Automate Cut-and-Fill Volume Calculations! Easy Earthwork Volume Management Using the Cloud

Table of Contents

• What are cut and fill volume calculations? Basics of soil volume change ratios

• Traditional earthwork calculation methods and their challenges

• Benefits of automating volume calculations with ICT technologies

• Easy earthwork volume management using the cloud

• Utilizing simple surveying with the latest LRTK technology

• FAQ

What are cut and fill volume calculations? Basics of soil volume change ratios

In earthwork, accurately calculating the volumes of cut and fill, that is, the amount of soil and sand, is extremely important. “Cut” refers to the work of excavating and removing soil from a hill or mound, whereas “fill” refers to the work of raising the ground using excavated soil or soil brought in from elsewhere. Calculating the volumes (the earthwork quantities) resulting from cut and fill is called “earthwork quantity calculation,” and it is an indispensable step in civil engineering works such as road construction, land development, and dam construction.

The same soil actually changes volume depending on its condition. Immediately after excavation, soil becomes airy and “loosened,” increasing in volume compared to when it was in the original ground (natural ground). Conversely, for fill, the soil spread and then compacted by rollers increases in density and reduces in volume. In other words, density changes in the order of natural ground → loosened soil → compacted soil, and earthwork volume increases or decreases accordingly. The rate of volume change due to these changes in soil condition is called the earthwork volume change ratio.

Generally, the natural ground (in its naturally compacted state) is set as 1.0, the ratio of loosened soil to natural ground is expressed as the bulking factor (L), and the ratio of compacted soil to natural ground is expressed as the compaction factor (C). For example, according to Ministry of Land, Infrastructure, Transport and Tourism standards for sandy soils, L ≒ 1.20 and C ≒ 0.90 are typical values. Simply put, soil that was 1 m^3 in the natural ground will increase to about 1.2 m^3 when excavated and decrease to about 0.9 m^3 when compacted. Therefore, when reusing cut soil for fill, the same weight and type of soil will occupy a smaller volume after compaction.

Because soil volume changes with condition, it is necessary to consider the balance between cut and fill volumes from the planning stage of construction. Ideally, planning so that the cut generated on site and the required fill are nearly equal avoids shortages or surpluses of soil, which is economical. Accurate earthwork quantity calculations allow appropriate estimates of the number of dump trucks to arrange and the amount of soil to be transported in and out, contributing to optimized schedules and costs. Also, when checking whether the as-built (final shape) volume matches the design after construction, the pre-calculated earthwork data serve as the reference. Conversely, inaccurate calculations may cause work stoppages due to insufficient soil or extra costs for surplus soil disposal.

Accurately knowing cut and fill volumes is important in situations such as the following:

• Planning and management of excavation and filling: If you calculate volumes before work, you can determine how much soil should be removed from or brought to the site, and accurately estimate the number of dump trucks and the construction schedule.

• As-built management and quality verification: At project completion, measure whether the as-built (soil volume) matches the design. If shortages or excesses are found, immediate remediation or additional imports can be decided.

• Cost calculation and settlement: Accurate earthwork quantity data form the basis for settlement and billing according to the amount of soil transported. Objective numbers are essential for shared understanding between client and contractor.

• Safety management: Properly managing temporary stockpiles and fill volumes helps evaluate collapse risks and prepare countermeasures for landslides. Knowing soil volumes is important to prevent slope instability due to overfilling.

Traditional earthwork calculation methods and their challenges

Traditionally, several methods have been used to calculate volumes on site. Typical methods and their challenges are as follows.

• Manual surveying and calculation: Site supervisors or engineers measure heights and shapes of fills and cuts using tape measures and leveling rods, assume several cross sections, and manually calculate volumes using the average section method, for example. Alternatively, they may estimate by experience from the number of dump trucks (“about ○ m^3 for ○ trucks”). These methods rely heavily on the experience and intuition of the workers, making it difficult to achieve high accuracy without skilled personnel. Calculations are time-consuming and carry the risk of human error.

• Using surveying instruments: Surveyors obtain terrain coordinate data using total stations (TS) or GPS survey instruments and later calculate volumes in the office using CAD software. Although accurate, surveying requires multiple people and long working hours, and on large development sites it is not uncommon for a team of two to three people to spend several days surveying and calculating. Data processing and drawing also take time, so the site must wait for results and real-time decisions are not possible.

• Estimates from machinery and transport volumes: When detailed surveying is difficult, the site may estimate volumes from the bucket capacity of excavators or the load capacity of dump trucks. For example, “10-ton dump trucks × ○ trucks is about ○ m^3” gives a rough estimate. However, this method remains only an approximation and cannot be considered precise.

These traditional methods share problems of being labor- and time-intensive and lacking real-time capability. Progress often had to be paused until measurement results were available, hindering efficient decision-making. Accuracy and reliability were also dependent on the skill of site personnel, which is problematic amid a shortage of skilled workers. Moreover, surveying while walking around with a tape measure on steep or unstable terrain poses safety risks.

Benefits of automating volume calculations with ICT technologies

Recently, to address these traditional challenges, new earthwork measurement methods using ICT and digital technologies have been spreading. Representative examples are 3D surveys using drones and 3D laser scanners to calculate volumes. By acquiring high-density 3D data (point clouds) and calculating soil volumes, these methods have dramatically improved both the accuracy and speed of earthwork quantity calculations.

This has made it realistic to perform volumetric measurements daily rather than only once a week, enabling site progress to be understood on the same day.

• Volume measurement using drones (photogrammetry): Small unmanned aerial vehicles equipped with cameras photograph the site from above, and software generates a 3D terrain model (point cloud) from multiple images to calculate volume. Large sites can be surveyed quickly in one operation, and soil volumes on steep slopes where people cannot enter can be measured safely. Calculating volumes from the resulting point clouds can reduce what used to take days to mere hours. In practice, there are reports where combining a drone and dedicated cloud software reduced a measurement task that previously took 4 people × 7 days to a single drone flight (tens of minutes). However, drones have operational hurdles such as aviation law restrictions, weather dependence, and the need for piloting skills.

• Measurement using 3D laser scanners: Ground-based laser scanners acquire high-precision point cloud data of the terrain with laser light. They can measure site shapes with millimeter-level accuracy (0.04 in) and calculate accurate volumes from the point clouds. However, laser scanner equipment is very expensive and requires skilled operators, making routine use by site staff difficult.

While these advanced technologies have greatly improved earthwork management, they also generated demand for “an easier-to-use method.” Although drones and large scanners are effective, many sites find them difficult to introduce due to the need for expertise, permits, and costs. In recent years, therefore, smartphone-based surveying solutions have emerged. By combining smartphones with dedicated devices and apps, anyone on site can now perform simple 3D measurements and volume calculations.

Easy earthwork volume management using the cloud

In digital earthwork calculations, cloud services play a major role. Previously, survey data had to be transferred by paper drawings or USB, but cloud integration enables immediate sharing of data between the site, the office, and stakeholders. The advantages of cloud-based volume management include:

• Real-time information sharing for quick decision-making: As soon as surveying is completed, point cloud data and calculated volumes obtained on site can be uploaded to the cloud. Even remote offices can immediately view site data over the internet, allowing those not on site to grasp the situation. For example, if the site manager shares measurement results via the cloud, head office construction managers or the client can check the numbers and 3D models on the spot and issue instructions or approvals immediately. Eliminating data transmission lag dramatically speeds up construction-related decisions.

• Accumulation and use of survey data: Storing measurement data in the cloud makes history management and visualization of progress easy. Past volume data can be retrieved later to compare and verify terrain before and after work. Overlaying planned design volumes with actual as-built volumes online and analyzing differences makes it easy to identify surpluses or shortages. Storing multiple measurement datasets in time series also enables remote monitoring of daily construction progress to confirm that earthwork is proceeding according to plan.

• Everyone on the team shares the latest data: Centralizing data in the cloud ensures all stakeholders reference the same, up-to-date information. Compared to relying on paper drawings or verbal communication, misunderstandings and transmission errors decrease and coordination between site and office becomes smoother. This enables not just “measure and finish” but an operation of “using measured data collaboratively,” significantly improving the accuracy and efficiency of site management.

Thus, cloud utilization not only makes earthwork management easier but also accelerates the PDCA cycle of the entire project and contributes to quality improvement. Integration of earthwork calculation tools with the cloud is becoming essential to realize data-driven, rational construction management.

Utilizing simple surveying with the latest LRTK technology

As a concrete example of the smartphone-based methods mentioned above, there is a solution called LRTK. LRTK is a smartphone-integrated high-precision surveying device developed with the concept of “making simple surveying possible for anyone.” By attaching a dedicated small antenna to a smartphone and using a compatible app, the smartphone instantly becomes a surveying instrument capable of centimeter-level accuracy (half-inch accuracy).

LRTK combines high-precision GNSS positioning data with 3D measurements from the smartphone’s camera or LiDAR scanner, and automatically calculates volumes from point cloud data acquired on site. Volumes of fills and excavations can be calculated on the spot, and results are displayed immediately on the smartphone screen. Measurement data are, of course, saved and synchronized to the cloud in real time, so details can be checked on office PCs and easily shared with the team.

LRTK is designed to be intuitive and usable by people without specialized knowledge after a short training. Following on-screen prompts in the smartphone app completes the survey, enabling acquisition of high-precision point cloud data even by non-experts. Because one person can operate it, the need for personnel to enter hazardous areas for manual measurement is reduced. Steep slopes can be scanned safely from a distance, reducing workload under extreme heat or on poor footing. This ease of use helps alleviate labor shortages and supports site operations that do not rely on veterans.

For example, even a mound of remaining soil several meters (several ft) high can be accurately measured by walking around with an LRTK-equipped smartphone and scanning for a few minutes. By seeing the result, the amount of soil to haul out by dump truck and deviations from the design can be immediately grasped, allowing on-site decisions to be made quickly. Tasks that previously required waiting for results or relying on experience are transformed by LRTK into data-driven, efficient construction management. Because LRTK does not require large equipment or special qualifications, earthwork measurement and management become much more accessible and faster.

The Ministry of Land, Infrastructure, Transport and Tourism is also promoting improved productivity on construction sites through ICT (“i-Construction”), and the combination of smartphone surveying devices and the cloud is likely to become a new standard in site management. Introducing these latest tools can significantly reduce the labor required for earthwork quantity calculations and accelerate on-site DX (digital transformation). Take this opportunity to adopt advanced technologies for earthwork management and realize accurate and efficient construction control.

FAQ

Q1. What are cut and fill? A. Cut is the work of removing soil by cutting into hills or mounds, and fill is the work of raising and shaping land by adding soil. For projects such as road or residential land development, it may be easy to remember that cut is excavating and removing unnecessary soil, while fill is bringing in soil to fill and raise the area.

Q2. Why does volume change between cut and fill? A. Soil becomes loosened and contains air when excavated, increasing in volume, and it becomes denser and decreases in volume when compacted. Thus, the same soil has different volumes in the natural ground, the excavated (loosened) state, and the placed-and-compacted state, so volumes differ between cut and fill.

Q3. What methods are there to calculate earthwork quantities? A. Traditionally, cross-sectional drawings were created from surveyed terrain and volumes calculated using methods such as the average cross-section method or mesh (grid) method. Recently, methods for automatically calculating volumes from drone aerial photo analysis or 3D scanner point clouds have become widespread. In any case, the common point is calculating volume based on differences in height between the reference surface and the changed terrain.

Q4. What are the benefits of managing earthwork quantities in the cloud? A. Using the cloud allows survey data and calculation results to be shared in real time among all stakeholders. You can check the latest volumes and 3D models without going to the site, enabling faster decision-making. Centralized data management also makes history comparison and analysis easy, facilitating efficient plan revision and as-built verification. In addition, accumulated cloud data can be used for future project planning and client reporting, serving as objective evidence.

Q5. How can I easily measure volumes on site? A. Even without specialized surveying equipment or advanced skills, you can now easily measure volumes using surveying devices paired with smartphones. For example, using an integrated high-precision GNSS receiver for smartphones such as “LRTK,” you can scan the terrain with a smartphone and automatically calculate fill and cut volumes on the spot. This eliminates the manual surveying and calculation work of the past and allows anyone to obtain accurate volumes in a short time. For example, measurements and calculations that used to take half a day can be completed on site in a few minutes with LRTK, and results can be shared immediately with stakeholders. No special qualifications or permits are required, making adoption easy.

Q6. What is the difference between drone-based volume measurement and smartphone surveying? A. Drone surveying has the advantage of quickly covering wide areas of terrain, but it has constraints such as flight permissions, piloting skills, and weather. Smartphone surveying with an LRTK device does not require special permits and can be performed easily on site by anyone, making it suitable for small-scale sites and routine measurements. For covering very large sites at once, drones are more efficient. It is best to use both according to site scale and conditions.

Q7. How are the volume change ratios L and C calculated? A. With the natural ground volume set to 1.0 (100%), L (the bulking factor) is calculated as loosened soil volume ÷ natural ground volume, and C (the compaction factor) is calculated as compacted soil volume ÷ natural ground volume. For example, if 100 m^3 of natural ground is excavated and L = 1.2, the loosened volume is 120 m^3. If that 120 m^3 is compacted to become fill and C = 0.9, the fill volume becomes 108 m^3. Using L and C values allows conversion of volumes between cut and fill. Note that L and C vary with soil type; national guidelines provide typical values such as L = 1.20 and C = 0.90 for sandy soils, and L = 1.25 and C = 0.90 for cohesive soils.