Cloud-Connected × AR As-Built Inspection: A New Inspection Workflow Linking Field and Office

Table of Contents

• Introduction

• What is an as-built inspection? Traditional methods and challenges

• The new form of as-built inspection opened up by AR technology

• Innovative field–office workflow through cloud connectivity

• Main benefits of AR × cloud as-built inspection

• Conclusion: Outlook for simplified surveying with LRTK

• FAQ

Introduction

In recent years, digitization of construction management has accelerated through ICT adoption and DX promotion in the construction industry. However, on site many surveying and as-built inspection tasks still require significant time and effort, and challenges such as labor shortages and an aging workforce of technicians are becoming serious. With the "2024 problem" (application of overtime work regulations to the construction industry) looming, the need to advance site work efficiently with limited personnel is becoming even more pressing. Against this backdrop, establishing a new inspection workflow that seamlessly links the field and the office is required.

At the center of attention is the innovation of as-built inspection using cloud connectivity and AR (augmented reality) technology. In particular, by combining smartphones or tablets with high-precision GNSS using RTK positioning (real-time kinematic), there is potential to dramatically improve the efficiency of surveying and inspection work that has traditionally relied on experience and manpower through digital technology. Combining RTK's centimeter-level positioning accuracy (half-inch accuracy) with AR visualization of site information can turn palm-sized devices into "all-purpose survey instruments," enabling even non-experts to easily perform as-built measurements, stakeout, and verification of design data.

This article explains what AR as-built inspection is, its concrete benefits, and the new field–office workflow enabled by cloud connectivity. While reviewing the challenges of traditional methods, we will look at how introducing AR technology changes on-site inspections. Finally, we touch on the latest solution for simplified surveying using LRTK and offer hints for future construction management work.

What is an as-built inspection? Traditional methods and challenges

First, an as-built inspection is a check to confirm that the completed structures and terrain after construction match the design shape and dimensions. It measures the as-built condition (the finished shape) after construction—such as road width, slope of embankments, and volume of fill or excavation—and checks whether they conform to quality standards. As-built inspection is an important process that also serves as a deliverable to the client, and accurate measurement and recording are required.

In traditional as-built inspections, it has been common to measure elevations and positions point by point with surveying instruments such as total stations and levels, then calculate errors relative to design values on drawings. In recent years, there has also been increased use of photogrammetry and laser scanners to acquire 3D point cloud data and evaluate as-built conditions. However, these methods still have several challenges.

• Time-consuming and labor-intensive: Manually measuring many points one by one or processing data after drone aerial photography can take a long time to complete the inspection. For example, even for small earthworks, photogrammetry can take half a day from flight planning to point cloud generation and drawing.

• Requires specialized knowledge and personnel: Operating surveying equipment and processing data requires experienced technicians, which can be difficult to secure at sites with labor shortages. Drone operation may require qualifications or permits, posing high barriers for small sites.

• Division between field and office: Traditionally, data measured on site are taken back to the office for organization and drawing before results are shared. This makes it difficult to share information and correct issues with stakeholders immediately when problems are found on site, often causing rework.

• Communication gaps: Survey results are reported as numbers or on drawings, making it hard to convey the on-site situation intuitively. Aligning understanding with clients and other departments can take time, and in some cases discrepancies in understanding lead to rework.

Thus, while as-built inspection is indispensable for quality control, traditional methods face challenges in efficiency and information sharing. This is where the new approach using AR technology and cloud connectivity, described next, comes in.

The new form of as-built inspection opened up by AR technology

By utilizing AR (augmented reality) technology, on-site work for as-built inspection is undergoing significant changes. AR is a technology that overlays digital information on the real-world image seen through a camera. Using this, you can virtually display a 3D model of the design or reference lines on the actual structure or terrain at the site, allowing intuitive recognition of differences and information that are invisible to the naked eye.

For example, imagine standing at an embankment construction site with a tablet. If you AR-display a prepared design model or a reference line such as a finished elevation of ○ m (○ ft) over the embankment as seen through the device camera, you can instantly confirm whether the current terrain has the design slope. If a part is higher than the design, it will appear to protrude from the virtual model, enabling immediate action such as trimming excess fill. Tasks that previously required point-by-point numerical comparison or returning to the office for drawing checks can now be done intuitively on site.

Recently, some smartphones and tablets have been equipped with LiDAR sensors. By combining these with high-precision positioning information, you can walk around the site and 3D-scan the surrounding terrain and structures, acquiring as-built point cloud data on the spot. For instance, in one approximately 150㎡ case, by walking the surface with an RTK-capable tablet and LiDAR measurement, detailed point clouds were obtained in about 15 minutes. Where traditional drone photogrammetry and post-processing took more than half a day, smartphone AR surveying completed the as-built measurement in just a few dozen minutes. The acquired point cloud is tagged with high-precision absolute coordinates on site, eliminating the need for office-based georeferencing.

The advantages of AR-based as-built inspection are not only speed. Making inspection visually understandable enables everyone from site staff to clients to more easily share the same information. For example, if you display a 3D model of the completed appearance at the site with a tablet, the "completed image" that was difficult to convey with paper drawings can be shared instantly during a walkthrough with the client or local residents. Since all stakeholders can view the same virtual model and align their understanding, explanation time is reduced and the risk of rework due to mismatched recognition is lowered. There are reports that AR adoption has "almost eliminated misunderstandings in conveying design intent" and that "defects are discovered on site and corrected immediately," demonstrating effectiveness in consensus-building and quality assurance.

Moreover, AR contributes to safety improvement. For example, tasks such as stakeout on steep slopes that previously involved risk can be safely checked without assistants by displaying virtual stake markers in AR. Displaying the location of buried pipes in AR allows you to understand pipe routes as if seeing through the ground, helping prevent accidents from accidental excavation. In this way, AR technology promotes "visualization of the site" across construction management, creating new value in efficiency, accuracy, and safety.

Innovative field–office workflow through cloud connectivity

Alongside AR, cloud connectivity is a key factor in transforming as-built inspection workflows. By leveraging the cloud, measurement data and records obtained on site can be shared with the office instantly, allowing the entire team to handle geospatial information in real time. This connects the traditionally divided field and office seamlessly and enables a new workflow.

One concrete advantage of cloud connectivity is the immediacy of data sharing. For example, if you upload point cloud data of the as-built condition or high-precision geotagged photos acquired with a smartphone to the cloud on the spot, the office PC can view the data immediately. Coordinates measured on site are plotted on a web map, allowing remote offices to grasp progress in real time. This lets field personnel and office staff share information without time lag and determine within the same day "how far as-built verification has progressed today" and "whether there are any problematic measurement results."

Cloud delivery also facilitates remote attendance and inspections. If on-site staff live-stream the tablet camera view with AR overlays or share AR-composited photos uploaded to the cloud, clients and inspectors can check the on-site as-built condition while staying in the office. This makes it possible to carry out parts of the as-built inspection attendance remotely—reducing travel time and enabling faster inspections.

Two-way information linkage is another cloud-specific advantage. The latest design drawings and instructions prepared in the office can be sent instantly to field devices via the cloud and displayed in AR. On site, inspections and construction proceed based on the latest information, reducing rework due to drawing inconsistencies or communication errors. Conversely, as-built data collected on site are accumulated in the cloud, enabling automation and simplification of later documentation and as-built management chart creation. For example, cloud services could automatically analyze point clouds acquired on site and generate a heat-map style as-built management diagram to share with stakeholders.

Thus, cloud connectivity powers the rapid cycle of "acquire data on site → immediately share to cloud → office reviews and issues instructions → field acts," enabling all stakeholders to collaborate using the same up-to-date information and realizing a smooth inspection workflow with minimal mistakes or waste.

Main benefits of AR × cloud as-built inspection

The as-built inspection method combining AR technology and cloud connectivity offers many benefits compared to traditional approaches. The main effects are summarized below.

• Significant time savings and efficiency: Smartphone AR surveying dramatically reduces the time required for as-built measurement and earthwork volume calculations. There are examples where tasks that took half a day with drone photogrammetry were completed in less than 30 minutes, and the speed of inspection and reporting has improved dramatically. Because one person can survey a wide area efficiently, some sites report productivity gains so large it felt "as if the workforce had doubled."

• Reduced manpower and labor savings: AR enables more instances of single-person surveying and single-person inspection. Tasks that previously required multiple people for as-built verification or stakeout can be performed by one person following on-screen smartphone guidance, alleviating labor shortages. It also allows work in difficult terrain without assistants, contributing to safety.

• Improved accuracy and reliability: With RTK high-precision positioning, AR-displayed models and measured data are within an error range of a few centimeters (a few inches). Subtle deviations that could be overlooked by the naked eye or simple GPS can be detected, enabling strict comparison with design values. Because acquired data already include accurate coordinates, alignment errors in subsequent processes do not occur. When operated properly, AR as-built inspection can secure accuracy suitable for practical use.

• Real-time problem detection and correction: By continuously overlaying design data in AR during construction and inspection, nonconformities can be discovered and addressed on the spot. During inspection attendance, site staff can compare the design model and the constructed object on a tablet and correct defects immediately if found. By not carrying problems forward to later days, quality variability is reduced and rework is minimized.

• Improved information sharing and communication: AR provides visual information that is "understandable at a glance," making site conditions easier for anyone to comprehend regardless of technical expertise. Sharing that information via the cloud helps stakeholders with different roles—clients, site supervisors, and workers—develop a common understanding, smoothing consensus building. As a result, communication across the project is streamlined and losses from miscommunication decrease.

• Cost reduction: Outsourcing to specialized surveying companies can be reduced, and short inspection times lead to lower personnel costs and reduced daily expenses. Using smartphones and tablets can leverage existing devices and therefore keep initial investment costs low. Because it is possible to start without equipping expensive dedicated instruments, the investment return can be high even for small sites.

Thus, AR × cloud as-built inspection is a highly effective solution for shortening construction schedules and reducing labor while maintaining quality. For construction sites facing labor shortages and work-style reforms, it can be a powerful ally that achieves both efficiency and sophistication.

Conclusion: Outlook for simplified surveying with LRTK

As-built inspection that combines cloud connectivity and AR technology holds great potential as a new inspection workflow linking the field and the office. If digitization enables anyone to intuitively and accurately perform surveying and inspection, "simplified surveying" on site will advance and the previously routine wasted effort and waiting times will be reduced. Indeed, AR × RTK is opening up a new norm for surveying and as-built management.

One solution embodying this new norm is LRTK. LRTK is a smartphone surveying system in which a small RTK-GNSS receiver is attached to a smartphone and a dedicated app is used to perform positioning, point cloud measurement, stakeout, and AR display all with one device. It offers positioning accuracy comparable to specialized equipment while being simple to operate and designed so anyone on site can use it easily. Acquired data can be synced to the cloud with one tap, enabling immediate sharing and review without returning to the office. It is truly a powerful tool for putting into practice the cloud-connected × AR as-built inspection discussed in this article.

If simplified surveying with LRTK becomes widespread, the conventional assumptions that "surveying must be left to licensed surveyors" and "as-built management takes time" may change. A future in which each field staff member carries high-precision surveying capabilities in their pocket and proactively measures, inspects, and records is just ahead. Consider adopting the new inspection workflow enabled by cloud connectivity × AR and the simplified surveying approach proposed by LRTK to improve productivity and realize work-style reforms on your sites.

FAQ

Q1. What equipment and preparations are required to introduce AR as-built inspection? A. You can get started without special high-cost equipment or advanced knowledge. Basically, all you need is a smartphone or tablet capable of AR display and a GNSS receiver to acquire high-precision positioning information. For example, using a solution that combines a small RTK-GNSS receiver that attaches to a smartphone with a dedicated app (such as LRTK), you can perform intuitive AR as-built inspection simply by attaching the device and launching the app. Initial setup and operation are simple, and field personnel can quickly become proficient.

Q2. Can smartphone AR display really provide accurate measurement and position confirmation? A. Yes—if operated appropriately, it can provide high-precision measurement and positioning. Standalone smartphone GPS can have errors of several meters (several ft), but using RTK correction for GNSS positioning can reduce errors to the order of a few centimeters (a few inches). In practice, RTK-capable smartphone AR systems achieve positioning where the design location on drawings and the AR-displayed position on site almost coincide. Acquired point clouds and coordinate values are also high-precision, so they can be recorded with quality sufficient for official as-built management.

Q3. Can AR as-built inspection be used in locations where satellite reception is difficult or indoors? A. In environments where GNSS satellite signals are unstable—such as urban canyons or under dense trees—high-precision RTK positioning may be difficult. In such cases, workarounds include once aligning to control points in an open area and then performing short tasks using the smartphone’s internal sensors or camera markers to maintain position. However, in completely GNSS-denied indoor or underground spaces, precise AR positioning is currently challenging with existing technology. In those situations, you may need to rely on traditional methods such as total stations or await future technological advances. Note that LRTK supports Japan’s Quasi-Zenith Satellite System (QZSS) CLAS high-precision augmentation signals, which helps compensate positioning when satellite visibility is limited. Going forward, combining satellite positioning with other sensor technologies will enable more stable AR as-built inspection across broader environments.

Q4. Is there any benefit to introducing AR and cloud on small sites or short-term projects? A. Yes—in fact, small projects and short-term works with limited personnel can benefit greatly. For example, as-built measurements that were previously outsourced to external surveying firms can be completed quickly by a single in-house staff member using AR surveying. This reduces outsourcing costs and the overhead of scheduling. Even on short-term sites, daily progress checks and as-built inspections using AR and cloud allow quick situation assessment and recording as needed. Digital data can be handed over to subsequent processes immediately, enabling thorough construction management even for short schedules. AR technology contributes to efficiency and quality improvement regardless of project scale.

Q5. Is it possible to use dedicated AR devices such as smart glasses? A. There are cases using see-through AR glasses or helmet-mounted devices. However, dedicated AR glasses are generally very expensive and have practical issues such as narrow field of view and operational difficulty, making broad on-site adoption challenging. In contrast, using smartphones or tablets allows leveraging devices many people are already familiar with, and keeps introduction costs relatively low. Solutions designed around smartphone use, like LRTK, balance RTK GNSS positioning accuracy with the convenience of smartphone AR. It is practical to start with AR as-built inspection on a personal smartphone or tablet and consider other devices as needed.