The Practical Power of Preliminary Quantity Design Seen in Field Cases

Introduction: Can quantity design change the field?

In civil engineering sites, the preliminary quantities calculated at the design stage are a critical factor that can influence the entire project. If quantities such as the volume of earthworks required, slope surface areas, and the lengths of water and sewer pipes are accurate, both owners and contractors can proceed with confidence. However, large errors in preliminary quantities can lead directly to cost overruns, design changes, and even loss of trust among stakeholders. In fact, in recent years some municipalities have begun trialing a “preliminary quantity design method” that uses preliminary quantities at the initial design and finalizes them after contract award (https://www.pref.chiba.lg.jp/suidou/kyuusui/gaisansuuryou.html). This approach aims to simplify early-stage quantity calculation while enabling rapid procurement, but ensuring the reliability of the preliminary quantities themselves remains a key issue. That is why there is increasing demand for new technologies that improve the accuracy, speed, and reliability of quantity design.

Recently, new technologies that dramatically enhance the accuracy, speed, and reliability of this quantity design have begun to be introduced on-site. This article examines how the “practical power” of preliminary quantity design changes the field through concrete case studies in land development, slope work, and water/wastewater works.

Case 1: Earthwork volume accuracy in development planning determines procurement decisions

This occurred during the planning stage of an industrial park development in a suburban area. The owner, a municipality, planned to balance cut and fill as much as possible to avoid exporting surplus soil off-site. However, there were concerns about the earthwork volume calculations in the basic design produced by conventional methods. Because the terrain was inferred from a limited number of survey points, there was a risk of discrepancies between the estimated and actual cut and fill volumes. If a large amount of unexpected surplus soil were generated due to a misestimate, additional transport costs and schedule delays would be unavoidable. Faced with the procurement decision, the municipal officer worried, “Is this quantity really reliable?”

As a new method, detailed 3D surveying using drone aerial photography and RTK-GNSS was adopted. The entire planned construction area was flown by drone to acquire high-precision point cloud data. The cut-and-fill volumes calculated from that point cloud were far more accurate than the conventional estimates, differing from the initial plan by only a few percent. For example, while conventional methods raised concerns about errors of more than 10% in earthwork volumes, drone surveying has been reported to achieve as-built accuracy of ±5 cm (±2.0 in) and calculated earthwork volume errors within ±5% in some cases ([Japan Federation of Construction Contractors “Productivity Improvement Casebook 2018”](https://www.nikkenren.com/sougou/seisansei/pdf/seisan_all_2018.pdf)). By obtaining such high-precision quantity data, the municipality was able to proceed with procurement as planned with confidence. As a result, there were no major design or contract changes during construction, and the project progressed smoothly.

Case 2: Underestimation of sprayed slope area — a mistake prevented by AR visualization

In a steep slope protection project, the sprayed concrete surface area had been underestimated in the initial design. Because the design drawings simplified the slope geometry, they failed to fully reflect the actual undulations, meaning the required sprayed area could be larger than estimated. Had materials been prepared according to the design quantities, a shortage could have occurred during construction, leaving parts of the slope unprotected.

This mistake was prevented in advance through the on-site use of AR (augmented reality) technology. When the construction manager held a tablet over the slope and overlaid the designed spray coverage model onto the live view of the slope, the uncovered areas became immediately obvious. Previously, the only option was to visually compare drawings with on-site conditions, which could allow subtle oversights; AR’s intuitive “visualization” made quantity errors easy to detect. The team promptly revised the design and arranged for the additional materials needed. As a result, the slope was fully protected as planned without rework or additional orders after construction began.

*AR (augmented reality): a technology that overlays digital information such as 3D models onto camera-captured real-world imagery. In civil engineering, it is increasingly used for visualization of design drawings and buried utility locations.*

Case 3: Point cloud analysis helped avoid redesign of water and sewer pipelines

In a municipal replacement project for aging water and sewer pipes, issues that could not be fully captured by conventional 2D drawings were lurking. The initial design set the new pipe route based on old drawings, but discrepancies with actual site conditions meant there was a risk that design changes would be required during construction.

Point cloud analysis made a major contribution to solving this problem. The team used laser scanners and high-precision photogrammetry to acquire detailed 3D point cloud data of the terrain around existing pipelines, including inside manholes. By integrating the obtained point cloud into a CIM (civil information model) and overlaying the 3D model of the new pipe, the analysis revealed that the initial design would interfere with existing structures in some sections. For example, point cloud data showed that other buried utilities were located very close to the planned route of a sewer pipe, and that the design-specified depth would not provide adequate cover soil thickness over the pipe.

In response to this finding, the design team revised the route and depth of the new pipeline early on. Had the project proceeded based only on conventional drawings without point cloud analysis, unexpected collisions or exposure of buried utilities could have been discovered only during excavation, potentially leading to major design changes and schedule delays. This case, in which simulation based on point cloud data identified risks in advance and prevented redesign, left a strong impression on the stakeholders regarding the usefulness of digital technologies.

Moreover, in recent years tools have been developed that project the location information of acquired underground utilities onto the site via AR so that anyone can easily confirm “invisible obstacles.” For example, Shimizu Corporation developed a tablet-based system to visualize buried utilities that overlays water and sewer drawings onto GNSS-positioned coordinates, helping prevent damage during excavation and improving construction planning efficiency (from the Cabinet Office “Michibiki” official site: https://qzss.go.jp/usage/userreport/shimz_170306_1.html). Combining point cloud data and AR in this way is likely to dramatically improve the accuracy and safety of underground infrastructure work.

Technical background: Point clouds, RTK, and BIM create a new norm for quantity design

Backing the above cases are digital foundations that have attracted attention in recent years: point cloud data, high-precision positioning (RTK-GNSS), and BIM/CIM. Traditionally, preliminary quantity estimation relied on drawing dimensions and empirical rules. Now, however, deriving quantities from detailed digital representations that fully digitize the site is becoming the “new normal.”

Point cloud surveying technology (3D measurement using laser scanners or drone photogrammetry) acquires the terrain and structure surfaces as a high-density collection of points (point clouds). This allows volumes and surface areas that were previously estimated from visual judgment or partial survey points to be calculated directly from measured data. The precision and efficiency have improved dramatically over conventional methods. One construction DX article even states that “point cloud technology can reduce work time by up to 50% and improve surveying accuracy by more than tenfold” (from an explanatory article on construction DX). Because point clouds can measure large areas in a short time, they cover all the information needed for quantity design—from development earthwork volumes and slope shapes to the positional relationships with existing structures.

The spread of RTK-GNSS (real-time kinematic satellite positioning) is further accelerating point cloud utilization. By using GNSS receivers compatible with RTK, point cloud data and photos acquired on-site can be tied to world coordinates (absolute coordinates), with measurement errors kept to a few centimeters or less. This makes it possible to overlay design coordinate systems and on-site measurement data precisely. Applications such as comparing design models and point clouds for as-built management to calculate difference volumes, or accurately overlaying digital information on-site for AR display, become straightforward. Not only expensive surveying equipment, but also products that achieve cm-level positioning by attaching a small GNSS receiver to a smartphone and performing point cloud scans are now emerging, making it easier to obtain high-precision data.

The advancement of BIM/CIM should not be overlooked. BIM originated in the building sector as an information management technology based on 3D models and is being applied to civil engineering as CIM. Creating 3D models from the design stage to automatically calculate quantities and costs and to perform construction-stage simulations dramatically improves project-wide visibility. The Ministry of Land, Infrastructure, Transport and Tourism is promoting full-scale BIM/CIM adoption in public works and standardization of 3D design data with a target of 2025 ([MLIT 2025 BIM/CIM principle application](https://www.archifuture-web.jp/headline/480.html)), and information sharing among stakeholders and rapid quantity adjustments at the time of design changes—difficult with conventional 2D drawings—are becoming commonplace. While preliminary quantities have often been regarded as “mere estimates,” combining BIM/CIM with point clouds and RTK now makes it entirely possible to understand quantities at almost construction-level accuracy from the basic design stage. A new norm in quantity design is truly emerging.

The value of “accuracy” from the perspectives of management and engineers

Improving the accuracy of quantity design matters not only to on-site engineers but also to management. Accurate quantities are not just numbers; they form the foundation that enhances overall project reliability. Traditionally, when errors in design quantities caused budget overruns or schedule delays, a great deal of effort was spent on adjustments, and stakeholders were burdened with coordination and additional negotiations. Conversely, if high-accuracy quantities can be known from the preliminary stage, unnecessary rework can be avoided and project transparency improved. With the chronic labor shortage in the construction industry, reducing rework and achieving reliable outcomes with minimal effort makes improving quantity accuracy an unavoidable task.

What specific value does improved accuracy deliver? Let us organize the benefits from the viewpoints of management and field engineers.

• Management benefits: Reduced project-wide risk (avoiding budget overruns and schedule delays), higher decision-making certainty during planning, easier fulfillment of accountability to owners and residents, reduced internal coordination when additional costs occur, and more. High-accuracy quantities provide reliable data for managerial decision-making and strengthen trust both inside and outside the organization.

• Field engineer benefits: Less extra work dealing with design changes and additional tasks, enabling focus on core responsibilities; improved construction quality (fewer construction errors thanks to appropriate material quantities); improved safety (planned construction proceeds without unexpected shortages or excesses); and personal skill development (acquiring knowledge suited to the digital era through use of new technologies). Higher quantity accuracy makes work easier for engineers and contributes to their professional pride.

Accuracy-backed quantity design is, in a sense, a “guarantee of peace of mind” for a project. For managers it is a navigational compass that stabilizes planning decisions; for field engineers it is a reliable tool to carry out safe and efficient construction.

Conclusion: Field trust begins with quantity accuracy

As shown above, improving the accuracy of quantity design even at the preliminary stage leads to smoother site operations and greater reliability. Accurate earthwork volume calculation supports appropriate procurement decisions in development planning, AR-based visualization prevents construction mistakes in slope work, and point cloud analysis helps avoid unnecessary redesign in pipeline projects. A common thread across these cases is that improving quantity accuracy generates peace of mind on-site and becomes the driving force that builds trust among stakeholders.

With advancing technology, the era of “preliminary estimates can be a bit off” is coming to an end. Actively leveraging digital technology to secure high-precision quantity information from the early stages will become the new norm for construction projects. A focus on accuracy may seem unglamorous, but that accumulation builds substantial trust and sustains field operations. Field trust begins with quantity accuracy—keeping this phrase in mind, we should pursue robust preliminary quantity design in our daily work. It is not an overstatement to say that the accuracy of preliminary quantity design can determine a project’s success or failure.

Bonus: The first step to becoming “practically capable” at preliminary quantity design with LRTK

Even if you want to practice advanced quantity design, you might feel that specialized equipment and software are too high a hurdle. In that context, a recently introduced solution called LRTK is attracting attention as a tool that easily enables simplified surveying, point cloud acquisition, and AR proposals. LRTK consists of a small GNSS receiver that attaches to a smartphone and a proprietary app, turning the phone into a high-precision all-purpose surveying device. Even without specialized knowledge, by walking around the site holding a smartphone you can scan surrounding 3D point cloud data in about 1 minute and automatically calculate soil volumes and areas with errors of a few cm (a few in) on the cloud. The acquired point cloud and 3D models of design drawings can also be displayed in AR on-site and shared with stakeholders. For example, if buried pipes are scanned in advance and projected via AR during construction, “invisible obstacles” can be visualized and construction can proceed safely.

With easy-to-use tools like LRTK, you can start practicing “practically capable” preliminary quantity design today. Even on small sites, tasks formerly outsourced to surveying companies can be performed in-house in a short time, enabling proposals and decisions based on high-accuracy quantity information. Digital technology is a tool; whether we wield it effectively on-site is up to us. As a familiar first step, why not challenge yourself with smart quantity design using LRTK?