Streamline As-Built Management: Accelerate On-Site DX with 3D Surveying and RTK

Table of Contents

• Introduction

• The Importance of As-Built Management and Traditional Challenges

• DX for As-Built Management Using 3D Surveying (Point Clouds)

• What Is RTK Surveying?

• Simple Surveying Expanded by Smartphone × RTK

• What Is Simple Surveying with LRTK?

• Effects of Smart Surveying on the Field

• Conclusion: Accelerate On-Site DX with Smart Surveying

• FAQ

Introduction

In recent years, “construction management DX (digital transformation)” aimed at improving efficiency and quality on construction sites has been accelerating. Amid chronic labor shortages and the need to respond to workstyle reforms, there is an active movement to reassess inefficient on-site work using ICT technologies. Among these, the smartening and digitization of as-built management (dekigata kanri) is attracting particular attention. As-built management refers to the important process of verifying and recording whether the shapes and dimensions of completed structures and land conform to the design drawings. Especially in public works, proof that the as-built conforms to the standards set by the client (such as local governments) is required, becoming a prerequisite for inspection approval and handover. As-built management is truly the foundation of construction management and a key to ensuring quality.

At the same time, digital technologies are making inroads into as-built management. By combining smartphones, 3D surveying data, and high-precision positioning with RTK, it is possible to dramatically improve the efficiency of as-built management that previously required much manpower and time. This article explains the latest as-built management methods using 3D surveying and RTK. From the challenges of conventional methods to the changes brought by the latest technologies, and examples of using the new technology LRTK that supports the field, we present the information in an easy-to-understand way. The content is useful not only for site agents and construction management engineers who work on quality control daily, but also for those promoting ICT in construction or municipal staff who commission works. If you are even a little interested in on-site DX, please read to the end.

The Importance of As-Built Management and Traditional Challenges

The purpose of as-built management is to confirm that the constructed object is finished according to the design documents and to correct any defects. Especially in public infrastructure projects, the results of as-built management determine the pass/fail of quality inspections, making it an unavoidable important task for field technicians. However, there have been several challenges with traditional as-built management methods. The main issues are summarized below.

• Manual measurement inefficiency: In traditional mainstream as-built management, personnel measure the dimensions of structures point by point using tape measures, staffs, and levels, and check the differences against the design values. For example, in road works, after completion the width, thickness, and elevation of the pavement are measured at many locations to verify conformity to standards. This method requires many people and time, and the number of measurable points is limited, placing a heavy burden on the site. In large sites, as the number of measurement points increases, more man-hours must be allocated to surveying plans, and it is not easy to handle with limited resources.

• Risk of limited measurement points: Manual measurement that can only be done where people can enter has physical limits. Dangerous heights, narrow spaces, or locations that will be buried and become invisible after construction cannot be sufficiently measured, revealing the weakness of being able to measure only at points. Even if key dimensions have no problems, if out-of-spec construction occurs in hard-to-see locations, it may be overlooked. In practice, it is not uncommon for later inspections to point out that “it is not as drawn,” forcing hurried corrective work.

• Human errors and omissions in records: The results of manual measurements were noted on-site and then transcribed into drawings and tables back at the office. During this process there is a risk of human error such as writing numbers incorrectly or forgetting records. In busy sites, omissions such as forgetting to photograph buried items are also common. Reinforcement or underground buried items that become invisible after completion cannot be certified for quality unless photographic records are kept during construction; discovering missing photos can lead to the worst-case need to redo work, placing great pressure on site staff.

As described above, traditional as-built management required considerable work time and personnel, and suffered from variability in accuracy due to biased measurement points and human error. Recently, however, “as-built management using 3D point cloud data” has attracted attention as a trump card to solve these problems.

DX for As-Built Management Using 3D Surveying (Point Clouds)

With advances in surveying technology, 3D point clouds—digital records of the real world—are beginning to be used in practice. Point cloud data are countless measurement points (a collection of points) obtained by laser scanners or photogrammetry, representing space as a dense collection of points. Using point clouds allows non-contact, wide-area measurement of the shape of construction sites at once, and enables digital measurement of dimensions at any location afterward. With the momentum of *i-Construction* promoted by the Ministry of Land, Infrastructure, Transport and Tourism, point cloud measurement for as-built management is becoming the “new normal” in the civil engineering and construction industry. In fact, the ministry has prepared guidelines such as the “As-Built Management Procedure (Draft) Using 3D Measurement Technology” to encourage the introduction of 3D technology on sites.

Using 3D point clouds makes it possible to detect small unevenness and shape variations that were previously overlooked. Because structures are scanned over their surfaces, not just at key points, comprehensive as-built verification without gaps or omissions becomes possible. Moreover, since the acquired data are digital, they are easy to share among stakeholders, and progress and quality can be checked remotely via the cloud. This can simplify supervisory inspections and greatly reduce the work of organizing as-built drawings and photos.

Recently, such point cloud measurement can even be done with a single smartphone. The latest iPhone and iPad models are equipped with simplified LiDAR scanners and high-performance cameras, enabling site personnel to perform 3D scanning themselves on site. However, a standalone smartphone typically cannot easily append absolute position information (latitude, longitude, elevation) to the acquired point cloud data, nor can it achieve sufficient absolute accuracy. The solution is to add RTK positioning capability to the smartphone to achieve high precision.

What Is RTK Surveying?

RTK stands for Real Time Kinematic, a surveying technique that uses satellite positioning (GNSS) to obtain centimeter-level positioning accuracy in real time. While conventional GPS positioning accuracy is on the order of meters, RTK receives GNSS satellite signals simultaneously at both a dedicated reference station (base) and a mobile unit (rover), and reduces errors to a few centimeters or less by sequentially transmitting and correcting error information obtained at the fixed side to the mobile side. In Japan, network-type RTK that uses the Geospatial Information Authority’s Continuously Operating Reference Station network and the Quasi-Zenith Satellite System (Michibiki) CLAS augmentation signal is widespread, allowing high-precision positioning nationwide without having to set up your own base station.

By integrating this RTK surveying technology into mobile devices such as smartphones, it has become possible to obtain accurate coordinates on-site immediately. Previously, expensive dedicated GNSS surveying equipment was required, but by combining small high-precision GNSS receivers with smartphones or tablets, the benefits of RTK can now be enjoyed cheaply and easily. In particular, the concept of low-cost RTK (LRTK) has emerged in recent years, allowing smartphones to function as pocket-sized surveying instruments without carrying dedicated equipment. RTK can provide approximately horizontal 1-2 cm (0.4-0.8 in) and vertical 3-5 cm (1.2-2.0 in) accuracy, which is sufficient for general civil engineering as-built verification (areas requiring millimeter-level strict control (0.04 in level) are often supplemented with optical surveying instruments at key locations).

Simple Surveying Expanded by Smartphone × RTK

Combining smartphones with RTK makes surveying and as-built management on site accessible to anyone. The main advantages of smartphone + RTK are roughly twofold.

• Fewer personnel and shorter time to completion: Without specialized surveying equipment or skilled surveyors, one person can complete surveying work with only a smartphone and a small RTK receiver. For example, tasks that previously required two people (one holding a staff while the other measured) can be performed by one person with an RTK-compatible smartphone. There is no need to carry heavy tripods or levels; only pocket-sized equipment is required, improving mobility. In some cases, equipment operators can dismount and perform surveys themselves, and multi-skilled workers can improve personnel allocation efficiency.

• High-precision measurement data usable immediately: A major advantage is that photos and point cloud data acquired by the smartphone can be tagged on-site with centimeter-level position coordinates (half-inch accuracy). Point clouds captured in 3D can be recorded aligned to the design coordinate system from the start, without the need for post-processing to align to control points. The point cloud acquired by the scanner becomes direct evidence for as-built management and can be used immediately for design comparisons and quantity calculations. Traditionally, using high-precision point clouds required cumbersome post-processing, but an RTK-enabled smartphone provides measurement values that can be used on digital drawings the moment they are measured. With smartphones functioning as practical surveying instruments, the hurdle for as-built management is lowered and both speed and accuracy improve dramatically.

What Is Simple Surveying with LRTK?

A representative service that fuses smartphones, RTK, and point cloud measurement is LRTK. LRTK is a high-precision surveying app for iPhone that, when a dedicated small GNSS receiver is attached to the smartphone, enables all necessary measurements for as-built management with just an iPhone. It provides the following main features.

• Centimeter-class RTK positioning: It enables surprisingly precise positioning for a smartphone. Coordinates of various structures can be obtained in real time, and tasks such as leveling, stakeout height checks, and as-built height measurements can be easily performed by one person. Reference setting work that previously required multiple people can be completed by a single site worker with LRTK.

• 3D point cloud scanning: Utilizing the iPhone’s LiDAR sensor and camera, the site can be recorded on the spot as 3D point cloud data. High-density point clouds allow comprehensive visualization of completed structures, preventing oversights. Acquired point clouds are automatically tagged with position coordinates and saved, enabling later comparisons with design data and use for volume and quantity calculations.

• AR-based as-built inspection: An augmented reality (AR) feature overlays design 3D models or drawing information onto the actual site view. By projecting the finished 3D model onto the smartphone screen and comparing it with the structure under construction, deviations in the as-built can be intuitively understood. Position alignment is automatically performed using RTK high-precision coordinates, so the model will not drift. This is useful for explaining as-built status to clients and for on-site inspection attendance.

• Coordinate navigation (stakeout guidance): When placing stakes or structures at coordinates specified in design drawings, the smartphone screen and voice guidance can navigate you to the target coordinates. This allows stakeout and installation to be performed accurately by a single person, greatly improving the efficiency of stakeout operations. Tasks that were difficult to do alone, such as stake driving and setting out locations, become easy with LRTK.

• Automatic report generation: As-built management also requires preparing and organizing various documents, but with LRTK you can automatically generate reports with one button based on measurement results. Inspection records and as-built dimension management drawings, which were traditionally compiled manually, can be completed on the spot. Measured position data, notes, and photos are automatically formatted and output as PDF reports, freeing you from overtime spent on report preparation.

• Cloud sharing: Measurement data can be uploaded to the cloud and shared with the team and the client. Coordinates, point clouds, and photos acquired on site can be checked from office PCs in real time, allowing immediate information sharing with remote supervisors and owners. This enables remote supervision and quality checks without traveling to the site. Visualizing remote sites with data speeds up instructions and decision-making and reduces time loss in construction management.

Effects of Smart Surveying on the Field

By utilizing smartphone + RTK + 3D technologies as described above, significant benefits can be obtained in various aspects of construction management. The main expected effects of introducing smart surveying are summarized below.

• Significant reduction in work time: Because 3D point cloud scanning can capture wide areas of as-built at once, measurement tasks that used to take hours can sometimes be completed in minutes. Automatic report generation also dramatically reduces the time required to create reports and drawings. For example, as-built drawings that used to take half a day can now be completed instantly by scanning on site and pressing a button. Time spent on surveying and document preparation can be reallocated to other important tasks.

• Addressing labor shortages and labor saving: In today’s environment where fewer personnel are expected, as-built measurement that can be completed with a single smartphone is an effective measure to address labor shortages. Surveying tasks that previously required two or more people can be done by one person, improving personnel deployment efficiency. Because the system can be handled without highly specialized skills, site staff themselves can take on surveying duties in more situations. Multi-skilled work is promoted, enabling labor saving and productivity improvements across the team.

• Improved quality assurance and higher inspection pass rates: Point cloud data enables comprehensive measurement of construction areas, reducing the risk of overlooking out-of-spec parts. By checking progressively during construction, corrections can be made before final inspection points are raised. As a result, first-time inspection pass rates can improve and rework can be reduced. A wealth of digital data also facilitates smoother explanations to clients and increases credibility. You will no longer be hurried to provide additional materials requested by inspectors and can confidently attend inspections with presentable site documentation.

• Enhanced safety: Non-contact point cloud scanning and cloud-based remote status checks contribute to safety. They reduce the need for direct surveying work in hazardous locations such as heights and slopes, lowering the risk to workers. For example, even for tall structures, their shapes can be captured by LiDAR scanning from the ground rather than climbing. Shortening on-site work time also reduces risks such as heatstroke in hot weather and accidents during night work. In safety-first construction management, DX technologies are powerful allies.

• Smooth communication with clients and stakeholders: Intuitive visualization via AR and cloud data sharing smooths communication with clients and other departments. Previously, explaining the finished form required drawings and photos, but showing a 3D model overlaid on the real scene makes the situation immediately clear. For example, when reporting as-built for a revetment project, overlaying the design BIM model onto the actual view via a tablet helps the client easily imagine the as-built situation. Sharing the same data in meetings reduces rework and disputes caused by misunderstandings.

As described, introducing smartphone-based smart surveying and 3D as-built management yields many benefits. “More accurate, faster, safer, and more labor-saving” construction management can be achieved, reducing the burden on site personnel. Major construction companies have already started full-scale adoption of 3D as-built management, preparing internal manuals and training technicians. In one field demonstration, verification using a terrestrial laser scanner and design BIM data succeeded in dramatically reducing rework and streamlining inspection procedures. Some municipalities also provide subsidies to support ICT adoption, making it easier to try advanced technologies on site. Now is an excellent time to step into as-built management DX. As DX accelerates across the industry, it is important for those responsible for sites to get hands-on with digital technologies early.

Conclusion: Accelerate On-Site DX with Smart Surveying

With new technologies such as 3D surveying and RTK, surveying tasks on construction sites, including as-built management, are poised for major change. Smart surveying, which resolves previous inefficiencies and human errors while improving quality and safety and raising productivity, will become the new normal on future sites. For example, with LRTK, simplified surveying with centimeter-level accuracy (half-inch accuracy) can be performed with just a smartphone without complicated settings or specialized knowledge. Harness the latest technologies and start “3D as-built management DX” on your site from tomorrow. You will surely be surprised by the results. Experience the future of construction management on site. For more information, please also visit the [LRTK official site](https://www.lefixea.com/).

FAQ

Q. What is 3D surveying? A. A surveying method that acquires three-dimensional position coordinate data, including elevation, which cannot be obtained from traditional planar surveying. Using laser scanners or drone photogrammetry, terrain and structures are recorded as a large number of points (point clouds) to generate three-dimensional shape data. This enables digital grasp of terrain undulations and detailed structural shapes, and is utilized for as-built management and design review.

Q. How does RTK work? A. RTK is a technology that corrects satellite positioning (GNSS) errors in real time to measure positions with centimeter-level accuracy. Error information measured at a reference station is sent to the rover to correct GPS measurements, enabling high-precision positioning. In simple terms, special receivers and communications correct GPS deviations so that the exact current position (coordinates) can be known instantly.

Q. Can surveying really be done with a smartphone? A. Yes. By attaching a dedicated high-precision GNSS receiver to a smartphone and using an app, the smartphone can serve the role of a surveying instrument. Recent smartphones have improved sensor performance, and systems like LRTK enable point measurements with accuracy comparable to conventional surveying instruments. The operation is designed so that even those without specialized training can obtain surveying results by following guidance.

Q. Are special qualifications or knowledge required? A. Operating the smartphone surveying system itself is intuitive and simple, so advanced specialist qualifications are not required for basic use. Most site personnel can become proficient with a short training session. However, to correctly evaluate surveying results and reflect them in construction, basic knowledge of surveying and understanding of as-built management procedures are desirable. Also, tasks legally designated as requiring a licensed surveyor (such as certain public surveys) are subject to separate regulations, so be aware of those requirements.

Q. What if GNSS reception is not available? A. In places where the sky view is obstructed, such as urban canyons or tunnels, GNSS surveying including RTK can be difficult. In such cases, traditional instruments such as total stations, terrestrial laser scanners, or PPK (post-processing kinematic) methods for improving accuracy by post-processing are effective alternatives. It is important to select the optimal measurement method according to site conditions and, if necessary, combine multiple technologies.

Q. How can I adopt LRTK? A. LRTK consists of a dedicated GNSS receiver and a smartphone app. If you are considering adoption, contact LRTK via the inquiry form on the official site to request detailed materials or arrange a demo. You will be guided on required equipment and usage plans, and post-adoption support is provided. First, review product information and case studies on the official site to imagine how it can be used on your site.