A Must-See for Surveying Engineers! Introducing Point-Cloud As-Built Management to Make Inspection Document Preparation Three Times Faster!

In recent years, the introduction of point cloud data into as-built management has been attracting attention at construction sites. The work of creating as-built drawings and forms, which had been primarily manual until now, has been greatly streamlined by point cloud technology, and there are cases where inspection document preparation proceeds at more than three times the speed of conventional methods. For surveyors and construction management engineers, the DX (digital transformation) of as-built management is an unavoidable trend. This article explains how as-built management methods using point cloud data speed up and reduce labor in the preparation of inspection documents, comparing them with conventional methods and discussing specific functions (3D heat maps, cross-section extraction, automatic evaluation, automatic report generation, cloud sharing, etc.). Finally, we also introduce the current situation in which anyone can easily implement point-cloud-based as-built management thanks to the advent of easy high-precision surveying (LRTK surveying) that combines smartphones and compact GNSS.

Challenges of Conventional As-Built Management and Inspection Document Preparation

First, let's briefly review what as-built management is. As-built management is a construction management process that verifies and records whether the shapes and dimensions of constructed structures and ground are finished in accordance with the design drawings. It is essential for ensuring quality and is a critical task that underpins passing construction inspections and handover, but various issues have been pointed out with traditional as-built management methods.

• High labor and time burden: Manual surveying using tape measures, leveling staffs, total stations, etc., required enormous time and manpower to measure wide sites and the details of complex structures. Point-by-point measurements were inefficient, and combined with recent labor shortages they became a burden for site personnel.

• Limited measurement points and risk of oversight: Manual measurements only provided dimensional data for each point, making it difficult to grasp the overall slope of a surface or local irregularities. Differences from the design between measurement points could go unnoticed, posing the risk that, during inspection, someone might point out "some shapes differ from the drawings."

• Safety issues: Measuring in areas that are difficult for people to access—slopes at height, the undersides of bridges, narrow tunnels—was challenging. Because attempting such measurements could be dangerous, some parts were effectively "abandoned" in the past, raising concerns that as-built verification of those areas would be omitted.

• Cumbersomeness of photo organization and document preparation: Compiling as-built photos taken during construction into ledgers and transcribing measurement results into drawings and Excel sheets to create inspection documents was extremely time-consuming. Human errors such as forgotten photos or misplaced photos were also likely, sometimes leading to deficiencies in reports.

As described above, conventional as-built management had issues such as "can only be measured at points", "prone to human error", and "time-consuming to prepare management documents", and these became significant burdens and risk factors for field engineers.

How will as-built management change with the introduction of point cloud data?

As a trump card for solving these issues, attention has focused on the recently widespread 3D point cloud surveying technology. Bolstered by the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* initiative, 3D measurement methods such as drone photogrammetry and terrestrial laser scanners are rapidly permeating job sites. As a result, the use of point cloud data for as-built management is becoming the "new normal." By using point cloud data composed of a large number of measured points, construction outcomes can be captured in a surface-based, highly accurate manner, enabling as-built management that is markedly superior to traditional methods in terms of efficiency, accuracy, and safety.

For example, even at large-scale development sites where traditionally only a few representative cross-sections could be measured, using drone aerial photography plus photogrammetry to generate point clouds allows you to record the entire site in three dimensions without omitting any part. From the acquired point cloud you can freely extract cross-sections at any desired location, or perform analyses such as calculating the distance between any two points and the volumes of embankment and excavation. By scanning once, you can prevent the situation of realizing later that you forgot to take a measurement. Furthermore, because measurements can be taken contactlessly, it is now possible to safely verify the as-built condition of areas that people cannot approach, such as high locations and slopes.

It is clear that leveraging point cloud data dramatically improves the accuracy and comprehensiveness of as-built management, but even more than that, it achieves a revolutionary labor saving in terms of automation of data processing and document creation. Below, let’s take a concrete look at the convenient features unique to point cloud as-built management and their effects.

Visualize as-built conditions at a glance with 3D heat maps

*An example of a heat map that color-codes the differences between the design 3D model and the point cloud as-built. Green indicates within specifications, while red and blue indicate excesses or deficiencies relative to the design.* By overlaying point cloud measurement data and design data, you can create a color-coded heat map that shows "where the surface is higher/lower than the design" and "where thickness is insufficient." It visualizes the differences between the on-site as-built and the design model in 3D, making it immediately obvious whether the deviation from the design value is positive or negative and whether it falls within specifications. For example, in as-built management of roadbeds or concrete thickness, the heat map lets you intuitively grasp even slight surface irregularities across the entire area. Whereas previously pass/fail judgments were made by tracking numbers from tables and cross-sections, simply viewing a colored 3D model allows intuitive understanding, so even less experienced engineers can evaluate as-built conditions quickly and accurately.

Quickly create cross-sectional drawings by extracting arbitrary sections

With point cloud data, it is also easy to extract cross sections at any desired location on site and turn them into drawings. Traditionally, measurements were taken manually for predetermined survey sections, so the number was limited, but with point clouds you can freely analyze locations you decide afterwards that you want to check. For example, even when creating as-built drawings of embankment and excavation cross-sections, you can extract cross-sectional shapes from the point cloud along any arbitrary line in the software and output them directly as CAD drawings or images. Various dimensions such as thickness, width, and height can also be automatically measured on the point cloud, greatly reducing the effort of manual calculation and drafting. Also, tasks such as calculating fill and excavation volumes from the point cloud and creating quantity tables can be completed with the click of a button. As a result, as-built drawing and quantity calculation work that used to take half a day can, in some cases, be finished in a few minutes to several tens of minutes.

Automated Tolerance Determination for Error-Free Pass/Fail Checks

Many point-cloud as-built management software and cloud services have a feature that automatically judges pass/fail of as-built conditions by pre-setting the design specification values (tolerance range). For example, if you enter "the thickness of this member is designed as 20 cm (7.9 in) ±1.0 cm (±0.4 in) as the acceptable range," the system can instantly check whether each measurement point is within the specification by comparing with the point-cloud data. Points that fall outside the specification are displayed in red on a heat map or listed, allowing the person in charge to identify areas requiring correction without overlooking them. Automating pass/fail judgments removes the need for the Excel calculations and drawing-based pass/fail checks that were previously done manually, and greatly contributes to preventing human error.

Significantly reduce administrative work by automatically outputting as-built drawings and forms

Using point cloud data for as-built management dramatically simplifies the document creation process as well. In recent years, cloud-based point cloud processing services have introduced features that automatically generate as-built management charts and forms from point cloud analysis results. For example, the system can output with a single click drawings with heat maps conforming to prescribed as-built management procedures and tables summarizing measurement results (comparison tables of standard values and measured values). *Example: An as-built management report automatically generated in the cloud. A report that integrates a 3D heat map and a comparison table of measured values and standard values.* In this way, the automatic report output feature enables inspection documents that were previously produced through cumbersome tasks—manually entering measurement data into Excel, editing drawings in CAD, pasting photos, …—to be obtained instantly as neatly formatted digital deliverables by leveraging point clouds.

Of course, humans can still make fine adjustments or add comments as needed, but that effort is significantly reduced compared to before. Regarding photos as well, as-built photos taken with smartphones or tablets are automatically uploaded to the cloud with positioning information attached, so they can be managed in an organized manner by date and location. There is no longer any need to paste them into paper ledgers or worry about which photo corresponds to which part. In this way, by introducing point cloud as-built management, the majority of office tasks such as as-built drawing creation, spreadsheets, and photo organization are automated and streamlined, dramatically shortening the time spent preparing inspection documents.

▶ Inspection document preparation work has been streamlined this much! The following are the main examples of tasks that are reduced in effort and accelerated by point cloud as-built management:

• Creation of as-built drawings: Automatically generates drawings by comparing point cloud data with design data. Heat maps and cross-sectional views can also be output with one click.

• Creation of as-built tables and forms: Automatically generates comparison tables of specification values and measured values and pass/fail lists. No manual transcription to Excel is required.

• Organization of as-built photos: Captured images are automatically organized and shared in the cloud. This reduces the effort of creating photo logs and prevents missed shots.

• Preparation of electronic deliverable data: Electronic deliverables, including point clouds, are centrally managed in the cloud. Delivery data formatted according to required data specifications can also be automatically output.

In this way, by introducing point-cloud as-built management, the entire series of tasks involved in preparing inspection documents is streamlined, and a "3x faster" speedup compared with conventional methods has become a realistic prospect.

Real-time Collaboration and Task Distribution through Cloud Sharing

To maximize the power of point cloud data utilization, leveraging a cloud platform is also indispensable. Traditionally, the workflow was "surveying and photographing on site → bringing the data back to the office and processing it on a PC → creating drawings and reports and emailing them to stakeholders", but by using the cloud, "on-site data acquisition → automatic analysis in the cloud → immediate sharing via mobile" enables real-time collaboration.

For example, when photos taken by a drone are uploaded directly from the site to the cloud, point cloud generation and orthomosaic processing begin automatically on the spot. The resulting point cloud data is compared to the design 3D model on the server, and creating heat maps and calculating earthwork volumes are completed in a short time. Site personnel can immediately check the 3D point cloud and cross-sections from a tablet or smartphone, and supervisors and clients can also view the same data on the cloud while in the office. Because everyone can always share the latest as-built information, the time when site decisions are stalled due to "waiting for data" approaches zero. In addition, inspection staff located remotely can review the as-built information online and give immediate instructions, reducing the need for business trips and on-site attendance.

Cloud sharing also promotes distributed work and collaboration. Traditionally, a single person had to carry out tasks sequentially—from surveying through drawing and report preparation—but if data is synchronized in the cloud, work can proceed in parallel: for example, a junior technician measures on site → a senior colleague at the office simultaneously analyzes and checks → a supervisor performs the final review. Large point-cloud datasets can also be distributed to stakeholders via a single shared link through the cloud, eliminating the need to carry them on USB drives or send them by email. Furthermore, leveraging the cloud is effective for electronic delivery of as-built management. Instead of printing and binding large numbers of drawings and photos for submission, delivery can be completed simply by uploading the complete set of data to the cloud and sharing it. This removes the time lag in data verification between clients and contractors and reduces administrative burdens for both parties.

Thus, a workflow that combines point cloud data with the cloud seamlessly connects the field and the office, enabling a speed at which as-built verification and document preparation that used to take several days can be completed within the same day. Because real-time sharing enables early detection and correction of rework, the risk of quality defects is also lowered, and as a result unnecessary work and rework can be reduced, improving overall productivity.

This Is How Much Point Cloud As-Built Management Can Change Things! On-Site Use Cases

As-built management using point cloud data and leveraging the cloud have begun to deliver tangible results at various civil engineering and construction sites. Let's look at some concrete use cases.

• Earthworks (land development, embankment fill, cut-and-fill): Even on sites where survey teams traditionally measured key cross-sections weekly to calculate earth volumes and check as-built conditions, switching to drone photogrammetry + cloud-based point-cloud analysis has achieved major labor savings. Because it captures wide areas as surfaces, there are no unmeasured spots, and as-built checks that used to be conducted once a week can now be performed as needed (for example, immediately after construction), enabling rapid detection and correction of issues during intermediate construction stages.

• Pavement work (flatness and thickness checks): For road paving, it was common to measure finished elevation and asphalt thickness at control cross-sections, but the introduction of point-cloud scanning has made "surface management" possible, allowing evaluation of the entire pavement's flatness with heat maps. If the pavement is scanned immediately after paving, areas with irregularities are instantly color-coded, allowing re-rolling or other corrective work to begin on the spot. As a result, waste from having to redo work after later inspections is reduced, achieving both quality assurance and efficiency.

• Slope works (slope geometry verification): Point-cloud measurement is also effective for verifying the gradient and shape of slopes formed by cutting or filling. Because you can scan the entire slope remotely and without contact, surveyors do not need to climb dangerous faces. By analyzing point-cloud data, you can understand the gradient and irregularities across the whole section from toe to crest, and immediately detect any portion that differs from the design. As a means to both improve safety and strengthen as-built accuracy control, point clouds + heat maps are beginning to be used for slope as-built management.

• Structure works (foundation, superstructure, rebar inspection): For concrete structures such as bridges and retaining walls, setting out foundation positions and verifying rebar placement as-built are important. In addition to point-cloud technology, AR (augmented reality) has recently been combined to achieve the advancement of as-built inspection. For example, displaying the design 3D model in AR on site before construction to streamline setting out, or overlaying the point-cloud of installed rebar with the design model after construction to check for clashes or defects. Because smartphones and tablets can overlay design data onto the real structure, mismatches that are hard to find in drawings alone can be intuitively recognized on site. This is another example of a new as-built management method enabled by the fusion of point-cloud measurement and smartphone technology.

As described above, point cloud-based as-built management is changing the way on-site surveying and inspection are conducted. Tasks that relied on manual labor are being replaced by sensor measurements and automated processing, and aspects that depended on experience and intuition are being transformed into forms anyone can assess through visualization of 3D data. As a result, it has become possible to reduce the burden on each on-site staff member while improving quality.

The Era of LRTK Surveying: Easy for Anyone with a Smartphone and Compact GNSS

Even if you understand the benefits of introducing point cloud as-built management, some people may feel, "It seems difficult to implement that at our site." High-precision 3D measurement has long carried the impression that specialized equipment and advanced skills are required. However, in recent years an innovative tool has appeared that dramatically lowers that barrier. It is a solution that transforms a smartphone into surveying equipment by attaching a small RTK-GNSS receiver.

*An ultra-compact RTK-GNSS receiver for iPhone, "LRTK". A groundbreaking device that turns a smartphone into a surveying instrument capable of centimeter-level positioning (cm level accuracy (half-inch accuracy)).*

The LRTK series developed by Refixia attaches a business-card-sized ultra-compact GNSS unit to an iPhone, turning the smartphone into a surveying instrument compatible with centimeter-level positioning (cm level accuracy (half-inch accuracy)). By combining an antenna weighing several hundred grams with the smartphone and simply launching a dedicated app, the smartphone can determine its own position in real time with an accuracy of 2–3 cm (0.8–1.2 in). Furthermore, if you use the smartphone’s built-in LiDAR scanner and camera to scan the surroundings, every acquired point cloud will be assigned high-precision coordinates, allowing a 3D model of the site to be completed using only the device in your pocket.

By using smartphone surveying devices such as LRTK, as-built measurements that were traditionally performed with a tripod can now be carried out by the site personnel with a smartphone by a single person. For example, by walking around a structure immediately after construction while scanning with an iPhone + LRTK, the point cloud generated on the spot can be compared with the design model in the cloud to confirm whether the as-built condition passes or fails — a series of tasks the site agent can perform themselves without assembling a special surveying team. The acquired data is uploaded to the cloud instantly and can be shared in real time on office PCs or tablets. In other words, to complete everything from surveying to as-built inspection and documentation on-site.

High-precision surveying using a smartphone paired with a compact GNSS receiver (so-called LRTK surveying) significantly lowers the barriers to on-site adoption thanks to its convenience. Because you don’t have to buy expensive dedicated equipment and can make do with your own smartphone combined with a small receiver, initial investment costs can be kept low. Operation is intuitive and so simple that anyone can handle it after just a few minutes of instruction. Even young staff without specialized knowledge of surveying or 3D scanning can quickly master it, contributing to a lift in digital skills across the entire site. You don’t need to worry that “the latest technology can only be handled by veterans.”

Thus, the on-site adoption of point cloud as-built management is no longer something special. With the advent of familiar, smartphone-based tools, an era has arrived in which 3D measurement and cloud utilization can be taken for granted at every site. Point cloud as-built management, which can speed up the traditionally manual creation of inspection documents by up to three times, and LRTK surveying, which makes that easy to implement — these two keywords can be said to be indispensable knowledge for surveying engineers and construction management engineers going forward. As the first step in on-site DX, why not try incorporating them into your company's projects?