Turn Your Smartphone into a High-Precision Surveying Instrument! As-Built Management DX Anyone Can Do

In the construction industry, one of the important processes in construction management is as-built management. As-built management is the management task of verifying that completed structures and construction elements have been finished in the shapes and dimensions specified by the design drawings, thereby ensuring quality. Until now, as-built management centered on manual work that required much manpower and time, and compiling measurement results into drawings and tables was also cumbersome. However, in recent years, new technologies that leverage smartphones and GNSS (Global Navigation Satellite System) have ushered in an era in which anyone can easily digitally transform (DX) as-built management. This article begins with an overview and the importance of as-built management, then provides a detailed explanation of the challenges of traditional methods, the mechanisms and benefits of high-precision surveying using smartphones + GNSS, the scope of smartphone surveying applications such as point cloud scanning and AR (augmented reality), actual implementation cases and effects, consistency with the Ministry of Land, Infrastructure, Transport and Tourism’s policies, the features and concrete use methods of a solution called LRTK, and finally the implementation steps and key points for adoption on site. It is a comprehensive collection of useful information for those searching for "as-built management construction management".

Overview of As-Built Management and Its Importance in Construction Management

First, we will outline why As-built management is important in construction management. As-built management refers to the process of verifying and recording whether completed structures and work areas conform in shape, dimensions, and quality to the design after construction. The construction contractor (the party awarded the contract) is required to measure dimensions in accordance with specified standards, compile the deviations from the design values into documents such as as-built management diagrams and tables, and submit them. This serves as proof of quality for the client and supervising authorities, and in public works it is required evidence during inspections.

By properly carrying out as-built management, you can detect early whether the constructed works deviate from the specifications and correct them as necessary. For example, in road construction, as-built management checks whether the subbase and pavement thicknesses are the design-specified thickness and whether the gradient of slopes falls within the prescribed range. As-built management, which is a key element of quality assurance and inspection response, if neglected can lead to significant rework or repairs later, adversely affecting the schedule and costs. Therefore, in construction management, as-built management is an indispensable and important process and can be regarded as the last line of defense in protecting on-site quality.

Challenges of Conventional Methods (manpower, time, accuracy, cost, drawing preparation effort, etc.)

However, traditional as-built management presented various challenges. In a typical procedure, surveying staff use tape measures, levels, and total stations (TS) to measure dimensions and elevations at various locations, and record those values by hand or in Excel. The following problems have been pointed out with this analog method.

• Workforce and time burden: In large-scale construction projects, the number of measurement points is also high, requiring teams of multiple people to spend long hours conducting surveys. For example, when measuring the height of a slope, surveyors had to go onto the slope and take measurements while directing each other, which not only involved danger but also resulted in inefficient work.

• Human error and accuracy issues: Because scale readings and numerical recording are done manually, there is always a risk of human errors such as misreading or miswriting. Omissions when transcribing handwritten notes or calculation mistakes can also lead to errors in as-built dimensions or missing records.

• Specialized equipment and cost: To perform high-precision measurements, expensive specialized equipment such as TS and high-performance GNSS surveying instruments were required. The cost of purchasing and maintaining equipment, and securing skilled operators who can operate them, were also challenges. In small- and medium-sized sites, there were cases where implementation was abandoned for cost reasons.

• Post-measurement processing burden: After measurements are completed, creating as-built management charts and reports back at the office is also a major task. Plotting measurement points on drawings and entering data into Excel for checking is time-consuming, and there was a time lag between measuring in the field and being able to confirm the final form. If construction defects were discovered during that interval, there was a risk that work would have already progressed and require rework.

In recent years, with the spread of ICT-based construction, new methods have emerged, such as conducting point-cloud surveys of sites using drone aerial photographs and 3D laser scanners and analyzing the as-built. This has made it possible to digitize areas that cannot be measured directly by people; however, challenges remain. In drone surveying, to achieve high accuracy it is necessary to install control points (known-coordinate points) in advance and georeference (coordinate alignment) the acquired photographic data in post-processing. Also, in laser scanner measurements, the equipment itself is very expensive, and data processing requires specialized software and a long time. With either method, it is difficult to grasp results in real time on site, and the process was that the as-built could only be confirmed after surveying, once it had been analyzed and drafted in the office.

As described above, conventional as-built management methods were labor- and time-intensive and carried a high risk of mistakes, and they were constrained by the inability to confirm results immediately on site. To resolve these issues, a new approach that enables easier, real-time understanding of as-built conditions was needed.

How High-Precision Surveying Technology Using Smartphones and GNSS Works (Including an Explanation of RTK)

That led to the emergence of high-precision surveying technology that combines smartphones and GNSS. The GPS built into typical smartphones has an error of several meters and, as-is, cannot meet the accuracy required for as-built management (cm level accuracy (half-inch accuracy)). However, by using an external high-precision GNSS receiver attached to the smartphone and employing a positioning method called RTK (Real-Time Kinematic), it has become possible to transform a smartphone into a cm level accuracy (half-inch accuracy) surveying instrument.

RTK-GNSS positioning is a technique that obtains high-precision positions by simultaneously receiving GNSS satellite signals at two points—the reference station (base station) and the mobile station (rover)—and comparing and correcting their data in real time. The reference station is a control point with known precise coordinates, and the mobile station is the side being positioned (in this case, the smartphone). By exchanging observation data between the two via communications and cancelling error sources contained in the satellite signals (such as atmospheric effects and clock errors), it achieves high-precision positioning with errors of a few centimeters (a few in) or less. Traditionally, dedicated survey GNSS equipment and radio communication devices were required, but today internet-based correction information distribution services (for example: network RTK services) are well established, making RTK positioning easily usable even with a smartphone + GNSS receiver.

By using a GNSS receiver device that attaches to a smartphone (for example, products called LRTK), handheld devices like iPhones and iPads can serve as rovers for high-precision positioning as they are. Reference stations can use public control points, temporary base stations, or virtual reference points provided via cellular networks, so there is no need to install expensive equipment at each site. This system has made it possible to create an environment where anyone can instantly perform centimeter-level surveying. As a result, as-built measurements that previously relied on specialist technicians can now be handled by ordinary workers, greatly contributing to on-site reduced staffing and labor. Furthermore, if measurement results can be immediately compared with design values on the smartphone screen on the spot, it prevents situations where defects are not noticed until returning to the office to create drawings. With the smartphone becoming a high-precision surveying instrument, the as-built management process itself becomes real-time and more efficient, dramatically improving the on-site quality confirmation cycle.

The scope of smartphone surveying applications, such as point cloud scanning, AR visualization, and cloud integration

Surveying with a smartphone combined with high-precision GNSS does more than simply measure point coordinates. Smartphones are equipped with cameras and LiDAR (light detection and ranging) sensors, and by combining these it becomes possible to utilize a wide range of applications such as 3D point cloud scanning, AR visualization, and cloud integration. In the field of as-built management, let’s look at one example of the new solutions smartphone surveying can provide.

• High-precision 3D point cloud scanning: By scanning a site with a smartphone camera or LiDAR, you can easily obtain three-dimensional point cloud data of terrain and structures. Traditional standalone smartphone LiDAR scans suffered from ambiguous position coordinates and data distortion when moving around. However, smartphone surveying combined with high-precision GNSS can give every acquired point cloud a global coordinate (geodetic coordinate). Because the system corrects its position in real time while scanning, consistency between point clouds is maintained even during movement, producing distortion-free, accurate 3D models. This enables anyone to acquire georeferenced point clouds without specialized equipment and to directly measure arbitrary distances between two points, areas, volumes, and more on site. For example, if you want to know the volume of fill at an earthwork site, you can simply take your smartphone out of your pocket and scan the ground surface to instantly calculate the fill volume. There is no need to carry heavy laser scanners or a laptop, making it revolutionary for easily collecting detailed as-built data.

• Overlaying design data with AR: Smartphones that can pinpoint position precisely with GNSS become powerful on-site inspection tools when combined with AR technology. For example, if you load drawings or 3D design model data onto the smartphone, you can view the design model overlaid on the current scenery using AR display to overlay the design model. As an application for as-built management, one use case is to create on the cloud a heatmap that compares measured point cloud data with design data and color-codes the differences, transfer it to the smartphone, and display it on site via AR. By simply holding the smartphone over the ground, information such as "where fill is lacking" and "which spots have finished elevations higher than the standard" will jump out intuitively by color. Traditionally, even marking defective as-built areas required finding the position on drawings and staking it out on site… but with centimeter-level accuracy (half-inch accuracy) AR display you can immediately identify problem areas on site and start rework right away. AR visualization also helps in other ways—for example, overlaying a 3D model of the completed structure onto the pre-construction local landscape so the client and project stakeholders can share the finished image. By incorporating AR into daily construction management tasks, on-site communication and verification work will be dramatically streamlined and enhanced.

• Cloud integration and data sharing: As-built data acquired with a smartphone can be uploaded to the cloud instantly via mobile communications. On the cloud platform, you can, from a browser, plot surveyed coordinate points on a map and list them, or display acquired point cloud data in a 3D viewer for analysis. Without using specialized CAD software or point-cloud processing software, as long as you have an internet connection you can check detailed as-built conditions of the site from the office. Furthermore, on the cloud you can overlay design data (for example, a pre-construction design model) with current point clouds and automatically calculate the quantity differences. This can greatly reduce the time required to aggregate daily fill and excavation volumes, and enable integrated digitalization of as-built management and construction quantity management (dekidaka = the amount of work executed). Also, by sharing data between the field and the office, or with the client, via the cloud, you can streamline inspection and reporting procedures. You can also reduce the hassle of mailing paper forms or handing over data on USB, and seamlessly support electronic delivery.

In this way, the scope of smartphone surveying is not limited to measuring points but extends to the acquisition of 3D measurement data, advanced visualization, and the sharing of information both within and outside the team. By incorporating these technologies into as-built management, site personnel will be able to perform quality checks in an intuitive and accurate way like never before.

Implementation case studies, operational workflow, costs, benefits, and accuracy results

So, what actually changes on-site when smartphone surveying is applied to as-built management? Let’s look at the implementation benefits and accuracy results while tracing the operational workflow.

◎ New workflow for as-built measurement: By introducing a smartphone plus a high-precision GNSS device, the entire sequence of as-built management tasks can be completed on site. A typical workflow is as follows.

• Acquiring as-built data: First, use a smartphone to measure the as-built condition at the construction site. In addition to single-point surveys at individual locations, you can simply walk with the smartphone to scan an entire area and capture surface geometry. For example, in slope work you can walk from the top to the bottom of the finished slope to scan and obtain comprehensive 3D data.

• Comparison with design data: Next, perform comparisons with the design values on site. The smartphone app can automatically calculate errors by comparing each measurement point with the design dimensions, or create heat maps by overlaying point cloud data uploaded to the cloud onto the design 3D model—enabling real-time verification. This allows you to identify locations deviating from standards immediately after measurement.

• Record storage: Measurement results are automatically recorded digitally. Because date and time, the measurer, the coordinates of measurement positions, errors, photo notes, and so on are linked and saved to the cloud, there is no need to later re-enter handwritten field notes from paper notebooks into Excel. Measured data is organized on cloud-based maps and in tabular form so authorized stakeholders can view it immediately.

• Report creation and submission: Finally, compile the as-built management results into reports or electronic delivery data. Smartphone surveying systems also offer a feature to output with one click the prescribed as-built management charts and inspection files for 3D point clouds from the acquired data. This dramatically shortens the time from measurement to report submission and reduces the administrative burden on site personnel.

◎ Effects observed from case studies: In actual job sites, many benefits have been reported from the digital transformation (DX) of as-built management using smartphones. At one large-scale earthwork site, the slope as-built surveying and chart creation that used to take a two-person team half a day was completed, after introducing smartphone surveying, by one person in less than an hour. Because the entire slope was measured by point cloud scanning, nothing was overlooked, and defective areas were immediately identified and reworked the same day. As a result, deficiencies that would likely not have been noticed before inspection were corrected early, keeping later rework to zero. In another paving project, the surface immediately after paving was scanned with a smartphone to check flatness, and by using color-coded maps to identify unevenness, even slight height differences were repaired without omission. This led to an improvement in as-built evaluation scores (higher pass rates in inspections).

◎ High accuracy and cost benefits: The positioning accuracy achieved by smartphones plus GNSS, as has already been demonstrated, falls within errors of a few centimeters or less horizontally (a few in or less) and at most a few centimeters vertically (a few in). For example, by using the averaging function of a dedicated app for static positioning, a very high accuracy with a standard deviation of less than 1 cm (less than 0.4 in) in planar position can be achieved. This level of accuracy fully meets typical public-works as-built control standards and rivals conventional total-station surveys and high-end GNSS equipment. Nevertheless, the introduction cost is substantially lower than that of traditional equipment. Centimeter-level GNSS receivers (cm level accuracy (half-inch accuracy)) once commonly cost several million yen per unit, but smartphone-compatible compact receivers can be purchased at a one order of magnitude lower price (around several hundred thousand yen). In addition, subscription (monthly fee) plans that include cloud services are sometimes available, offering the flexibility to begin implementation without large upfront investments. Due to this high cost-effectiveness, operations such as providing every field worker with one smartphone surveying device are becoming realistic. In practice, keeping the device in a pocket at all times so measurements can be taken immediately when needed has eliminated waiting time for surveying equipment and greatly improved productivity, according to reports. Combined with the ease of use that allows anyone to operate it after a short training, smartphone as-built management is evaluated as a solution with a short investment payback period and easy to introduce.

Consistency with the Ministry of Land, Infrastructure, Transport and Tourism's Policies and Electronic Delivery Requirements

The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) is also actively promoting the introduction of ICT technologies and digital transformation in the field of construction management. The area of as-built management is no exception, and in recent years procedures and guidelines related to as-built management using 3D measurement technology have been developed. For example, standards such as "Guidelines for As-built Management Using TS (Earthwork Edition)" and "Guidelines for As-built Management Using RTK-GNSS (Earthwork Edition)" have been established, and the standardization of ICT-based as-built management is being promoted, mainly for large-scale earthworks. As-built measurement using smartphone + GNSS can be said to be an innovative practical example of this RTK-GNSS as-built management method. Because measurements and recordings can be performed in a manner that meets the required accuracy and procedures, it is possible to produce deliverables that conform to the MLIT's prescribed procedures.

In addition, smartphone surveying is extremely effective in terms of responding to electronic delivery (submission of digital deliverables). Traditionally, as-built management deliverables have typically been paper drawings and charts or Excel sheets prepared in accordance with electronic delivery procedures. However, in recent years some contracting authorities have increasingly accepted the submission of digital measurement data itself, such as point cloud data and 3D models (digital measurement data itself). Point cloud data and measured coordinates acquired with a smartphone can be recorded in formats that conform to Japan’s surveying reference systems (the plane rectangular coordinate system and the vertical datum), making them directly usable as electronic deliverables. For example, the draft As-Built Management Guidelines (出来形管理要領 (draft)) covers multiple 3D measurement methods such as terrestrial laser scanning and drone aerial photography, and RTK-GNSS surveying is also listed as an important option. Point cloud data obtained with smartphone GNSS can be submitted as point clouds with absolute coordinates if accuracy verification using control points is performed, and the contracting authority can use them to determine pass/fail of the as-built compliance. This represents a step toward replacing traditional paper drawings with the direct use of digital data in inspections, and could be regarded as the ultimate form of DX in as-built management.

Furthermore, when introducing such new technologies at worksites, the Ministry of Land, Infrastructure, Transport and Tourism and each Regional Development Bureau sometimes offer support measures and call for model construction projects as part of initiatives such as i-Construction and CIM (Construction Information Modeling). By proactively utilizing new as-built management technologies, companies can be recognized as examples of advanced initiatives, which can lead to improved competitiveness. In other words, smartphone-based DX for as-built management aligns with the direction the government is aiming for and is a method that could become standard in the future.

LRTK Features and Specific Applications for As-Built Management DX

One of the solutions to turn a smartphone into a high-precision surveying instrument is the aforementioned LRTK (Eruarutīkē). LRTK is a system developed by Reflexia, a startup originating from Tokyo Institute of Technology, consisting of a small RTK-GNSS receiver device and a dedicated app. Designed to be attached to an iPhone and used, it is lightweight and compact at approximately 165 g, yet transforms a smartphone into a versatile surveying instrument with cm-level accuracy (half-inch accuracy). Let's take a concrete look at its features and how it can be utilized in DX for as-built management.

• Easy to attach and usable by anyone: LRTK includes a smartphone case–style attachment and a one-touch detachable antenna module, making on-site setup extremely simple. The equipment configuration is also simple: just the smartphone itself and the LRTK receiver, and, in some cases, a monopod for height measurement (optional). The app’s operation is intuitive, and no complicated settings are required to start positioning. It is designed so that even those without surveying expertise can learn the basic operations with a short training. By enabling everyone on site—from junior staff to veterans—to survey with their own smartphones, it contributes to promoting DX across the entire organization.

• Versatile measurement and recording functions: The LRTK app integrates a variety of features useful for as-built management. Single-point coordinate measurements can be performed with a single button press, and the measured latitude, longitude, and elevation are automatically converted to Japan Plane Rectangular Coordinates and geoid height and recorded along with the date/time and surveyor information. You can take and attach photos for each survey point and leave notes, allowing the site’s as-built condition to be recorded like an electronic field notebook. In addition, using continuous measurement mode you can automatically acquire points at regular intervals while walking or collect surface scan data. The acquired point cloud data can not only be viewed within the app but also uploaded to the LRTK cloud with one tap. On the cloud, measured points are plotted on a map and listed, and advanced visualizations—such as overlaying 3D data with photos in a point cloud viewer—are also possible. For example, scanning a bridge with point clouds and photographing any concerning cracks for record can all be completed on a single platform with LRTK. These functions seamlessly connect the steps of measuring, recording, and verifying required for as-built management, eliminating the hassle of switching between paper drawings, a camera, and a notebook.

• Real-time quality checks and navigation: With LRTK, performing real-time quality checks on-site is also easy. For example, if you want to know how the current height compares to the specified design elevation, you can set a reference elevation in the LRTK app and it will instantly display the difference from the measured elevation on the spot. You can also import heat map data generated in the cloud to your smartphone and, while displaying it in AR on-site, search for nonconforming areas. Furthermore, LRTK has a coordinate navigation feature: if you specify the coordinates of the target point in the cloud ahead of time, your smartphone will guide you with direction and distance to it. This allows you to find the target position with cm level accuracy (half-inch accuracy) even when you only know roughly where it should be on the drawings but not the actual location. Another advantage unique to LRTK is that it includes functions that can be widely applied to surveying and inspection tasks beyond as-built management, such as laying out the positions of buried utilities and locating known points on existing structures.

As described above, LRTK is a solution that provides, via the familiar tool of smartphones, concrete measures for as-built management DX. Because it can consistently handle everything from high-precision positioning to point cloud measurement, AR-based checks, and data sharing, introducing it will dramatically streamline on-site quality control workflows. LRTK, which achieves both improved accuracy in quality assurance and reduced operational burden, can truly be said to embody the next generation of as-built management tools.

Steps for Implementation and Key Points for On-site Adoption

Finally, we explain the implementation steps and key points for ensuring adoption of smartphone-based construction quality management DX on site. Introducing new technologies requires planning and ingenuity, but by following the steps below you can smoothly integrate them into the field.

• Clarify the purpose and obtain internal agreement: First, clarify why you are introducing smartphone surveying. Share within the company the effects you want to achieve—such as "improving as-built management efficiency," "enhancing safety," and "addressing labor shortages"—and obtain agreement from senior management and site supervisors. With understanding and support from upper management, deployment to the field will proceed more smoothly.

• Prepare necessary equipment and services: When introducing the system, select and procure the smartphones, GNSS receivers, compatible applications, and RTK correction information services (if using a network). If you plan to use existing iPhone/iPad devices on hand, check that they are supported and procure additional devices if needed. If you will use cloud services, complete account registrations and service agreements in advance.

• Initial setup and trial operation: Once equipment is assembled, conduct field trials to verify operation. Check connection to control points, coordinate system settings, and whether positioning is performed correctly. If possible, measure known points (points with known coordinates) to verify that errors are within the expected range. Start with a small area or lower-priority sections and prepare for full-scale operation.

• Training for site personnel: Provide education and training to site staff and workers on how to operate smartphone surveying and handle data. For intuitive systems like LRTK, a half-day hands-on training following the operation manual should be sufficient for users to become proficient. Have not only new and younger employees but also veteran staff participate to deepen organizational understanding of digital tools. It's important to resolve questions and concerns and give everyone confidence that they can use the tools.

• Full-scale implementation and follow-up: After sufficient trials and training, introduce smartphone-based as-built management in actual construction projects. In the initial phase, it can be beneficial to run it in parallel with traditional methods and familiarize the field by comparing results from both. Reduce resistance by having a transition period—gradually eliminate paper records and switch to digital records. Also, follow up regularly on progress and issues for some time after introduction. Administrators should check the data accumulated in the cloud, verify correct field usage, consider potential improvements, and provide additional guidance or review system settings as needed.

Key points for successful adoption: To embed new technology on-site, there are several key points. First, involving key on-site personnel is essential. Have proactive staff and younger employees who are positive about digital devices take leadership roles, and create a system where they actively teach other members how to use them—this makes it easier for the entire site to improve its proficiency. Also, sharing success stories is important. Share internally episodes from smartphone-based as-built management such as "work became so much easier," "mistakes decreased," and "we were praised during inspections" to boost motivation. When the benefits experienced on-site are communicated, others will begin to engage voluntarily.

Furthermore, in the initial implementation, aligning with existing operations is also a key point. To reflect digitally acquired data in the final deliverable drawings and forms, it is necessary to consider compatibility with the formats previously used. Because the provider of the LRTK prepares form templates that follow the Ministry of Land, Infrastructure, Transport and Tourism guidelines, utilizing them will help facilitate a smooth transition to electronic deliverables. It is also important to actively show the data obtained by the new methods to clients and supervisory staff to gain understanding and trust. If inspectors are unfamiliar with digital deliverables, it can be effective to also present printed comparison tables and other materials, gradually guiding them to verification using electronic data.

Finally, set up a continuous support system. Collect software and device update information on an ongoing basis, apply updates on-site as needed, and designate internal support staff or manufacturer help desks who can be contacted when problems occur — having operational support like this is reassuring. Fortunately, systems that use smartphones and small devices are easy to handle and seldom encounter problems, and if a device does fail it can be quickly replaced and reconfigured. While leveraging these characteristics, incorporate feedback from the field to improve operations and cultivate them into DX tools that truly take root on-site.

This has provided a detailed introduction to as-built management DX using smartphones, covering everything from the overview to implementation. A smartphone can become a high-precision surveying instrument — a change that may seem revolutionary at first, but once you try it on site you'll surely feel that "because it's safe and convenient, you can't give it up." As a trump card for achieving both productivity improvements and quality assurance on construction sites, please experience the digitization of as-built management with smartphones + GNSS at least once. The adoption of new technology will be the first step toward opening up the future of the job site.