hours. Administrative tasks to compile survey results into drawings and tables also impose a large burden on site engineers. With severe labor shortages, always arranging specialized surveyors raises costs and makes it difficult to proceed efficiently within schedule.

• Limited measurement points and accuracy concerns: The number of points that can be measured by hand is limited, so it is difficult to fully grasp the entire embankment. Relying on a limited set of measurement points risks missing areas where fill is insufficient or excessive. Especially for large embankments, manual measurement may lead to last-minute corrections when inspections find localized deviations from drawings.

• Dependence on individuals and human error: Estimates based on experience and intuition vary with the skill of the person in charge and lack objectivity. On busy sites, human errors such as recording mistakes or forgetting to take photos are common. For example, if measurements or photos are not taken before backfilling an underground object, no evidence remains after completion and disputes may arise. Variability in who measures and the possibility of mistakes pose reliability issues.

• Lack of real-time results and safety concerns: Traditional methods require taking measured data back to the office for calculation and drafting, so results are not available immediately on site. This delay can lead to corrective work falling behind. Measuring on irregular terrain or unstable fill that has not been fully compacted is dangerous. Working on steep slopes with poor footing to support a staff carries fall risks, and such safety concerns are a practical issue on sites.

Because of these problems, sites have long sought a “more efficient and reliable method for managing embankment volume.” The next section explains recent solutions using ICT and 3D measurement technologies.

Basic knowledge of as-built management and earthwork quantity management

Here we briefly organize the terms as-built management (dekigata) and earthwork quantity management, which are important when discussing quality and quantity control on construction sites.

• As-built management: As-built (dekigata) refers to the final shape of the structures or formed terrain produced by construction. As-built management is the process of confirming and recording—based on measurement data—whether the completed parts match the design in shape and dimensions. Especially in public works, measurements are taken at prescribed points according to as-built management standards set by the client (administration) to check deviations from design values. These results are used to determine inspection acceptance and handover, making as-built management a key element of construction quality assurance.

• Earthwork quantity management: Earthwork quantity management is, as the name suggests, the management of the amount (volume) of soil handled in the work. In embankment and excavation works, it is necessary to grasp and record the actual soil volumes moved in or out or placed compared with estimated quantities at the planning stage. Regular measurement during the work to identify deviations from the plan is required. Earthwork quantity management is often carried out together with as-built (shape) verification, and it is common to measure as-built quantities (embankment and excavation volumes) simultaneously with as-built management. This enables evaluation and control of project outcomes from both quality and quantity perspectives.

In short, as-built management checks “shape (quality),” while earthwork quantity management checks “quantity (amount).” Traditionally, as-built management confirmed shape and then quantities were calculated separately, but recently 3D technologies (described later) are making it common to integrate shape measurement and volume calculation into a single process.

New norms brought by ICT and 3D surveying

Against the backdrop of the issues described above, digital technologies for embankment volume management have increasingly penetrated sites in recent years. The key is the introduction of ICT construction and 3D surveying technologies. Supported by the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* policy, high-density non-contact measurement using drones and laser scanners has become practical. This has brought what can be called a “new norm” in as-built and earthwork quantity management.

Benefits of point cloud data measurement in 3D

A point cloud is a collection of countless measurement points (XYZ coordinates) that records the site’s shape. Photogrammetry from drones or terrestrial 3D laser scanners can scan wide areas of terrain and structures in a short time to obtain high-precision 3D models. Using point cloud data offers the following benefits.

• Can cover the entire site: Unlike manual measurement, point clouds can densely capture every part of the terrain. Surface irregularities and subtle unevenness are recorded without omission, enabling detailed detection of differences from design. This reduces oversights and allows early detection and correction of significant quality issues. The Ministry of Land, Infrastructure, Transport and Tourism has newly established an as-built inspection method called “surface management,” which evaluates the entire finished surface using point clouds and promotes more comprehensive inspection than conventional point-by-point checks.

• Immediate volume calculation: By comparing the measured current point cloud with the design data, the volume difference for embankment or excavation can be calculated automatically. Previously, manual cross-section calculations or CAD sectional analyses were required, but with point cloud measurement, volumetric calculations can be completed instantly in software. For example, measurements and calculations that used to take two to three people several days for a large development have been completed in less than half a day using drone aerial photography and specialized software in some cases. Being able to grasp earth volumes immediately on site enables instant decisions on construction progress and the necessity of additional fill.

• Streamlined inspection and documentation: Acquired point cloud data can be stored and used as digital 3D records. Some analysis software can automatically display deviations from design as color maps or generate pass/fail reports. This allows partial automation of as-built inspections and quantity reporting, greatly reducing tasks such as hand-drawing drawings or copying numbers into spreadsheets. A survey by the Ministry showed that earthworks using ICT construction (3D surveying, machine guidance, etc.) achieved an average reduction in total work hours of about 30%, demonstrating efficiency improvements through digitalization.

With the introduction of 3D surveying technologies, the accuracy and speed of embankment volume management have dramatically increased. The era in which “measuring embankment volume in 3D is the norm” is coming. In fact, public works inspection standards are being revised accordingly, and 3D as-built management (surface management) is becoming the new standard for earthworks and paving. As-built and quantity management, which used to rely on veteran intuition and manual work, are evolving into a new norm where anyone can perform them accurately and quickly through data utilization.

What is simple surveying with LRTK?

As 3D surveying becomes the new norm, demand has also grown for “measurement tools that anyone can use more easily.” Drones and high-performance laser scanners are effective but pose hurdles such as specialist knowledge, aviation law restrictions, and high equipment costs, making them difficult to adopt on small- to mid-sized sites. One solution that has emerged is a new surveying device that combines a smartphone with RTK technology. A representative example is LRTK, developed by the Tokyo Institute of Technology spin-off startup Lefixea.

LRTK (Lefixea RTK) is a high-precision surveying system consisting of a pocket-sized RTK-GNSS receiver that attaches to a smartphone or tablet and a dedicated app. The real-time kinematic (RTK) method corrects satellite positioning errors for GPS and other systems, achieving centimeter-level positioning accuracy (cm level accuracy (half-inch accuracy)) with a smartphone. In addition, by using the smartphone’s built-in camera and LiDAR sensor (on supported models), surrounding terrain and structures can be 3D scanned, and high-precision positional coordinates are appended to the acquired point cloud so it can be treated as an accurate 3D model. It can link with cloud-based analysis functions on the spot and automatically calculate and display embankment or accumulated soil volumes with a single tap. Processes that were previously performed separately—from surveying to calculation—are integrated on the smartphone with LRTK, making it revolutionary that anyone can easily calculate embankment volumes on site.

With LRTK’s arrival, as-built surveying and volume calculation that previously required expensive specialized equipment and highly skilled personnel have become much more accessible. The compact device simply attaches to a smartphone, offering excellent mobility and allowing workers to walk and quickly measure even in confined sites or on sloped terrain with elevation differences. In just a few minutes of scanning, wide-area point cloud data can be acquired and embankment volume can be confirmed immediately, dramatically speeding up on-site decision-making. In terms of accuracy, LRTK achieves positional precision that previously required surveying equipment costing several million yen, ensuring reliability comparable to conventional methods.

There are also major advantages in ease of adoption. Because LRTK leverages smartphones, it can be operated if you already have an existing smartphone or tablet, thus reducing initial costs, and its operation can be learned with short training even by non-surveyors. No special flight permits or licenses are required, making it easy to incorporate into daily construction management, and its use is spreading as a “one-per-person” site tool. In advanced construction sites, supervisors and workers themselves increasingly use LRTK to check as-built conditions and earthwork quantities, and its convenience and usefulness are highly valued.

Thus, simple surveying with LRTK can be said to embody the new norm of embankment volume management at the site level. It supports the 3D surveying required by the Ministry’s ICT/*i-Construction* initiatives, and the acquired point cloud data meet the accuracy requirements and delivery formats of as-built management guidelines. LRTK, which realizes substantial labor and time savings compared to conventional methods while improving the reliability of quality and quantity management, will be a powerful tool for future site operations. Consider adopting this new norm at your site and stepping into the next stage of embankment volume management.

FAQ (Frequently Asked Questions)

Q: How is embankment volume calculated? A: Traditionally, embankment volume has been estimated by measuring cross-sectional areas and using the average cross-sectional area method or calculated from survey data using drawings or CAD software. First, measure the shapes of the original ground and the finished embankment surface, and determine the volume from their difference. The detailed procedure is to extract cross-sections at regular intervals, calculate each section’s area, compute the partial volume for each segment as average cross-sectional area × length, and sum them for the total. Recently, the mainstream method is shifting to using 3D models such as point clouds to automatically calculate the difference volume between the embankment and the design surface in software.

Q: What is the difference between embankment and excavation? A: “Embankment” means raising low ground by placing soil or fill, while “excavation” means lowering high ground by digging. In road construction and land development, embankment and excavation are performed as needed to achieve design heights and gradients. Embankment and excavation volumes are complementary concepts, and construction planning considers the balance between them (the so-called “earthwork balance”). If soil excavated from cut sections can be reused as fill, it is economical; if insufficient, soil is brought in from outside, and if surplus occurs it is transported to disposal sites.

Q: What is as-built management? A: As-built management is the construction management process of confirming and recording whether the final shape and dimensions of completed structures or terrain match the design documents. For example, road base thickness and embankment height are measured at completion and compared with design values to check conformity. In public works, measurements at prescribed points based on as-built management procedures are mandatory, and the results are organized into tables and photo records for submission. Passing as-built management inspection is an important requirement for recognizing project completion and is a practice to guarantee construction quality.

Q: What technologies can be used for earthwork quantity management? A: Advanced earthwork quantity management methods using ICT technologies have increased recently. Representative methods include point cloud surveying by drone aerial photography and 3D laser scanners. These methods can digitize wide-area terrain into 3D data in a short time and accurately calculate embankment and excavation volumes by comparing with design models. Also attracting attention are smartphone-integrated simple surveying devices (such as LRTK). These devices obtain high-precision point clouds using a smartphone and GNSS and automate volume calculation in the cloud, enabling immediate on-site grasp of earth quantities. The new trend is to perform objective earthwork quantity management with digital measuring instruments rather than manual work or intuition.

Q: What is LRTK? A: LRTK is a surveying system consisting of a small RTK-GNSS receiver that attaches to a smartphone and a dedicated app. The real-time kinematic (RTK) technique corrects satellite positioning errors to achieve centimeter-level positioning with a smartphone. In addition, the smartphone’s camera and LiDAR can scan the site to obtain point cloud data, and volumes such as embankment can be calculated immediately from the acquired data. Compared with conventional surveying equipment, LRTK offers superior portability and cost-effectiveness, and is designed to be easy to use even for non-specialists, enabling simple as-built and quantity measurements by anyone.

Q: I hear terms like i-Construction and ICT construction—what do they mean? A: i-Construction is the name of the Ministry of Land, Infrastructure, Transport and Tourism’s initiative to revolutionize productivity on construction sites. It aims to streamline and enhance surveying, design, construction, and inspection processes by utilizing ICT (information and communication technology). Specifically, it involves using 3D survey data, drones, machine guidance (automated control of construction machinery), and BIM/CIM (design and construction based on 3D models) to digitize construction management that was once heavily manual. ICT construction refers broadly to construction work using such ICT technologies, and in embankment volume management, 3D point cloud-based as-built management (surface management) is becoming the new standard. Digitalization in the i-Construction era dramatically improves quality, safety, and efficiency in construction management.