Construction & Survey Productivity Improvement Expo Highlight Technology LRTK: Easy 3D Point Cloud Measurement with a Smartphone & Automated Photo Ledger for Site Improvement

The Construction & Survey Productivity Improvement Expo is a specialized exhibition where the latest technologies that enhance productivity in the construction and surveying industries come together. Many solutions that lead to on-site labor savings and DX (digital transformation) are exhibited, attracting project managers, surveying technicians, and municipal infrastructure personnel seeking new information. One of the technologies that drew attention at the exhibition was LRTK. It realizes centimeter-level high-precision positioning, 3D point cloud measurement, and even automated photo record generation using only a smartphone, and has been spotlighted as a solution that directly improves on-site productivity.

This article explains the features and benefits of this innovative technology in an easy-to-understand way for those who missed LRTK at the Construction & Survey Productivity Improvement Expo. We detail what can be done with the simple combination of a smartphone × GNSS, covering positioning, 3D measurement, and AR display functions, and introduce efficient workflows from automatic photo ledger generation to as-built record keeping (shape records at construction completion). We also answer common concerns in a Q&A format, such as “Is the accuracy sufficient?”, “What about communication environments?”, and “How does it integrate with drawing data?” Please read on to learn why the next-generation, easy surveying and recording tool LRTK—startable with a single smartphone—leads to site improvements.

What you can do with smartphone × GNSS! Positioning, point clouds, and AR enabled by LRTK

Traditionally, tasks such as centimeter-precision positioning and high-density 3D point cloud measurement required expensive specialized instruments like total stations or 3D laser scanners and skilled operators. LRTK, however, allows those tasks to be performed with just a smartphone and a palm-sized GNSS receiver. After configuring the positioning augmentation service (RTK) in the dedicated app, all you need to do is walk with the smartphone. Anyone on site can easily perform high-precision surveying and recording. Let’s look at the main functions that LRTK enables.

• Centimeter-level high-precision positioning and stakeout work (cm level accuracy (half-inch accuracy)): By attaching LRTK to a smartphone, real-time kinematic augmentation (RTK) via GNSS becomes available, integrating global navigation satellite data to pinpoint the current position within an error range of a few centimeters (a few in). This enables stakeout tasks such as setting reference points and marking stakes to be done solo with just a smartphone. Tasks that previously required setting up surveying instruments and two-person teams—like confirming stake positions—can now be performed simply by walking and following guide arrows on the screen; the offset between your current location and the target coordinates is shown instantly. When you reach the required location, the smartphone display will indicate “this is the designated point,” allowing you to place a stake or mark on the spot. Because accurate coordinates are always shown on the phone even while walking, you rarely need to stop for positioning.

• 3D point cloud scanning using the smartphone camera: Using the smartphone camera (and LiDAR on high-end models), you can scan a site while walking and quickly acquire high-precision 3D point cloud data. Each point obtained via LRTK is tagged with earth coordinates, so the point cloud has “absolute coordinates” aligned with the survey coordinate system. No complicated operations are required: you just point the camera and walk to digitize terrain and structures. The acquired point cloud can be previewed on the smartphone and used to measure distances, areas, and volumes. For example, you can scan embankments or excavations and immediately calculate volumes, or capture as-built shapes of structures as 3D models and compare them with design models—without specialized measurement equipment.

• On-site projection of design information via AR: Another appeal of LRTK is the ability to overlay design lines and points onto real space on the smartphone screen. Typical smartphone AR functions capture only relative movement, which can cause overlays to drift as you move around the site. LRTK continuously corrects high-precision positional coordinates for AR display, so digital information remains stably aligned with the real object. For example, you can project buried pipe routes or the as-built model of a completed structure onto the site to intuitively check discrepancies with the design. There is also a “coordinate guidance” function that navigates you toward any pre-recorded coordinate with arrow indications, allowing you to locate coordinates from the drawings on site without getting lost. Less experienced workers can quickly find survey points or reference points simply by following the smartphone’s screen instructions.

• Automated recording via geotagged photos: When you take photos with the LRTK app, high-precision coordinate values and camera orientation for the photo’s location are automatically recorded at the moment of capture. All photos are organized in a database with location information, so you won’t need to wonder later “where was this photo taken?” Each photo is linked with latitude and longitude and offset coordinates from reference points, allowing you to verify shooting locations on an electronic map and have them organized as ledger items at capture time. The previously tedious task of creating a photo ledger can be completed with one button, greatly reducing missed photos and recording errors. The risk of forgetting to photograph important spots and needing to retake them later is mitigated because LRTK can automatically check on-site during capture.

Automatic photo ledger generation and as-built record workflow

When LRTK is introduced, the flow from on-site data acquisition to report creation changes dramatically. Previously, survey teams had to measure dimensions point-by-point, take photos, write notes, return to the office to organize and ledger the photos, and compare them with drawings to create as-built inspection documents—a multi-step process. LRTK automates most of these steps and realizes a simple workflow: “Acquire data on site → Organize and analyze in the cloud → Instantly output required forms.” Below is the detailed flow.

• Acquire high-precision data on site: Workers use LRTK attached to a smartphone to measure coordinates of survey points, scan targets, and photograph necessary locations. Each data item is tagged with accurate position information and timestamp at acquisition, so you won’t lose track of data associations later. Instead of writing dimensions with a tape or level, you simply tap “record point,” “start/stop scan,” or “take photo” on the smartphone, and all measurements and images related to as-built conditions are stored digitally.

• One-tap cloud sync: All data acquired on site can be uploaded to a dedicated cloud with a single button from the LRTK app. It automatically syncs over the mobile network, so no special operations or PC transfers are required. Survey data, photos, and point clouds are sent to the cloud in a batch, eliminating the hassle of copying photos via USB or swapping memory cards. Even in areas without signal, uploads can be completed later after moving to a place with reception, so offline environments are supported.

• Automatic analysis and organization in the cloud: Data sent to the cloud is automatically processed on the server. For example, photo data can be converted into a 3D point cloud model using Structure-from-Motion (SfM) algorithms, and LiDAR scan data can be integrated to produce a high-precision point cloud. The system also automatically removes noise points and identifies duplicate photos. If design data (such as designed cross-section models or reference planes) is uploaded to the cloud in advance, the system can immediately compare acquired point clouds and measured coordinates with design values. Heat maps indicating excesses or shortages of as-built conditions and volumetric calculations for embankment/excavation are automatically generated, enabling real-time judgments on site such as “Is this built to design?” or “How many cubic meters of fill are still needed?” Photos are organized by date and location and displayed as an electronic photo ledger.

• Real-time on-site as-built confirmation: Cloud analysis results are viewable immediately from the smartphone on site. Generated point cloud models can be inspected from any angle on the phone, and color-coded heat maps make as-built deviations readily apparent. If any area falls outside the design range, it can be detected and corrected on the spot. Calculated fill/removal volumes can inform adjustments to heavy equipment operations right there. Supervisors and inspectors can review data together on-site, making as-built inspections smoother. Eliminating the wait to “process data back at the office” allows immediate on-site PDCA, which is a major advantage.

• Automatic output of electronic ledgers and forms: Measurement data and photos stored in the cloud can be output directly as electronic forms. For example, as-built management charts and photo ledgers can be exported as electronic files and used as submission documents. Shooting date/time, measurer name, and measured values are filled in automatically, so there is no need to paste photos into ledger templates or transcribe dimensions in the office. Because data is stored in the cloud, you can reprint records if paper copies are lost, and sharing data among stakeholders ensures access to needed information at any time.

Expected benefits of on-site implementation

What effects can be expected when LRTK is actually implemented on site? The main points are “reduction in labor hours,” “improved recording accuracy,” and “smoother downstream processes.” Below we examine each in detail.

Significant reduction in labor hours

LRTK allows a single worker to complete surveying and recording, enabling efficient work even on understaffed sites. For example, reference point staking or as-built measurement that previously required two or more people and half a day can be completed by one person within a few hours with LRTK. Time spent setting up surveying instruments or moving equipment between inspection points is eliminated, and wide-area site conditions can be recorded just by walking and operating a smartphone. Additionally, ancillary tasks such as photo organization and ledger creation are automated, significantly reducing office processing time after fieldwork. Some sites have reported that surveying and recording labor was reduced to less than half compared to previous methods, demonstrating a substantial productivity improvement.

Improved recording accuracy and reliability

Conventional manual management methods were prone to human error. Because LRTK digitalizes and automates data acquisition and organization, recording accuracy and reliability are dramatically improved. The potential for careless human mistakes—such as misreading measurements, transcription errors, missed photos, or incorrect associations—is minimized. All captured values and images retain precise timestamps and coordinates, preventing situations like “not knowing where a photo was taken” or “insufficient inspection documentation due to missing records.” Point cloud data also enables surface-level recording of the entire site, making it easier to detect subtle unevenness or variability in as-built conditions that might be missed by spot measurements. Objective digital records make it easier to substantiate construction details to clients and inspectors, contributing to highly reliable quality verification.

Smooth handover to downstream processes

Data acquired with LRTK is powerful for sharing with downstream teams and related departments. For example, handing over post-construction point clouds and as-built coordinates directly to the design department facilitates smooth electronic submission of drawings and reflection into BIM models. Previously, designers had to re-create CAD drawings from field measurements, but using LRTK data eliminates that redundant work. Likewise, sharing digital as-built data with owners and maintenance personnel supports future inspection and maintenance planning. Rather than handing over paper photo books or massive printed reports, transferring data as electronic files via the cloud ensures information is reliably conveyed. When all stakeholders can view the same up-to-date data, it prevents rework due to misunderstandings or data entry errors and contributes to smoother project execution.

Q&A for those considering implementation

Q: Can LRTK really achieve centimeter-level positioning accuracy? A: Yes. In environments where appropriate satellite augmentation information can be received, LRTK can measure positions at near-centimeter accuracy. Specifically, outdoors with a clear view of the sky and when RTK has achieved a fixed solution, horizontal accuracy falls around ±1–2 cm (±0.4–0.8 in), and vertical accuracy is within ±a few cm (±a few in). Verification results have shown only differences on the order of a few millimeters (a few 0.1 in) compared with conventional high-precision GNSS surveying instruments, so it meets the accuracy demanded on construction sites. However, accuracy can degrade where satellite signals are blocked by tall buildings or dense trees, so it is ideal to use it in as open a sky as possible. LRTK devices also include tilt compensation functionality, so even if the antenna (smartphone) is somewhat tilted during measurement, the system automatically corrects and computes accurate coordinates.

Q: Can it be used in remote mountain areas without mobile connectivity? Will accuracy still be high without network connection? A: LRTK supports not only network-based RTK corrections but, within Japan, also the centimeter-class augmentation service (CLAS) provided by the Quasi-Zenith Satellite System (QZSS) “Michibiki.” Therefore, even in mountain or forest sites without mobile reception, centimeter-class positioning is possible if the CLAS signal from above can be received. In fact, a “no-signal support” option is available for LRTK Phone to enable stable positioning in areas without cellular coverage. However, in environments where satellite signals cannot be received at all—such as inside tunnels or underground buildings—real-time high-precision positioning is unfortunately difficult. In such cases, you may need to measure relative positions from reference points set beforehand or move to a location where GNSS reception is possible. The basic image to keep in mind is that as long as the sky is visible, high-precision positioning is achievable regardless of mobile network availability.

Q: I want to use measured data in our company drawings or CAD— is integration easy? A: Yes, using measured data and comparing it with design drawings is straightforward. The LRTK app allows you to set arbitrary coordinate systems, such as Japan’s plane rectangular coordinate system, so if you configure the site’s coordinate system (survey reference system) in advance, measurement results can be overlaid directly with design drawing coordinates. Design coordinate data (for example, planned as-built positions or structure layout points) can be imported into the app for AR display or used as target points for guidance. Conversely, coordinates measured and recorded on site can be exported as text files such as CSV, and point cloud data can be exported in common formats (LAS or PLY, etc.). Photos are also stored with location information in the cloud and can be plotted on maps or drawings for required outputs. In short, data acquired with LRTK has sufficient compatibility to be imported into various CAD software or GIS systems and to be compared with traditional drawings.

Q: What do we need to implement it? Are special devices or certifications required? A: To use LRTK, you need a dedicated compact GNSS receiver (LRTK device) and a compatible smartphone. Currently, smartphones running iOS (such as iPhone or iPad) are supported; install the dedicated (free) app to use. The LRTK device itself is palm-sized, with an antenna and battery built in, and simply attaches to the smartphone and connects via Bluetooth to be ready for use. After initial setup for required correction services (such as contracting an Ntrip service for network RTK or configuring Michibiki CLAS reception), you can start positioning with one tap in the app. There is no need to set up base stations or obtain radio licenses as with older systems, so you can begin using it on-site immediately after purchase.

Q: Is operation difficult? Can non-experts use it? A: Rest assured. LRTK is designed to be intuitive so that users who are not surveying specialists can operate it. The app interface is simple and clear, and you obtain the necessary data by pressing buttons like “measure point,” “start scan,” or “take photo.” Complex calculations and coordinate transformations are all handled automatically by the system, so users only need to follow the smartphone’s prompts. For example, to record a survey point, press the “positioning” button and the current coordinates are saved; to capture a point cloud, press “start scan,” walk around, and press “stop” to automatically generate 3D data. There are cases where junior staff with no surveying background were able to use LRTK effectively after a short lecture. No difficult equipment operation is required, making it suitable for both veteran field personnel and those less familiar with ICT.

Q: Can it be used in rain or for long-duration work without problems? A: LRTK devices and smartphones are designed to be robust for outdoor use. Typical splash- and dust-resistant measures are applied, so they can normally be used in light rain (for heavy rain or prolonged use in rain, we recommend using a waterproof case as a precaution). As for battery life, the LRTK device’s internal battery typically supports several hours of continuous positioning. Depending on the work, its capacity is usually sufficient for a day’s as-built measurement tasks. The smartphone will consume battery faster than usual due to active use of GPS and camera, but using a mobile battery pack makes it possible to operate for an entire day. On actual sites, LRTK has been run from morning to evening, connecting spare batteries as needed without issues.

Conclusion

The smartphone-based surveying and recording tool LRTK is an attention-grabbing technology with great potential to improve productivity at construction and surveying sites. When it was first shown at exhibitions, there were surprised reactions of “Can that really be done with only a smartphone?” but now it is being adopted at many sites and its effectiveness has been demonstrated. Even small-scale surveying tasks and routine inspections, which were previously avoided due to complexity, can be performed easily and accurately with LRTK, enabling “quick surveys” by site staff themselves. The new style of one smartphone surveying device per person is becoming a common on-site sight, not limited to specialized ICT departments.

Amid initiatives like the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* and broader DX trends, solutions like LRTK are precisely the driving force to “change the field.” Without relying on expensive equipment or complicated processes, anyone can acquire and use accurate data when needed—this enhancement of on-site capability spreads to quality assurance and safety management and, ultimately, raises productivity across the industry. LRTK is expected to expand its use from simple surveying to advanced construction management in various scenarios. If you missed LRTK at the Construction & Survey Productivity Improvement Expo, we hope this article helped you understand its appeal. Please consider adopting next-generation smartphone-based surveying LRTK as part of your site DX promotion.