Construction & Survey Productivity Improvement Expo — Notable Technology LRTK: Easy Smartphone 3D Point Cloud Measurement & Automated Photo Ledger for On-site Improvement

The Construction & Survey Productivity Improvement Expo is a specialized trade show where the latest technologies that enhance productivity in the construction and surveying industries gather in one place. Many solutions that lead to on-site labor savings and DX (digital transformation) are exhibited, attracting construction managers, surveying technicians, and municipal infrastructure personnel looking for new information. One of the technologies that garnered attention at the exhibition was LRTK. Using only a smartphone, it achieves centimeter-level high-precision positioning, 3D point cloud measurement, and even automated photo recordkeeping, drawing spotlight 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 expo. From what is possible with the simple combination of a smartphone × GNSS, and functional overviews such as positioning, 3D measurement, and AR display, to detailed workflows for automated photo ledger generation and efficient as-built recordkeeping (shape records at construction completion), we cover it all. We also answer common questions in Q&A form that arise when considering on-site introduction, 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—which you can start with just a smartphone—leads to on-site improvements.

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

Traditionally, tasks such as centimeter-accurate positioning and high-density 3D point cloud measurement required expensive specialized equipment like total stations or 3D laser scanners and experienced operators. LRTK, however, makes it possible to perform those tasks 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 your smartphone. Anyone on site can easily perform high-precision surveying and recording. Let’s look at the main functions of LRTK and what it can do.

• Centimeter-level high-precision positioning and stakeout work: By attaching LRTK to a smartphone, real-time positioning augmentation (RTK) via GNSS becomes available, integrating global navigation satellite data to determine the current position with an error range of a few centimeters. This enables stakeout tasks like setting reference points and marking stakes to be done solo with a smartphone in hand. Tasks that previously required a two-person team setting up surveying instruments—such as confirming stake positions—can be completed by simply walking following guide arrows on the screen; the deviation between your current position and the target coordinates is displayed instantly. When you arrive at the required location, the smartphone screen shows “This is the required point,” allowing you to place a stake or mark on the spot. Because accurate coordinates are continuously displayed on the phone even while walking, you rarely need to stop for positioning.

• 3D point cloud scanning with a smartphone camera: Using a smartphone camera (and LiDAR on high-end models), you can scan the site while walking and quickly obtain high-precision three-dimensional point cloud data. Each point acquired with LRTK is tagged with geodetic coordinates, so the point cloud data contains “absolute coordinates” aligned with surveying coordinate systems. No complicated操作 is required—point your camera and walk to digitize terrain and structures entirely. The acquired point cloud can be viewed on the smartphone screen and used for distance, area, and volume measurements. For example, you can scan embankment or excavation as-built conditions to instantly calculate volumes, or capture the post-construction shape of a structure as a 3D model and compare it with the design model—all without specialized measurement equipment.

• On-site projection of design information via AR: Another attraction of LRTK is that when you hold up the smartphone, lines and points from the design drawings can be overlaid on the real world on the screen. Typical smartphone AR functions only capture relative movement, causing overlays to drift as you walk around. LRTK, however, continuously corrects with high-precision position coordinates, keeping digital information stably aligned with the actual object. For example, you can project routes of buried pipes or completed structural models onto the site to intuitively check discrepancies with the design. There is also a “coordinate guidance” feature that navigates toward any pre-recorded coordinate with arrow indications, allowing target coordinates from drawings to be located on site without confusion. Even inexperienced workers can quickly find survey points and reference points by following on-screen instructions.

• Automated recordkeeping with geotagged photos: When taking photos with the LRTK app, high-precision coordinates and camera orientation at the moment of shutter release are automatically recorded. All photos are organized in a database with location information, eliminating the need to wonder later “Where on site was this photo taken?” Each photo is linked with latitude/longitude and offset coordinates from reference points, enabling verification of shooting locations on an electronic map and organization into ledger items at the time of shooting. The cumbersome task of creating a photo ledger can be completed with the push of a button, greatly reducing missed photos and recording errors. The risk of having to rush back later to retake critical photos is mitigated by LRTK’s automatic on-site checks at the time of shooting.

Automated photo ledger generation and as-built record workflow

Introducing LRTK significantly changes the flow from on-site data acquisition to report preparation. Previously, the survey team had to measure dimensions point by point, take photos and notes, return to the office to organize photos into ledgers, and cross-check drawings to prepare as-built inspection documents—a multi-step process. LRTK automates nearly the entire sequence, realizing a simple workflow: “Acquire data on site → Organize and analyze in the cloud → Instantly output required forms.” Below is the specific flow.

• Acquire high-precision data on site: Workers use the LRTK attached to a smartphone to measure survey point coordinates, scan target objects, and photograph required locations. Each datum is tagged with accurate position information and timestamps at acquisition, so there is no worry about losing the association between data later. Instead of writing dimensions with a tape or level, you simply tap “record point,” “start/stop scan,” or “take photo” on the smartphone to store all as-built measurements and images as digital data.

• One-tap cloud sync: All data acquired on site can be uploaded to the dedicated cloud with a single button from the LRTK app. Data syncs automatically over the mobile network, removing the need for special operations or PC transfers. Survey data, photos, and point clouds are all sent together to the cloud, eliminating the hassle of copying photos via USB or swapping memory cards. In areas without signal, uploads can be performed later once you move to a location with reception, so offline environments are not a problem.

• Automatic cloud-side analysis and organization: Data sent to the cloud undergoes automatic server-side processing. 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 generate high-precision point clouds. The system also automatically removes unnecessary noise points and identifies duplicate photos. If you upload design data in advance (such as as-built design cross-section models or reference planes), the system can immediately compare acquired point clouds and measured coordinates with design values. Heat maps indicating as-built excesses/shortages and earthwork volume calculation results for fill/excavation are automatically generated, enabling real-time on-site judgments like “Is this according to the design?” or “How many more cubic meters of fill are needed?” Photos are organized by date and shooting location and displayed as an electronic photo ledger.

• Real-time on-site verification of as-built conditions: Cloud analysis results can be viewed immediately from the on-site smartphone. Generated point cloud models can be examined on the phone from any angle, and color-coded heat maps show as-built deviations at a glance. If any area falls outside the design range, it can be detected on the spot and corrected immediately. Decisions such as adjusting heavy equipment work based on calculated fill or removal volumes can be made on site. Supervisors and inspectors can review data together on the spot, smoothing as-built inspections. The wait time of “process data at the office later and then determine” disappears, enabling immediate PDCA cycles on site—a major advantage.

• Automatic output of electronic ledgers and forms: Measurement data and photos stored in the cloud can be output directly as digital forms. For example, as-built control charts and photo ledgers can be exported as electronic files and used as submission documents. Shooting timestamps, measurer names, and measured values are automatically populated, removing the need to paste photos into ledger templates or transcribe dimensions in the office. Since data is stored in the cloud, forms can be reprinted if paper records are lost, and sharing data among stakeholders ensures that necessary information is always accessible.

Expected effects when introduced on site

What effects can be expected when LRTK is actually introduced on site? The main points are “reduction of work hours,” “improvement in recording accuracy,” and “smoothness of downstream processes.” Let’s look at each in detail.

Large reductions in work hours

Because LRTK allows a single worker to complete surveying and recordkeeping, it enables efficient operations even on labor-short sites. For example, reference point setting or as-built measurements that used to take two or more people half a day can sometimes 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 areas can be recorded simply by walking and operating the smartphone. Ancillary tasks like photo organization and ledger creation are also automated, significantly reducing post-site administrative time. Some sites have reported reducing surveying and recording work hours to less than half compared to previous methods, demonstrating a substantial productivity improvement.

Improved recording accuracy and reliability

Traditional manual management methods are inevitably accompanied by human error risks. Because LRTK digitalizes and automates data acquisition through organization, recording accuracy and reliability improve dramatically. Errors such as misreading measurement values, transcription mistakes, missed photos, or incorrect links between photos and locations are minimized. All acquired numbers and images retain accurate timestamps and coordinates, preventing problems like “I don’t know where this photo was taken” or “record gaps causing insufficient inspection documents.” Moreover, point cloud data records the site comprehensively, making it easier to detect subtle unevenness or variations in as-built conditions that point-only measurements might miss. The existence of objective digital records also makes it easier to substantiate施工内容 to clients or inspection bodies, contributing to high-trust quality assurance.

Smooth handover to downstream processes

Data obtained with LRTK is also powerful for information sharing with downstream processes and related departments. For example, handing point cloud data or as-built coordinates to the design department allows smooth electronic delivery of drawings or reflection into BIM models. Previously, designers had to redraw numbers measured on site into CAD, but LRTK data eliminates that duplication. Similarly, sharing the completed digital data with clients or maintenance managers supports future inspection and maintenance planning. Instead of handing over paper photo books or voluminous reports manually, electronic data via the cloud ensures reliable information transfer. Because all stakeholders can view a common up-to-date dataset, this prevents “rework due to miscommunication” and “losses from data entry errors,” contributing to smoother project progress.

Q&A for prospective adopters

Q: Can LRTK really achieve centimeter-level positioning accuracy? A: Yes—when receiving appropriate satellite augmentation information, LRTK can measure positions with nearly centimeter-level accuracy. Specifically, in open outdoor environments where RTK achieves a fixed solution, horizontal accuracy is approximately ±1–2 cm, and vertical accuracy is within several centimeters. Validation results have shown differences of only a few millimeters compared to conventional high-precision GNSS surveying equipment, meaning it meets the accuracy required on construction sites. However, accuracy can degrade in environments where tall buildings or dense trees block satellite signals, so using it in as-open-a-sky environment as possible is ideal. LRTK devices also include tilt compensation, so accurate coordinates are calculated automatically even if the antenna (smartphone) is tilted somewhat during measurement.

Q: Can it be used in mountainous areas with no mobile signal? Will it still provide high accuracy without network connection? A: LRTK supports not only network-based RTK corrections but also Japan’s quasi-zenith satellite Michibiki (QZSS) centimeter-class augmentation service (CLAS). Therefore, even in mountain or forest sites without cellular coverage, centimeter-level positioning is possible if CLAS signals from the sky can be received. In practice, the LRTK Phone offers an “offline/coverage-outage” option, enabling stable positioning even in areas without cellular coverage. On the other hand, in tunnels or underground where satellite signals cannot reach, real-time high-precision positioning is unfortunately difficult. In such cases, you must measure relative positions from reference points in advance or move to a location where GNSS reception is available. In short, if you can see the sky, expect high-precision positioning regardless of network availability.

Q: I want to use measured data in our company drawings or CAD— is integration easy? A: Yes, using acquired 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 align the app with the site’s coordinate system in advance, measurement results can be directly overlaid on design coordinates. If design coordinate data (e.g., planned as-built positions or structural arrangement points) is available, you can import it into the app for AR display or use it as target points for the guidance function. Conversely, measured and recorded point coordinates can be exported as text data such as CSV, and point clouds can be exported in common formats (LAS, PLY, etc.). Photos are stored in the cloud with location information, allowing you to output ledger reports that plot images on maps or drawings. In short, data obtained with LRTK has sufficient compatibility to be imported into CAD software or GIS systems and to be compared with conventional drawings.

Q: What is required to introduce it? Are special devices or qualifications needed? A: To use LRTK you need a dedicated small GNSS receiver (LRTK device) and a compatible smartphone. Currently, smartphones running iOS (such as iPhone or iPad) are supported, and a dedicated (free) app is installed for use. The LRTK device itself fits in the palm of your hand, has an integrated antenna and battery, and is ready to use by attaching it to the smartphone and connecting via Bluetooth. After initial settings for correction information required for positioning (such as an Ntrip RTK service contract or Michibiki CLAS reception settings), 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 traditional systems, so you can begin using it on site immediately after purchase.

Q: Is it difficult to operate? Can non-experts handle it? A: Rest assured. LRTK is designed to be intuitive even for non-specialist users. The app interface is simple and easy to understand—just press buttons like “measure point,” “start scan,” or “take photo” to acquire the necessary data. Advanced calculations and coordinate conversions are handled automatically by the system, so users only need to follow the smartphone prompts. For instance, to record a survey point you simply press the “positioning” button to save the current coordinates, and to capture a point cloud you press “start scan,” walk around, and press “stop” to generate the 3D data automatically. There are company examples where junior staff without surveying expertise were able to use LRTK effectively after a short lesson. Because complicated equipment operations are unnecessary, it is usable by a wide range of personnel—from experienced veterans to those less familiar with ICT.

Q: Can it be used in rainy weather or for long-duration tasks without problems? A: The LRTK device and smartphones are designed to be robust for outdoor use. They generally have splash-proof and dust-proof measures, so they can be used in light rain (for prolonged heavy rain use, we recommend protective measures such as waterproof cases). The LRTK device’s internal battery supports several hours of continuous positioning. Depending on task specifics, the typical daily as-built measurement workload can be covered by one full charge. The smartphone’s battery will drain faster due to active GPS and camera use, but using an external mobile battery can support all-day operation. In practice, sites have run LRTK from morning to evening with occasional connection of spare batteries without problems.

Conclusion

The smartphone-based surveying and recording tool LRTK offers great potential to improve productivity at construction and surveying sites. When first shown at exhibitions, many asked “Can that really be done with just a smartphone?” but now many sites have implemented it and demonstrated its effectiveness. Tasks that were avoided with traditional methods—small-scale surveys and routine inspections—can now be performed easily and accurately by site staff using LRTK. The new style of “one smartphone per person” surveying is becoming a common sight on site, not limited to specialized ICT departments.

Within the i-Construction and DX initiatives promoted by the Ministry of Land, Infrastructure, Transport and Tourism, solutions like LRTK are precisely the drivers that “change the field.” Without relying on expensive equipment or cumbersome processes, anyone can obtain and utilize accurate data when needed—this improvement in on-site capability spreads to quality assurance and safety management and, ultimately, raises the industry’s overall productivity. LRTK is expected to expand its applications from simple surveying to advanced construction management. If you missed LRTK at the Construction & Survey Productivity Improvement Expo, I hope this article helped you understand its appeal. Consider introducing next-generation smartphone-based surveying LRTK as part of your on-site DX push.