Table of Contents

• What are cut and fill volume calculations? Basics of earthwork swell and shrinkage rates

• Traditional earthwork calculation methods and their challenges

• Benefits of automating volume calculations with ICT technologies

• Easy earthwork management using the cloud

• Utilizing simple surveying with the latest LRTK technology

• FAQ

What are cut and fill volume calculations? Basics of earthwork swell and shrinkage rates

In earthwork, accurately calculating the volumes of cut and fill, that is, the amount of earth and soil, is extremely important. A cut is the operation of excavating a hill or slope to remove soil, while a fill is the operation of raising the ground by placing excavated soil or imported fill. Calculating the volumes (the “earthwork quantity”) resulting from cuts and fills is called “earthwork volume calculation,” and it is an indispensable process in civil engineering works such as road construction, land development, and dam construction.

The same soil actually changes volume depending on its state in cut and fill operations. Immediately after excavation, soil becomes loosened and contains air, becoming a fluffy, “loosened state,” so its volume increases compared with when it was in the original ground (in situ). Conversely, for fills, the placed soil is rolled and compacted with rollers to “densify” it, which increases density and reduces volume. In other words, density changes in the order of in situ ground → loosened soil → compacted soil, and the earthwork quantity increases or decreases accordingly. The rate of volume change due to these state changes is called the earthwork swell/shrinkage rate.

Generally, the in situ ground (natural compact state) earthwork rate is set to 1.0, the factor by which loosened soil volume becomes a multiple of the in situ volume is called the swell factor (L), and the factor by which compacted soil volume becomes a multiple of the in situ volume is called 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. Simply put, 1 m³ (35.3 ft³) of soil in situ becomes about 1.2 m³ (42.4 ft³) when excavated and about 0.9 m³ (31.8 ft³) when compacted. Therefore, when reusing soil from cuts for fills, the volume in the fill will be smaller even if the weight and type of soil are the same.

Because earthwork quantity changes with soil state, it is necessary to consider the balance between cut and fill volumes from the planning stage. Ideally, plan so that the cut volume generated on site and the required fill volume are nearly equal to avoid material shortages or surpluses, which is economical. Accurate earthwork calculations allow appropriate estimation of the number of dump trucks to arrange and the amount of soil to be moved in or out, leading to optimization of schedule and cost. Also, when checking whether the as-built (completed) shape matches the design volume after construction, the pre-calculated earthwork data serves as the baseline. Conversely, if calculations are inaccurate, construction may be delayed due to lack of soil or extra disposal costs for surplus soil may occur.

For example, accurately knowing cut and fill volumes is important in the following situations:

• Planning and managing excavation and filling: If volumes are computed before construction, you can determine how much soil must be hauled from the site or brought in, and accurately estimate the number of dump trucks and schedule.

• As-built management and quality verification: At completion, measure whether the as-built volume matches the design. If shortages or excesses are found, immediate rework or additional import decisions can be made.

• Cost calculation and settlement: Accurate earthwork data is the basis for settling costs and invoicing according to the amount of soil moved. Objective numbers are essential for shared understanding between the client and the contractor.

• Safety management: Properly managing temporary stockpiles and fill quantities helps in assessing collapse risks and planning countermeasures for landslides. Volume control prevents slope instability caused by overfilling.

Traditional earthwork calculation methods and challenges

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

• Manual surveying and calculation: Site supervisors or engineers use tapes and leveling rods to measure the heights and shapes of fills and cuts, then assume several cross sections and calculate volumes by hand using methods like the average end area method. Sometimes estimates are made by experience, such as “roughly X m³ per Y trucks.” However, these methods rely heavily on the operator’s experience and intuition, making it difficult to achieve high accuracy without skilled personnel. Calculations are time-consuming and prone to human error.

• Methods using surveying instruments: Surveyors acquire terrain coordinate data using total stations (TS) or GPS surveying equipment and later compute volumes with CAD software in the office. While accurate, surveying requires multiple people and long hours; on large development sites, a team of two to three may spend days surveying and calculating. Data processing and drawing also take time, so results are not immediate and real-time decisions on site are difficult.

• Rough estimates from machinery or transported volumes: When precise surveying is impractical, the bucket capacity of excavators or dump truck load capacities are used to estimate volumes, e.g., “10-ton dump × X trucks ≒ Y m³.” This provides a rough guideline but does not yield precise quantities.

These traditional methods share common challenges of being time-consuming and lacking real-time capability. Work often must be paused until volume measurement results are available, impeding efficient decision-making. Accuracy and reliability depend on the skills of field personnel, which is problematic amid labor shortages; arranging skilled surveyors for every job is costly. Furthermore, walking around with tapes on steep or unstable ground carries safety risks.

Benefits of automating volume calculations with ICT technologies

In recent years, new earthwork measurement methods leveraging ICT and digital technologies have spread to address these traditional challenges. A representative approach is 3D surveying using drones or 3D laser scanners to calculate volumes. By acquiring high-density 3D data (point clouds) and computing volumes, accuracy and speed of earthwork calculations have dramatically improved.

This makes it realistic to perform earthwork measurements daily instead of about once a week, enabling same-day progress tracking.

• Drone (photogrammetry) earthwork measurement: Small unmanned aerial drones equipped with cameras capture the site from above; software generates a 3D model (point cloud) from multiple photos and computes volumes. Vast sites can be surveyed quickly, and quantities on steep slopes where people cannot enter can be measured safely. Calculating volumes from the obtained point cloud can reduce what used to take several days to a few hours. There are reports of cases where earthwork measurement that took 4 people 7 days was completed by one person’s drone flight in a few tens of minutes when combined with dedicated cloud software. However, drones have operational hurdles such as aviation law restrictions, weather dependencies, and required piloting skills.

• 3D laser scanner measurement: Ground-based laser scanners acquire high-precision point cloud data with laser light, measuring site shapes to millimeter accuracy and enabling accurate volume calculation from point clouds. However, laser scanner equipment is very expensive and requires skilled operation, making daily use by site staff challenging.

While these advanced technologies have greatly improved earthwork management efficiency, there has also been demand for “something easier to use.” Drones and large scanners are effective but difficult to introduce at some sites due to expertise, permits, and cost. Recently, smartphone-based surveying solutions have emerged. By combining a smartphone with dedicated devices and apps, anyone can perform simple 3D measurements and compute earthwork volumes on site.

Easy earthwork management using the cloud

In digital earthwork calculation workflows, using cloud services is also a major key. Previously, survey data had to be handed over via paper drawings or USB, but with cloud integration, site and office stakeholders can share data instantly. Benefits of cloud-based earthwork management include:

• Rapid decision-making through real-time information sharing: As soon as surveying finishes, point cloud data and calculated volume results acquired on site can be uploaded to the cloud. Remote offices can immediately view the site data via the internet, allowing understanding of the situation without being on site. For example, if a site person shares measurement results to the cloud, headquarters construction managers or clients can immediately view numbers and 3D models and provide instructions or approvals. Eliminating data-transmission lag dramatically speeds up construction decisions.

• Accumulation and utilization of survey data: Storing measurement data in the cloud makes history management and progress visualization easy. Past earthwork data can be retrieved later to compare pre- and post-construction terrain. Overlaying design volumes and actual as-built volumes online makes it easy to identify shortages or excesses at a glance. Saving multiple measurement datasets in time series enables remote monitoring of daily construction progress and confirmation that earthwork is proceeding according to plan.

• All team members sharing the latest data: Centralized cloud data management ensures stakeholders always refer to the same up-to-date information. Compared with relying on paper drawings or verbal communication, misunderstandings and transmission errors are reduced, and site-office coordination becomes smoother. This enables not just “measuring and finishing” but an operation of “making measured data useful for everyone,” improving the accuracy and efficiency of site management.

Cloud utilization not only simplifies earthwork management but also accelerates the PDCA cycle for the entire construction project and contributes to quality improvement. Linking earthwork calculation tools with the cloud is becoming an essential element for realizing rational, data-driven construction management.

Utilizing simple surveying with the latest LRTK technology

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

LRTK combines high-precision GNSS positioning data with 3D measurements from the smartphone camera or LiDAR scanner, allowing automatic calculation of earthwork volumes from point clouds acquired on site. Volumes of fills and excavations can be calculated on the spot, and results are immediately displayed on the smartphone screen. Measurement data are also saved and synchronized to the cloud in real time, making it easy to review details on an office PC or share with the team.

LRTK is designed to be intuitive to operate so that people without specialized knowledge can master it with short training. Surveying is completed simply by following the app’s on-screen instructions, enabling non-experts to obtain high-precision point cloud data. Because one person can move and measure, the need to send personnel into hazardous areas for manual measurement is reduced. Steep slopes can be scanned safely from a distance, lowering workload in extremely hot conditions or on poor footing. Its ease of use helps alleviate labor shortages and supports site operations that do not depend on veterans.

For example, even a stockpile several meters high can be accurately measured by walking around it for a few minutes holding a smartphone equipped with LRTK. With the resulting volume, the amount of soil to be hauled by dump truck and deviations from design can be immediately understood, enabling prompt on-site decisions. Where previously work might be suspended while waiting for results or rely on experience-based judgments, LRTK enables a shift to 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 also promotes productivity improvement on construction sites through ICT (so-called “i-Construction”), and the combination of smartphone surveying devices and the cloud is likely to become a new standard for future site management. By introducing these latest tools, the labor required for earthwork calculations can be greatly reduced, accelerating the site’s DX (digital transformation). Take this opportunity to adopt modern technologies for earthwork management and achieve 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 slopes, and fill is the work of forming ground by placing soil. It may be easy to remember that in roadworks or land development, cutting is excavating and removing unnecessary soil, while filling is bringing in and using necessary soil to fill.

Q2. Why does volume change between cut and fill? A. When excavated, soil loosens and contains air, increasing volume; when compacted, density increases and volume decreases. The same soil therefore has different volumes in the in situ state, the excavated loosened state, and the placed-and-compacted state, so volumes differ between cut and fill.

Q3. What methods are there for calculating earthwork volumes? A. Traditionally, cross-sectional drawings are created from surveyed terrain and volumes are calculated by methods such as the average end area method or mesh (grid) methods. More recently, methods that automatically compute volumes from drone photogrammetry or 3D scanner point clouds have become common. In any case, the common point is calculating volume from height differences between a reference surface and the changed terrain.

Q4. What are the benefits of managing earthwork volumes in the cloud? A. Using the cloud allows all stakeholders to share survey data and calculation results in real time. You can check the latest earthwork volumes and 3D models without going to the site, enabling faster decision-making. Centralized data makes historical comparisons and analysis easy, facilitating plan revisions and as-built verification. Accumulated cloud data can also be used for future project planning and client reporting as objective evidence.

Q5. How can I easily measure earthwork volumes on site? A. Even without specialized surveying equipment or advanced skills, recent smartphone-based surveying devices make it easy to measure earthwork volumes. For example, using a smartphone-integrated high-precision GNSS receiver like “LRTK,” you can scan terrain with a phone and automatically calculate fill and cut volumes on the spot. This eliminates the manual surveying and calculation work of the past, enabling anyone to obtain accurate volumes in a short time. What used to take half a day for measurement and calculation can be completed in a few minutes on site with LRTK, and results can be shared immediately. No special qualifications or permits are required, which makes adoption easy.

Q6. What is the difference between drone-based volume measurement and smartphone surveying? A. Drone surveying can measure wide areas quickly, but has constraints such as flight permissions, piloting skills, and weather. Smartphone surveying with LRTK requires no special permits and anyone can measure on site easily, making it suitable for small sites or routine measurements. For very large sites, drones are more efficient. It is best to use both depending on site size and conditions.

Q7. How are swell (L) and compaction (C) rates calculated? A. With the in situ ground quantity set to 1.0 (100%), L (swell factor) is loosened soil quantity ÷ in situ quantity, and C (compaction factor) is compacted soil quantity ÷ in situ quantity. For example, excavating 100 m³ (3,531.5 ft³) of in situ soil, if L = 1.2 then the loosened volume is 120 m³ (4,237.8 ft³). If that 120 m³ of soil is compacted into fill with C = 0.9, the fill volume becomes 108 m³ (3,814.0 ft³). Using L and C values allows conversion between cut and fill volumes. Note that L and C vary with soil type; national guidelines give examples such as sandy soil L = 1.20 and C = 0.90, and cohesive soil L = 1.25 and C = 0.90.