LRTK for Solo Surveying: A Next-Generation Workflow Eliminating Traditional Survey Teams

In recent years, a new trend called "solo surveying" has begun to emerge in construction and civil engineering field surveys. This approach aims to complete surveying tasks that traditionally required multiple people by leveraging cutting-edge technologies. One solution attracting particular attention is the high-precision positioning system "LRTK," which combines a smartphone with a compact GNSS device. By attaching an ultra-compact RTK-GNSS receiver to a handheld device such as an iPhone, anyone on site can perform centimeter-level surveying and layout marking. This article explains the background and challenges of solo surveying, the technical features of LRTK (positioning, point clouds, AR, navigation), comparisons with traditional methods, and how it transforms on-site workflows from a professional perspective. Aimed at construction managers, civil engineers, and municipal infrastructure personnel, it details practical use cases, benefits, and pricing structure, and concludes with a simple operational example of solo surveying using LRTK.

Labor Shortages and the Rise of "Solo Surveying"

Surveying is an indispensable process for quality control and as-built verification at construction and infrastructure maintenance sites. However, the industry currently faces a severe labor shortage. With veteran surveyors aging and fewer young professionals entering the field, limited personnel must cover many sites. In addition, the enforcement of workstyle reform-related laws in 2024, which impose restrictions on overtime work (the so-called 2024 issue), has increased the need to perform surveying tasks efficiently within limited time and manpower.

Traditional surveying work assumed a multi-person team. For example, when using a total station, one person operates the instrument while another holds a prism at a distant survey point—typically a two-person team. In some cases a third person records the measured points, making surveying labor- and time-intensive for sites. On large sites with many points, preparation through teardown could take an entire day, and the inefficiency of not being able to use data immediately in the office for drafting and quantity calculations was also a problem. Manual measurement is also prone to human error; misreading or recording mistakes can lead to rework in downstream processes and schedule delays. Relying on a few experienced individuals creates a single point of failure—if the responsible person is absent, the site can stall waiting for surveying.

As a solution to these challenges, "solo surveying" is gaining attention. By leveraging the latest digital technologies (high-precision GNSS and AR), surveying that once required multiple people can potentially be performed accurately and quickly by a single person. The Ministry of Land, Infrastructure, Transport and Tourism-led *i-Construction* initiative (promoting ICT use on construction sites) has also given momentum to this approach, and solo surveying is being noted as a next-generation workflow to reduce onsite manpower and improve efficiency.

What is LRTK: Redefining Surveying Equipment with a Smartphone

A representative solution that has made solo surveying practical is LRTK (developed by Reflexia). LRTK is an ultra-compact RTK-GNSS receiver designed to attach to a smartphone. Its pocket-sized housing contains a high-performance antenna and battery, weighing about 125 g and with a thickness of about 1 cm (0.4 in). It can be easily attached to an iPhone/iPad via a dedicated smartphone case and connects to the phone via Bluetooth or Lightning. This turns an everyday smartphone into a centimeter-level precision surveying instrument.

High-precision positioning mechanism: LRTK corrects the meter-level errors of standalone smartphone GPS down to a few centimeters using the RTK method. It supports network RTK (e.g., the Geospatial Information Authority of Japan’s Continuously Operating Reference Stations and commercial correction services), receiving correction data from reference stations to improve real-time positioning accuracy. Once powered and acquiring satellites, a FIX solution with errors of a few centimeters is obtained in a short time, allowing work to start without long waits. LRTK also supports the CLAS signal provided by Japan’s Quasi-Zenith Satellite System—a centimeter-class positioning augmentation service—so standalone cm-level accuracy (half-inch accuracy) positioning is possible even at sites where cellular signals do not reach, such as mountainous areas. High-precision surveying that once required tripod-mounted large instruments and specialist knowledge can now be handled by anyone with a palm-sized device.

Smartphone app and cloud integration: When using LRTK, you start a dedicated smartphone app (iOS/Android) to begin positioning. The app automates advanced settings, making operation intuitive and enabling one-touch recording, calculation, and saving of survey points. For example, conversions to the plane rectangular coordinate system and geoid height calculations can be performed automatically during measurement, and each point can be saved with a name or note—eliminating the need to write coordinates in a paper field book. Collected data is stored on the smartphone and can be uploaded to the cloud (LRTK Cloud) with one button, allowing real-time review and sharing from office PCs. Conversely, if design drawings, coordinate lists, or 3D models are uploaded to the cloud in advance, the site smartphone can sync with them, enabling onsite comparison of design data and as-built survey data. In this way, LRTK functions as an all-in-one surveying system based on smartphone + cloud.

Comparison with Traditional Surveying: What Changes and How

Here are the main points of improvement brought by modern smartphone surveying (LRTK adoption) compared to traditional methods.

• Reduction in required personnel: Surveying tasks that used to require 2–3 people can be completed by one person with a smartphone + high-precision GNSS. This reduces labor costs and prevents surveying delays at sites with staff shortages.

• Simplified equipment and setup: Transporting and setting up large equipment such as total stations, staffs, and levels is unnecessary. A pocketable smartphone and LRTK suffice, eliminating the need to carry heavy tripods and enabling immediate work upon site arrival.

• Work efficiency and speed: Previously the workflow—from surveying to drafting to quantity calculation to as-built verification—could take days, but the new approach allows onsite data to be shared to the cloud and results to be checked immediately. Real-time understanding of as-built status helps prevent rework.

• Positioning accuracy and quality assurance: Concerns like "Is it safe to survey alone?" are addressed by LRTK’s RTK method, which achieves high-precision positioning with errors of a few centimeters. It is more accurate than tape measures or standalone GPS, meeting quality control requirements. Higher precision reduces re-measurements and rework, improving the reliability of as-built management.

• Data recording and error prevention: In digital surveying, measurements and photos automatically record location information, removing the need for handwritten transcriptions. Photos include coordinate and orientation tags, so there’s no worry about losing track of where a photo was taken later. Human recording errors decrease, preventing data mix-ups or omissions.

• Ease of learning and standardization of work: Smartphone app-centric operation is simple and intuitive. Even those with limited experience handling advanced surveying instruments can learn to use it quickly. Because surveying know-how is centralized in the app, anyone can work with consistent accuracy, reducing reliance on specific veterans. This eliminates person-dependent variability and enables the team to maintain stable surveying quality.

From the above comparisons, it should be clear that solo surveying makes it possible to "obtain high-precision data rapidly with fewer personnel and put it to immediate use." The diverse feature set of LRTK, described next, is the key to making this a reality.

Main LRTK Functions (Positioning, Point Clouds, AR, Navigation)

LRTK is more than just a positioning device; it integrates various functions that leverage the smartphone’s camera and sensors. As a single device it supports "measuring, recording, guiding, and visualizing," aiding on-site digital transformation. Below are four particularly important features.

• High-precision positioning (GNSS positioning): The core function of LRTK is centimeter-precision coordinate measurement. RTK-GNSS provides real-time high-precision latitude, longitude, and height, and measured point data can be saved on the smartphone and immediately uploaded to the cloud. A FIX solution is often obtained within just tens of seconds of starting positioning, and required points can be saved with a single button on the smartphone screen. Measured coordinates are automatically converted to Japan’s plane rectangular coordinates and geoid height, enabling direct onsite comparison with design drawings without post-processing.

• Point cloud data acquisition (3D scanning): By combining iPhone/iPad LiDAR scanners with high-precision position information, you can capture the site’s three-dimensional shape as point cloud data. For example, scanning structures or terrain with a smartphone generates a colorized point cloud model viewable on the phone immediately. Point clouds that used to require a dedicated laser scanner and PC processing can be scanned and digitized onsite with LRTK, then sent to the office via cloud if needed. From acquired point clouds you can instantly measure distances, areas, and volumes on the smartphone, greatly streamlining as-built management and quantity estimation.

• AR display and stakeout assistance (augmented reality): LRTK overlays virtual objects on the site using AR based on measured coordinates and design data. Selecting a target point on the design will display a virtual stake or line in the corresponding position in the smartphone camera view. It’s as if the completed structure or marking has been drawn at the site through the camera, enabling intuitive actions like "drive a stake here" or "fill to this height." For stakeout, novices can place stakes accurately by following guidance on the smartphone without needing an experienced surveyor. AR stakes remain fixed in the prescribed position regardless of viewpoint, so there is no displacement concern, and AR-based position confirmation is useful where physical stakes cannot be placed, such as on concrete or in hazardous areas.

• Coordinate navigation (guidance): Using the GNSS-derived current position relative to a target coordinate, the LRTK app can navigate the user to a desired point. Selecting a design coordinate or a previously recorded survey point displays an arrow indicating direction and distance on the smartphone screen, guiding the user like a car navigation system to the precise location. As you approach, the display switches to an AR guidance view for precise alignment. This prevents wasted walking to find points on large sites and enables newcomers to reach targets reliably. Registering coordinates in advance is also helpful for locating buried utilities or conducting disaster damage assessments—anyone can reach required locations reliably, aiding rapid field response.

As shown above, LRTK provides all-in-one functionality from positioning and measurement to navigation, recording, and visualization. With this single device, tasks that previously required a surveying specialist can be handled by site personnel, enabling more agile site management.

Workflow Changes with Solo Surveying: Complete with a Single Smartphone

With LRTK, surveying through construction management workflows changes significantly. The key point is that a single person can seamlessly perform "site arrival to data sharing, stakeout, inspection, and record-keeping."

• High-precision as-built surveying: Upon arrival, attach the LRTK device to the iPhone and start the dedicated app. After satellite acquisition, connect to reference station corrections (via network or CLAS) and begin RTK positioning. When the status reaches FIX (errors of a few centimeters) within tens of seconds, surveying is ready. Hold the smartphone (or the detached LRTK antenna) over the point to be measured and tap the screen button to record the coordinate instantly. You can also scan surrounding areas with the iPhone LiDAR to obtain point cloud data as needed. Collected as-built data is saved on the device and can be uploaded to the cloud with one tap.

• Immediate data sharing via the cloud: Points and point clouds synced to the cloud can be viewed on maps in real time from the office—no need to wait for the surveyor to bring data back on a USB drive. The site and office remain continuously connected via data. Conversely, if coordinate lists or 3D models of the construction drawings are uploaded to the cloud in advance, the site smartphone will automatically sync them. Cloud-side automated alignment of design data and as-built point clouds removes the need for cumbersome onsite coordinate matching. This realizes seamless information sharing between site and office.

• Positioning via navigation: Move to stakeout or reference point tasks by selecting the target point in the LRTK navigation feature; an arrow and distance are displayed on the smartphone screen, and you follow its guidance. As you get close, the display switches to the AR guide, which steers you to centimeter-level alignment. Where workers once searched for stakeout locations based on drawings or batter boards, smartphone navigation lets them reach targets without hesitation. Even those with limited surveying experience can reliably identify points, so stakeout can be performed without veteran accompaniment.

• Layout marking and stake driving with AR: When at the designated location, switch to AR mode and point the camera. Virtual stakes and marking lines appear at the specified coordinates in the view. For example, for a stakeout point the screen shows a CG stake inserted into the ground; the worker then drives the actual stake at the spot directly beneath it. Visual AR stakes allow a single worker to complete layout marking quickly and accurately without an assistant. For sites that are unsafe or inaccessible (e.g., mid-slope), virtual stakes can be displayed from a safe position to indicate locations, greatly improving efficiency and safety.

• As-built inspection and on-site feedback: LRTK is also powerful for post-construction as-built inspections. With a smartphone in hand, measure heights and shapes at inspection points and upload the measurements to the cloud immediately. Design values are already synced from the cloud, so measured points are recorded in the design coordinate system and deviations are calculated instantly. For example, checking pavement subgrade elevation becomes as simple as uploading measured elevations to receive an immediate discrepancy list. If out-of-spec areas are found, additional measurements or correction work can be performed on site to minimize rework. For broad coverage, scan as-built shapes with point clouds and later overlay them with the design 3D model for comprehensive verification. All data is stored in the cloud, facilitating report generation.

• Photo records and maintenance management applications: LRTK is also useful for routine inspections and organizing construction record photos. Photos taken with the smartphone are automatically tagged with coordinates and camera orientation, removing the need to scribble photo locations on paper drawings. Photos appear on a cloud map, making later retrieval effortless. For periodic inspections, registering photo locations enables re-shooting from the exact same position and angle using navigation—improving the accuracy of comparative aging analysis and enhancing the reliability of infrastructure inspections.

As described, LRTK allows a single technician to perform surveying, stake driving, as-built verification, and photo documentation end-to-end. Onsite data is shared in real time, enabling immediate decisions and follow-up instructions. Free from paper forms and Excel-based management, everyone accesses the same cloud information, reducing tacit knowledge dependence. The result is smoother construction management without waiting times and improved standardization, significantly boosting overall site productivity.

Specific Use Cases and Benefits

By practicing solo surveying, you can realize the following benefits across various scenarios.

• Improved efficiency for stake driving: Tasks such as establishing reference points and setting batter boards traditionally required a surveying crew to locate points before workers drove stakes. With LRTK, workers can view AR stakes on their smartphones and drive stakes into the correct positions themselves. Even where physical access is difficult—such as slopes or high locations—virtual stakes shown from a safe position identify points, smoothing temporary sign placement. Labor and steps are reduced, greatly improving construction sequencing.

• Reduced labor for as-built inspection: Post-completion inspections and as-built surveying can be completed rapidly by one person using LRTK, from measurement to recording. For example, in checking pavement elevations, a single worker can measure each point with a smartphone and upload to the cloud to obtain an immediate error list for all points. Tasks that used to require multiple people and a full day are dramatically shortened, and onsite correction becomes possible, improving inspection accuracy and reliability.

• Digital transformation of inspection records: For infrastructure inspections and construction records, simply photographing with a smartphone auto-tags high-precision coordinates and orientation, organizing photos on a cloud map. This eliminates the need to write photo locations on paper drawings and the later sorting work, and ensures reproducibility of shooting positions—making comparative analysis and report generation more accurate and efficient. This contributes to DX promotion by preventing inspection omissions and reducing record-keeping labor.

• Support for novices and emergency response: LRTK’s navigation function enables inexperienced staff to reach target points without hesitation. They can quickly locate survey points in a new site or share coordinates of damaged areas immediately after a disaster to rapidly deploy site surveys, strengthening field response capability. This reduces reliance on veteran intuition and serves as an effective backup system in training and emergency situations.

From these use cases, it is clear that LRTK as a solo surveying tool is more than efficiency improvement: it can fundamentally change how construction progresses. Besides labor reduction, there are additional benefits such as improved safety, accuracy, and advanced data utilization.

Implementation Costs and Pricing Structure: High-Precision Surveying within Reach

Cost is a major concern when adopting new technologies. Traditional high-precision surveying instruments—whether total stations or GPS receivers—can be expensive, and a complete set of large laser scanners or professional drone systems can cost several million yen just for the hardware. In contrast, smartphone surveying with LRTK dramatically reduces initial costs.

Initial investment: If you already have a LiDAR-equipped smartphone (e.g., iPhone 12 Pro or later), you only need the device hardware. Even if acquiring the smartphone, a complete smartphone + GNSS device setup is typically on the order of several hundred thousand yen. For example, equipping a personal iPhone with an LRTK device allows you to start high-precision surveying for several hundred thousand yen—an order of magnitude lower than standalone 3D laser scanners or drone surveying systems that cost several million yen—making it affordable for small and medium-sized enterprises.

Operating costs: Correction information required for positioning in Japan can utilize the Quasi-Zenith Satellite System’s CLAS signal, which is free. If LRTK supports CLAS reception, high-precision positioning is possible without additional fees. For network RTK (Ntrip) services over cellular networks, commercial correction subscriptions are available from a few thousand yen per month. Thus, running costs are relatively low and allow flexible plan selection according to needs. LRTK’s cloud services and dedicated app fees vary by product—monthly subscription plans or lifetime plans including device purchase are available—allowing flexible choices to match organizational operations.

Return on investment: Solo surveying can reduce labor costs and shorten project schedules, leading to cost savings. For example, halving the surveying personnel from two to one cuts personnel costs substantially, and eliminating machine idle time due to waiting for surveying reduces opportunity loss. Reducing errors that cause rework or additional investigations also yields significant qualitative benefits. Given the relatively small initial investment, LRTK implementations often achieve short payback periods. Overall, LRTK represents "affordable site DX."

Example Operation of Solo Surveying with LRTK

Finally, to show how simple solo surveying with LRTK can be, here is an example operation flow for “a single person performing reference point surveying and stakeout layout marking.”

• Device attachment and start positioning: On arrival, attach the LRTK device to the iPhone and power it on. Launch the dedicated app and configure satellite correction reception (network connection or CLAS). In about 20–30 seconds, the RTK status becomes FIX (±2 cm (±0.8 in) accuracy). High-precision positioning is now ready.

• Measuring reference points: Hold LRTK over a known point or a chosen point and tap the app’s positioning button to record coordinates. Latitude, longitude, and height are saved instantly, and you can add a point name or note. Recorded points are automatically synced to the cloud so they can be checked from the office PC (if out of range, upload manually later).

• As-built surveying (point cloud acquisition as needed): Proceed to measure required points around the site alone. Simply aim the smartphone at each point and press the button to capture coordinates one after another. If vertical measurements are needed, attach LRTK to an accessory monopod (pole) and place the tip on the ground for accurate ground elevation. At key locations, run iPhone LiDAR scans to obtain point cloud data for later use.

• Importing design data: Call up pre-uploaded design coordinates and drawing data in the app and select target points for stakeout or checks. For instance, if a list of design coordinates for stakes is prepared, choose one target. With design values synced via the cloud, target information is set on the smartphone with this operation.

• Navigation and AR stakeout: Press the navigation start button and follow the arrow and distance displayed on the smartphone to move toward the target. When approaching the destination, switch to AR mode. A virtual stake (AR marker) appears at the specified coordinate in the camera view. Adjust your standing position so the virtual stake appears properly embedded in the ground; that point is the stakeout location. Mark the spot and drive the actual stake there. This completes accurate solo stake positioning.

• As-built confirmation and recording: After stake driving, verify the surrounding as-built conditions. For example, measure the top of the stake or pavement elevation with LRTK. Measured points are immediately displayed on the smartphone, and the difference from preloaded design elevations is calculated automatically. Check whether values are within tolerance on site and, if acceptable, complete the task. Finally, take a few photos for records; photos are coordinate-tagged so their locations are instantly identifiable later.

All of the above steps can be performed by one person with a single smartphone—this is the strength of solo surveying with LRTK. Tasks that once required multiple personnel and days of work are completed in a few simple steps, enabling construction managers to perform necessary surveying and inspections at the needed times, dramatically improving site productivity and mobility.

Amid labor shortages and workstyle reforms, the realization of solo surveying is a major boon for the construction and civil engineering industries. The next-generation workflow enabled by LRTK allows high-precision surveying with a small crew, transforms on-site management through real-time information sharing and workflow standardization, and eliminates inefficiencies such as waiting for surveys or rework while achieving both quality assurance and DX promotion. With surveying tasks—once requiring technical expertise—replaced by intuitive smartphone operations, the norms of the field are changing dramatically. Consider adopting solo surveying with LRTK to update traditional workflows and take your site to the next stage with the support of the latest technology.