Essential Surveying and Layout Skills in the ICT Era: Leveraging MC Integration and Drone Surveying

Surveying and layout (sokusetsu) refers to the work of accurately transferring points and lines shown on design drawings to the field — the so-called staking out or setting out on construction sites. This is a critical process that determines the quality and accuracy of construction. Traditionally, surveyors performed this work manually using transits, levels, and tape measures. However, in recent years the construction industry has increasingly adopted ICT technologies, and a new construction method called information and communication technology construction (ICT construction) is becoming mainstream. Along with this, the skills required for surveying and layout have evolved significantly. For young construction managers and surveying novices, acquiring surveying and layout skills suited to the ICT era is essential. This article explains, from a practical perspective, the basics of surveying and layout, the skills for integrating with machine control (MC) in ICT construction, and how to utilize drone surveying. Topics include aligning with 3D design data, control point management, data transfer to construction machinery, generation of orthophotos and point clouds, as-built management, and accuracy verification, all explained in language understandable to beginners. At the end of the article, we also introduce the latest tools for simple RTK surveying using a smartphone and a compact GNSS receiver. Let’s look at surveying and layout skills useful on ICT-era sites.

Basics of surveying and layout: transferring the design to the field

On construction sites, “surveying and layout” means reproducing the positions and elevations on the design drawings accurately on site. Concretely, this involves marking the ground or driving stakes at positions for building footprints, road centerlines, widths, elevations, etc., according to the design. For example, installing stakes at the four corners of a building or installing temporary structures such as boards and strings called “chouhari” to indicate elevation and width in roadworks are part of surveying and layout. Surveying and layout work begins by establishing control points (known-coordinate points that serve as site references) and using total stations, levels, tape measures, and the like to set stakes at designated coordinates. What’s important is matching the numbers on the design drawings with the values measured on site. If the layout is off, foundation positions and elevations will be wrong, affecting the entire structure. Therefore, surveying and layout determine the accuracy of the work, and beginners must first understand the meaning and importance of these basic tasks.

In traditional surveying and layout, more than one person was required to set up chouhari and perform leveling, and detailed manual work was needed at each layout point. Experienced craftsmen read drawings and judged on site “this is the location of 〇〇 on the design,” driving stakes accordingly, so the quality of the as-built shape depended in part on the worker’s skill. Also, during layout and construction, assistants guided and checked, making the work manpower- and time-intensive. But today, ICT technology has brought major changes to these surveying and layout tasks.

Surveying and layout evolving with ICT construction

ICT construction refers to methods that use electronic devices and digital data to improve efficiency and accuracy of construction. With the Ministry of Land, Infrastructure, Transport and Tourism promoting “i-Construction,” ICT construction is rapidly spreading across civil engineering and construction sites. One of the core technologies in ICT construction is ICT construction machinery, heavy equipment (bulldozers, excavators, etc.) equipped with GPS and sensors. By referring to 3D design data, these machines can operate automatically or semi-automatically, changing the way surveying and layout are carried out compared to the past.

Previously, chouhari was set up before work and operators (machine drivers) used those marks as references, relying on intuition and experience to cut or fill. Naturally, the accuracy of the as-built depended on the operator’s skill, and in poor visibility such as at night it was difficult to maintain accuracy. With the introduction of ICT construction machinery, chouhari and fine on-site guidance are becoming unnecessary. Monitors are installed in operator cabs showing the current blade position and the difference from the design surface in real time. The operator can work while checking the monitor and, in some cases, the machine automatically adjusts blade height. As a result, high-precision work can be done efficiently with fewer personnel, and safety has dramatically improved (the need for people to guide machines near equipment is reduced, lowering the risk of contact accidents).

Moreover, surveying before and after construction is digitalized in ICT construction. The initial existing terrain can be surveyed by drone or 3D scanner and converted into 3D data, and after construction the finished terrain can be re-surveyed in 3D and overlaid with the design data so that as-built errors can be instantly checked on a PC. In other words, you can “bring the entire site back as data.” This greatly simplifies tasks that previously required manual spot checks of elevations after construction.

The expected benefits of implementing ICT construction include:

• Shortened construction period: Reduced effort for surveying and inspection speeds up construction and shortens overall schedules.

• Cost reduction: Reduced personnel and more efficient operation of machinery lower labor and fuel costs.

• Improved quality and accuracy: Construction based on 3D data achieves accurate as-built results without relying on human intuition.

• Improved safety: Less need to enter hazardous areas for chouhari installation or machine guidance reduces accident risk.

• Improved client satisfaction: High-accuracy construction and shorter schedules increase client trust and evaluation.

While ICT construction has many advantages, maximizing these effects requires on-site engineers to acquire skills to handle digital data and new technologies. The following sections explain the specific skills and knowledge required of surveying and layout personnel in the ICT era.

Ability to align with 3D design data

“Aligning with 3D design data” means matching the 3D design model created on a computer with the actual site coordinate system. In ICT construction, design shapes for roads and development sites are provided as digital 3D data instead of paper drawings. To use this data on site, you must confirm that the coordinates in the data and the site’s survey coordinate system are not offset, and adjust them if necessary.

For example, if the design data is created in a global geodetic lat/long system, the site may need conversion to a national plane rectangular coordinate system. If the designer created the model in an arbitrary local coordinate system, you need to compare it with site control points and move/rotate the entire model to localize it to the site reference coordinates. If this is neglected, even if you load data into machines or surveying equipment, the site may show positions off by meters — a critical error.

The first important step in achieving alignment is verification using control points (known points). If the 3D design data contains known points (for example, positions of existing structures or boundary points), survey those on site and verify whether the coordinates match the model values. If there is a discrepancy, apply an offset correction to the model or set coordinate transformation parameters in the surveying system. Beginners may find this difficult, but essentially it’s about perfectly overlaying the “world inside the computer” with the “real site.” If this alignment is not achieved, all subsequent processes will be affected, so surveyors in the ICT era must have basic skills to understand and handle 3D data coordinate and unit systems.

Control point management and understanding coordinate systems

The foundation supporting surveying accuracy is control points (control points). A control point is a site point assigned accurate coordinates (X, Y, Z) and serves as the starting point for surveying. Surveyors have long said “first establish solid control points on site,” and this holds true in ICT construction. Indeed, with 3D data usage today, control point management becomes even more important.

Key points to keep in mind for control point management:

• Set multiple control points: Ideally at least two control points, and preferably three or more surrounding the site. By surveying between multiple control points (reciprocal observations), you can check for offsets and errors.

• Periodically verify accuracy: Control points can move during construction. Stakes may loosen due to machine vibration or adjacent works, so periodically remeasure distances and elevations between control points and check for differences from previous surveys.

• Unify the coordinate system: Standardize the coordinate system used at each site (e.g., a specified plane rectangular coordinate system) and manage control point coordinates in that system. If the client provides control points, use those as a starting point and compute coordinates for any additional points you establish in the same system. Mixing coordinate systems causes confusion.

• Physical preservation: Mark or protect control point stakes or nails to prevent damage or removal during construction, such as by placing visible signs or protective enclosures and notifying all site personnel. Also, secure backup points as alternatives in case a control point is lost.

Control points are like the origin of the site’s measuring tape. If this origin is off, all subsequent surveying will be off. ICT devices (GNSS and total stations) are also calibrated and set up based on control points. Therefore, treat control point management as “a quiet but the most important task.” Young engineers may find it difficult at first, but learn the procedures for selecting, installing, and observing control points under the guidance of seniors. It is not an exaggeration to say that whoever controls the control points controls the surveying.

Skills for integrating with Machine Control (MC)

Next, we explain integration with machine control (MC). Machine control refers to systems that use GPS and sensors installed on construction machinery along with 3D design data to automatically control the movements of blades and buckets. Systems that merely assist operator judgment are called machine guidance (MG); here we collectively refer to them as ICT construction machinery. To operate ICT construction machinery effectively on site, surveyors need a different skill set than before.

MC-enabled bulldozers are equipped with two GNSS antennas on the blade, and the operator’s monitor displays the machine’s position and the elevation difference from the design surface. The operator simply follows this guidance to achieve high-accuracy finishing even without being a veteran. Advanced MC systems can automatically control blade up/down movement, enabling what can be called “autonomous construction machinery.” For example, when leveling embankment with a bulldozer, the machine automatically adjusts blade height based on the imported design ground model, so the operator only needs to focus on throttle and steering. This allows even inexperienced operators to achieve uniform finishing.

As a surveyor, first and foremost you must provide correct 3D data to the machines. Convert data provided by designers or higher-ups into machine-compatible formats (each manufacturer has proprietary formats) and distribute them to all ICT machines on site. Though cloud-based systems that transmit data to machines are increasingly available, some sites still copy data directly via USB memory. Managing data distribution to avoid omissions or version errors is also the surveyor’s role. If design changes or revisions occur, promptly update the machines with the latest data; otherwise work may proceed using outdated information.

Also important is machine coordinate alignment (calibration). Although the positions of GNSS antennas on machines and the distance from the blade tip to the antenna are pre-set for compensation, field calibration (fine-tuning to site control points) may be necessary. For example, with an excavator, you might need to touch the bucket tip to a control point to align the machine coordinates. Surveyors carry out these procedures in cooperation with the operator. Ensure that the machine-mounted GNSS aligns properly with control points so the monitor displays correct remaining earth quantities and cut/fill positions.

Be aware that ICT machinery is not omnipotent. In areas where GNSS is unavailable (under viaducts, inside forests, tunnels, etc.), machine positioning fails. In such cases you must switch to total-station-based machine guidance or perform conventional manual staking. Surveyors support the site including these complementary measures. Also, surveyors should sample-check as-built results after ICT machine work. Using drone surveys or rovers (mobile GNSS), verify the finished ground elevations at several points against design values and instruct operators to make additional corrections if necessary. In this way, surveyors manage construction accuracy from both digital and analog aspects in the ICT era.

Utilizing drone surveying: orthophotos and point cloud data

Next, we provide practical guidance on drone surveying. Surveying with drones (unmanned aerial vehicles) has rapidly gained attention in civil engineering and construction due to its speed, high accuracy, and safety. By photographing the site from above with a camera mounted on a small drone and analyzing the images with specialized software, you can produce orthophotos and 3D point cloud data. Since data can be acquired across an area from the air, wide-area site surveys that would take a long time by manpower can be completed in a short time.

For example, on large development sites or mountain-area surveys, traditional surveying teams took several days to measure many points. With drone surveying, depending on the flight plan, you can acquire terrain data for the entire site in tens of minutes to about half a day. Processing the captured photos in software first creates an orthophoto. An orthophoto is an aerial photo that has been stitched and corrected to remove distortion so it appears as if viewed from directly overhead. Simply put, it is a mosaic of drone-captured site photos made into a map-like image. Orthophotos have accurate scale and are suitable for measuring distances and areas or overlaying with CAD drawings. The photogrammetry process also generates 3D point cloud data. A point cloud is a collection of many points each with X, Y, Z coordinates, representing the site terrain in three dimensions. By viewing point clouds, you can see ground undulation and structure shapes three-dimensionally and measure elevations or distances at arbitrary locations later in software.

Orthophotos and point clouds obtained by drone surveying can be used in various on-site applications. For example, earthwork volume calculation: conduct drone surveys before and after excavation or embankment, compare the obtained terrain datasets, and automatically calculate cut/fill volumes. This greatly improves the efficiency of progress and quantity management that used to be done manually. Drone surveying also excels at as-built management. As described later, overlaying the completed terrain point cloud with the 3D design model allows visual checking of elevation and shape discrepancies. Or, by displaying design drawing lines transparently over an orthophoto, you can immediately see whether road centerlines or boundaries are misaligned. With a dataset that records the whole site, you can later verify points of concern at your desk such as “was this area constructed according to the design?”

Because of these benefits, drone surveying is being used widely from pre-construction surveys (site condition surveys) to progress management during construction and as-built inspections. Drones are especially effective on large sites or sites with hazardous areas, where rapid and safe data acquisition is critical. They can capture detailed terrain remotely in places humans cannot safely enter, such as landslide sites, balancing safety and quick situational awareness.

However, there are caveats to drone surveying: procedures for ensuring accuracy and legal requirements. For accuracy, it is common to use several ground control points (GCPs) called standard points during image processing. GCPs are easily identifiable points placed on the ground and measured precisely, which are tied to the images in software processing to improve overall accuracy. Measuring GCP coordinates requires high-accuracy GNSS receivers or total stations, but as described later, simple RTK devices make it relatively easy for beginners to measure them. Recently, RTK drones with onboard RTK-GNSS have become common, enabling photo geotagging at centimeter-level (half-inch-level) accuracy during flight. Using such equipment, drone surveying can achieve accuracy comparable to conventional ground surveys (within a few centimeters (within a few inches)).

Legally, in Japan since 2022 some flights require a drone pilot license (unmanned aircraft operator skill certification). For flights that meet certain conditions — flying over third-party property, beyond visual line of sight over populated areas, or at night — qualifications and permission applications to the Ministry of Land, Infrastructure, Transport and Tourism are required. Flying in small, obstacle-free sites is not very difficult, but flights in urban areas or near airports may be prohibited or restricted. Note that drones are not something anyone can immediately fly without preparation. Obtain necessary qualifications and implement safety measures, and operate within the rules.

As-built management and accuracy verification with drone surveying

After performing construction using drones and ICT machinery, conduct as-built management and accuracy verification. As-built management involves confirming and recording whether completed structures and terrain match design shapes and dimensions. In the ICT era, as-built management goes beyond manual spot checks against paper drawings and enables comprehensive checking using 3D data.

For example, in roadworks, you can create point clouds of the finished surface via drone photogrammetry or terrestrial laser scanning and overlay them with the design 3D model (BIM/CIM model) to check quality. Creating colored deviation maps from point cloud data visualizes deviations from the design surface with color gradations. You can immediately identify that one location is +3 cm higher than the design and another is −2 cm lower, enabling prompt corrective work if nonconformances are found. Using point clouds you can also check longitudinal and cross-sectional shapes at arbitrary locations. Where previously representative sections were measured, point clouds allow you to cut sections later for any “areas of concern” and examine cross-sections. This eliminates measurement omissions and enables comprehensive verification of as-built conditions.

Accuracy verification also requires confirming the accuracy of the acquired data itself. For verifying point cloud accuracy from drones, use check points called verification points. Precisely measure the coordinates of several points on site in advance and compare those coordinates with the corresponding points on the point cloud to calculate errors. If horizontal and vertical errors fall within acceptable ranges (for example, within 5 cm), they are acceptable. If not, adjust processing software or perform additional field surveys to correct them. Similarly, when construction is performed with ICT machinery, perform cross-checks at key locations for assurance. Even with machine-controlled embankment, verify elevations manually at several locations to validate machine control accuracy. If no large discrepancies are found, reflect the results in the as-built records; if discrepancies are found, perform remediation and re-verify.

Thus, even using digital technology, maintaining a posture of confirming accuracy with your own eyes and hands is essential. Final as-built documentation should state deviations from design values and measurement accuracies. To convince clients, organize and present evidence data (point clouds and orthophotos) and verification results. Inspection methods have advanced with ICT, but the basics remain “correct control points and verification,” and the hybrid approach of analog and digital accuracy assurance is unchanged.

Starting simple RTK surveying with a smartphone and small GNSS: Introducing LRTK

Finally, we introduce RTK surveying using a smartphone and a compact GNSS receiver, a new on-site surveying style gaining attention. Recently, combining high-performance smartphones with ultra-compact RTK-GNSS receivers has made it possible to turn a smartphone into a high-accuracy surveying device. A leading example is LRTK (compact RTK-GNSS device). By attaching a small dedicated GNSS receiver to an iPhone or iPad and launching an app, centimeter-level positioning becomes possible. Tasks that previously required high-precision GNSS equipment costing millions of yen can now be performed with a smartphone that fits in your pocket, drawing quiet interest among field practitioners.

Using LRTK, single-point positioning (point surveying) on site is remarkably simple. For example, mount the smartphone and receiver on a dedicated pole, place the tip at the point to be measured, and press a button. Latitude, longitude, and elevation are calculated in real time, and conversions to the plane rectangular coordinate system and geoid height corrections are automatically applied. Point names and timestamps are recorded automatically and notes can be attached. Measured data can be uploaded to the cloud with one tap and instantly checked from an office PC. In other words, survey data obtained on site can be shared with the office and used in real time.

Accuracy is reportedly comparable to first-class surveying instruments. LRTK uses Japan’s satellite positioning augmentation services (such as QZSS CLAS signals), and nominal errors are around 1–2 cm horizontally and about 3 cm vertically. In actual tests, 30-second averaged measurements have been reported to fall within a few millimeters (a few hundredths to a few tenths of an inch), showing accuracy comparable to general GNSS surveying instruments. What’s revolutionary is that it is far lower cost and easier to use than conventional equipment. Dedicated apps also include AR features that project acquired high-accuracy coordinates and 3D models into the real world. For example, you can overlay a building layout model on your smartphone screen and intuitively mark stakeout positions. It’s truly a versatile tool that can cover surveying and as-built confirmation with one smartphone.

Introducing such smartphone surveying devices to a site makes a one-device-per-person surveying style feasible. With easy RTK terminals like LRTK, young engineers can perform simple surveys with their own phones. Machine operators can measure as-built results themselves, and construction managers can quickly confirm dimensions on site without calling a specialized survey team. For construction sites struggling with manpower shortages and efficiency issues, this is a powerful advantage. We recommend trying it on site to experience its convenience firsthand. It will likely change the impression that “surveying seems difficult” and amaze you with a new digital surveying experience.

Summary: Surveying and layout in the ICT era require advanced skills that connect data and the field, but the essence remains the same as before: “accurately reproducing design on site and accurately digitizing the site.” Understanding 3D design data, strictly managing control points, accurately transferring data to MC machinery, utilizing drone surveys for wide-area measurement, and adopting easy RTK tools like LRTK together can dramatically improve site productivity. Young professionals should not overthink it; take small steps to tackle digital surveying. In future construction sites, the skill of surveying and layout may well determine project success or failure. Use this article as a reference to acquire essential surveying and layout skills for ICT construction and grow into an immediate asset for tomorrow’s sites!