Smartphone Surveying Changing Preliminary Design Methods: The Latest Trends in On-site Efficiency

Introduction: Speed and On-site Responsiveness Required in Preliminary Design

In civil infrastructure, preliminary design (the early-stage design) is a critical process that determines the overall direction of a project and the ballpark cost. Typically, at this stage, design proposals must be compiled and presented to stakeholders within a short timeframe. Therefore, speed and the ability to respond to on-site conditions are required. For example, when sudden design changes or additional investigations become necessary, whether the site conditions can be quickly understood and reflected in the design can determine the project's success or failure. Recently, DX (digital transformation) in the construction industry has advanced, accelerating efforts to strengthen coordination between the field and design. One approach attracting attention in this context is smartphone surveying. This article explains in detail the efficiency trends smartphone surveying brings to preliminary design and the innovative methods for earthwork quantity calculation (volume calculation).

Importance of Understanding Earthwork Quantities in Preliminary Design

In infrastructure design, understanding earthwork quantities is an extremely important point. In civil works, the volumes of earth and sand directly affect the scale and cost of construction—such as fill and cut volumes in site formation, embankment volumes for road construction, excavation and backfill volumes for water and sewer installations, and excavation volumes for structural foundations. If earthwork quantities can be accurately understood at the preliminary design stage, cost estimate accuracy improves and it becomes easier to judge the validity of the design. Conversely, underestimating earthwork quantities can lead to major design changes or budget overruns in later stages. For instance, if the amount of earth to be moved is greater than initially assumed, additional hauling costs or securing disposal sites may become necessary, impeding overall project progress. Thus, in preliminary design it is required from an early stage to grasp “how much earth will be moved.” However, a major challenge has been that detailed survey data are often unavailable in the early phases.

Issues with Conventional Methods: Dependence on Surveying and Estimation Errors

In conventional preliminary design, it was common to rely on surveying to obtain local terrain information. Conducting a full-scale survey reveals accurate ground elevations and shapes, but requires specialized surveying staff and equipment, which takes time and incurs costs. It is difficult to carry out detailed surveys from the initial stage, so in many cases earthwork quantities were estimated using existing topographic maps and elevation data (for example, maps or digital elevation models from the Geospatial Information Authority of Japan). However, these materials are not always up to date or highly accurate, and they may show coarse contour lines at 5 m (16.4 ft) and 10 m (32.8 ft) intervals or fail to reflect terrain altered by past earthworks. As a result, estimation errors of even double-digit percentages are not uncommon. For example, an embankment volume calculated assuming flat terrain might differ significantly in reality due to accumulated subtle undulations.

Furthermore, conventional methods have issues of personnel and logistics. Surveying with a total station typically requires a two-person team at each measurement point, necessitating coordination of busy surveyors’ schedules and on-site time allocation. Even for small-scale site investigations, situations often occurred where “design cannot proceed until the survey team arrives.” Consequently, designers were often forced to rely on heuristics and safety factors for earthwork estimates without sufficient on-site detail, leading to reduced accuracy. To summarize the issues of conventional methods:

• Survey cost and time: Detailed surveys take time and money, making them hard to carry out casually at the preliminary stage

• Coarse data: When substituting existing materials, low resolution can miss terrain details

• Risk of reduced accuracy: Quantity calculations based on uncertain information are prone to large errors

• Reduced responsiveness: It is difficult to respond quickly to on-site changes or compare alternatives (waiting for surveys)

As a means to solve these issues, smartphone surveying has attracted attention in recent years.

What Is Smartphone Surveying? An On-site Earthwork Measurement Tool Anyone Can Use

As the name suggests, smartphone surveying is a simplified surveying method using a smartphone. By simply installing a dedicated app on a smartphone, you can use the camera and sensors (accelerometer and gyro, and on recent high-performance devices even LiDAR sensors) to measure the on-site situation. The biggest attraction is that measurements can be taken on-site “by anyone,” “immediately,” and “right there” without special surveying equipment.

Many smartphone surveying apps apply AR (augmented reality) technologies, displaying virtual survey poles or tape measures over the live camera view for operation. For example, by pointing the smartphone and placing virtual points on the ground, you can measure distances and elevation differences or automatically calculate the area or volume of an enclosed region. No difficult operation is required—the intuitive UI guides users, so technicians or site workers without surveying expertise can operate them. Also, because everything is done with a single smartphone, it is easy to display measurement results as graphs on the spot, save numeric values, and share them by email or cloud. This enables a process that used to be “survey → office data processing → design reflection” taking days to be completed with a short on-site task.

Especially for earthwork measurement, smartphone surveying apps incorporate various features. There are modes to calculate volume by indicating the bottom and top extents of fills or excavations on the screen, modes to obtain cross-sections on-site and compute cross-sectional areas and fill volumes, and modes to estimate the area and earthwork within irregular polygonal regions enclosed by three or more points—tools tailored to different purposes. With just a smartphone, one person can obtain sufficiently necessary earthwork data, solving the long-standing problem of data shortage at the initial design stage.

From Point Clouds to Earthwork: The Relationship Between Smartphone Surveying and Estimation Accuracy

An advanced aspect of smartphone surveying is that it can readily obtain not just simple point measurements but three-dimensional point cloud data. A point cloud is data that plots numerous measured points in 3D space and can represent the shape of terrain or structures in detail. While conventional surveys represented terrain with elevation points on a distant grid or a few cross-section lines, point cloud data contain surface and volumetric information, producing a precise model that captures subtle surface undulations.

On smartphones equipped with LiDAR scanners (for example, the latest iPhones or iPad Pro), holding up the camera and walking around allows continuous acquisition of close-range point cloud data. Even without LiDAR, photogrammetry techniques can reconstruct shapes from camera images; in either case, a 3D model of the current terrain can be generated in a short time. The flow from the obtained point cloud to earthwork calculation is as follows:

• Acquisition of the current point cloud: Scan the target area with a smartphone to obtain a point cloud of the local surface, fills, and deposits.

• Comparison with a reference surface: Set the reference surface assumed in the design (for example, the designed finished elevation or a known ground surface) and overlay it with the point cloud data.

• Computation of differential volumes: Automatically calculate fill and excavation volumes from elevation differences between the point cloud and the reference surface. Because point cloud data consist of a very large number of points, the differential volume calculation can produce accurate values that include fine undulations.

Thus, smartphone surveying’s strength is the ability to instantly calculate earthwork quantities using the acquired point cloud data. Regarding accuracy, recent validation results report cases where volume calculations from quick smartphone scans were within a few percent of the results obtained by expensive laser scanners. Of course, errors vary depending on environmental conditions and operator skill, but the potential to meet the accuracy required at the preliminary design level (generally in the range of a few percent to the low tens of percent) has been demonstrated.

What matters is the statistical advantage of point clouds. Even if individual points have somewhat large errors, averaging over many measurement points yields an accurate representation of the overall shape. For example, deriving an average cross-section from a point cloud of several thousand terrain points obtained by smartphone will cancel out some noise and accurately capture the overall terrain trend. This point cloud approach prevents the “overlook due to few measurement points” typical of conventional methods and provides data that directly leads to improved preliminary design accuracy.

Case Studies: Single-person Measurement and On-the-spot Differential Volume Calculation

Now let's look at concrete examples of how smartphone surveying is actually being used. In a preliminary design for a road improvement project, it was necessary to estimate the cut volume of a small hill along the route. Conventionally, one would produce cross-sections from a schematic longitudinal profile and calculate volumes using the average cross-section method, but in this case the design engineer took just a smartphone to the site and performed a quick measurement.

The engineer scanned the hillside with the smartphone while walking around, obtaining a point cloud of the current terrain. On the smartphone app, the engineer overlaid a planned road elevation (design elevation) as a provisional plane and color-coded the elevation differences with the current terrain. This immediately showed which parts needed how much excavation to reach the design elevation, and the app automatically calculated the differential volume (required excavation volume) on the spot.

The entire process from field measurement to volume calculation took only a few tens of minutes, and there was no need to return to the office for PC-based analysis. Because one person could measure and obtain earthwork quantities on-site, the design team was able to compare earthwork quantities for multiple route options within the same day and quickly select the optimal plan.

In another example, smartphone surveying was used to manage fill volumes of stockpiles at a site. A construction manager scanned a pile of spoil alone with a smartphone and checked the change in volume since yesterday (how many cubic meters were hauled away) on the spot. This enabled flexible adjustment of truck numbers and heavy equipment allocation according to daily progress, contributing to efficient construction planning.

As these examples show, smartphone surveying brings the field the responsiveness of “measure when needed and get results immediately.” Earthwork that used to be checked with cross-sections and quantity calculation sheets can now be visually grasped on-site and immediately quantified, enabling consistent data sharing and decision-making from planning through the field level.

Toward Field-driven Design: The Transformation Brought by Smartphone Surveying

The spread of smartphone surveying is transforming the conventional office-centered design process into a field-driven design. Traditionally, designers worked in the office poring over drawings while the field followed the provided drawings. But by using smartphones—highly capable devices that can be carried to the field—field staff and designers can acquire data on-site and immediately reflect that feedback in the design. In other words, the field becomes an important input source for design.

The benefits of this trend are numerous. First, because design adjustments can be based on real on-site conditions, the gap between design and construction narrows. If field personnel collect data via smartphone surveying from the design stage and share it, troubles such as “things don’t go as drawn” or “quantities are insufficient” during construction are less likely to occur. Also, rapid comparison of multiple options becomes easy. Previously, each option required surveying → drawing production → quantity calculation, but by simulating based on smartphone surveying data you can compare alternatives in a short time. Field constraints and terrain considerations are visible from the start through point cloud visualization, enabling early handling of issues that might not be noticed at the desk.

Additionally, communication activation is a major change. If field-measured data are shared immediately via the cloud, clients, designers, and contractors can discuss using the same up-to-date information. For example, municipal staff and design consultants can conduct a site visit while measuring with a smartphone and discuss estimated construction costs on the spot based on the results. This is truly a “field-led” design style and aligns with the philosophy of i-Construction promoted by the Ministry of Land, Infrastructure, Transport and Tourism.

In short, smartphone surveying is not merely a tool advancement but is promoting innovation in the design workflow itself. With raw field data directly reflected in design, the traditional separation between field and office is becoming integrated. This transformation enables simultaneous acceleration and accuracy improvement of design and strengthens on-site responsiveness.

Conclusion: A New Preliminary Design Workflow Starting with a Smartphone

We have seen the efficiency and accuracy improvements smartphone surveying brings. Finally, let’s organize the new preliminary design workflow. Conventionally, the order was “plan based on existing materials → later incorporate survey data → revise design,” but going forward the following flow may become mainstream:

• Start with a field scan: An engineer visits the project candidate site and scans the terrain with a smartphone, obtaining up-to-date as-built data from the initial stage.

• Preliminary design in real time: Based on the point cloud and survey data acquired on-site, consider preliminary design options on the spot. Confirm earthwork and elevation differences while deciding the design direction.

• Immediate feedback: Check differences between provisional designs and current conditions on-site (for example, required additional fill or interfering terrain features) and revise the design as necessary.

• Data sharing and consensus building: Share measurement data and study results with stakeholders via the cloud. Achieve early consensus with clients and other departments based on common understanding.

• Transition to detailed design: Because high-accuracy data are already available in the preliminary stage, subsequent detailed design can begin smoothly. In some cases, point clouds from the preliminary stage can be reused for detailed design or CIM models, reducing duplicated work.

This new workflow, where “field measurement is the starting point,” eliminates the initial information bottleneck and enables a lean design process. As a result, clients receive faster and more reliable plan proposals, and designers and consultants gain improved work efficiency and differentiation from competitors. For contractors, quantity estimators who measure the site themselves and obtain high-accuracy quantities can use that information for bidding strategy and construction planning.

Smartphone surveying, which dramatically enhances the speed and on-site responsiveness of preliminary design, is attracting industry attention as the latest trend. The learning curve for the technology is low, so small municipalities and SMEs can adopt it easily, and bottom-up field-driven design reform is expected to advance. Why not consider trying a new design workflow that leverages smartphones?

Bonus: Recommended Start to Simple Smartphone Surveying with LRTK

For those who want to try smartphone surveying, one recommended solution is LRTK. LRTK is a small RTK-GNSS receiver attached to a smartphone that turns a phone into a survey instrument with centimeter-level accuracy (half-inch accuracy). By mounting it on an iPhone and using a dedicated app, anyone can easily obtain high-precision positioning information and point cloud data. For example, with LRTK you can scan a site with a smartphone that fits in your pocket, and have distance, area, and volume measurements performed automatically in the cloud. The acquired point cloud is tagged with global coordinates (absolute coordinates), making comparison with design drawings and integration with other survey data smooth.

LRTK’s strengths are that a dedicated high-precision GNSS greatly reduces positioning errors of the smartphone and that it offers one-stop convenience from measurement to data sharing. In practice, you can upload field-scanned data directly to the cloud and have an office colleague immediately view it in a web browser. LRTK was developed with the goal of one smartphone surveying device per person, and both the device and app are designed to be intuitive and field-oriented.

To experience the efficiency improvements of preliminary design through smartphone surveying, it is best to start with small field trials or internal proofs of concept. LRTK has a low initial introduction barrier and is said to be reasonably priced compared to conventional surveying instruments. If interested, check the [LRTK official site](https://www.lrtk.lefixea.com/lrtk-phone). With a smartphone and LRTK in hand, anyone can start “simple smartphone surveying” today. Use cutting-edge tools to experience the new standard for preliminary design.