Table of Contents

• Easy 3D scanning starting with iPhone

• Challenge: smartphone alone lacks sufficient accuracy

• Improving positioning accuracy with RTK technology

• Domestic LRTK turns iPhone into a surveying instrument

• Centimeter-level point cloud measurement enabled by iPhone 3D scanning + LRTK

• Practical uses of iPhone point cloud measurement on site

• Comparison with conventional technologies and advantages

• Conclusion: on-site transformation through simple surveying with LRTK

The era in which high-precision 3D measurement can be performed with a single smartphone has arrived. By combining the iPhone’s 3D scan capability with the domestically developed positioning technology LRTK, anyone can now easily acquire centimeter-level point cloud data that previously required dedicated, expensive equipment. Measurement work on job sites is undergoing a major change.

Traditionally, precision surveying and 3D measurement were performed by skilled technicians using expensive equipment such as total stations or laser scanners. Recently, however, the wave of digital transformation (DX) has reached the construction industry, and on-site measurement methods are changing dramatically. As promoted by the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative, work-efficiency improvements using ICT are being pushed forward, and easy 3D scanning with smartphones is expected to be a strong solution for on-site DX. Now, the smartphone that everyone has is becoming the star of surveying.

Easy 3D scanning starting with iPhone

Recent iPhone and iPad Pro models include compact LiDAR (light detection and ranging) scanners, making 3D scanning easy to perform. Using dedicated apps, you can simply point the device at surrounding spaces or objects to scan and record them as 3D models or point cloud data. Tasks such as measuring room dimensions or creating 3D models of objects for AR display, which once required specialized equipment or professional service providers, are now possible with just a smartphone. The ability to handle three-dimensional data on a palm-sized device has attracted attention across many fields, from construction and design to entertainment.

Efforts to leverage smartphones for high-precision positioning have begun overseas as well, but cases that integrate positioning up to 3D scanning like LRTK are still relatively rare. The domestically developed LRTK can be considered an advanced solution even on a global scale.

In fact, the App Store offers numerous apps for spatial scanning and 3D modeling, and a diverse range of users—from professional architects to hobbyists—are beginning to use iPhone 3D scanning. The convenience of performing precision measurements and creating 3D data that once required specialized equipment with just a smartphone is truly revolutionary.

※ Note: point cloud scanning features are available on iPhone and iPad Pro models equipped with LiDAR. For higher-precision measurements, devices with the latest sensors (e.g., iPhone 15 Pro) are recommended.

Challenge: smartphone alone lacks sufficient accuracy

While iPhone 3D scanning is convenient, there are several accuracy-related issues when using it directly for surveying. First, point cloud data acquired by a smartphone alone is not assigned absolute coordinates. The generated 3D data remains in a local coordinate system, so its location on a map is unclear. For example, even if you scan a site’s terrain, unless that point cloud is linked to actual latitude/longitude or known control points, it becomes difficult to compare it with design drawings or integrate it with other survey data.

Second, because the smartphone relies only on its internal sensors for position tracking, errors tend to accumulate when walking while scanning over wide areas. Over time, the device’s self-position estimates can drift, often causing distortions in flat surfaces such as the ground. If you scan a large area continuously, the point cloud can gradually shift and ultimately misrepresent the actual shape.

Thus, iPhone 3D scanning has inherent limits in terms of positioning accuracy in exchange for its convenience. In civil engineering and construction sites where centimeter-level accuracy is required, it is currently difficult to directly use measurement data from a smartphone alone. So how can we dramatically improve the accuracy of smartphone-based 3D scanning?

Improving positioning accuracy with RTK technology

The key is RTK (Real Time Kinematic) technology, which corrects satellite positioning errors to achieve precise locations. Typical GPS-based position information that we commonly use has errors on the order of meters, which, as mentioned, is insufficient for high-precision surveying. RTK corrects these errors in real time via relative positioning to a ground-based reference station, improving accuracy to the centimeter level.

RTK positioning usually requires a high-precision GNSS receiver and exchange of correction information via radio or network, but recently this technology has been miniaturized and made lower-cost, appearing as devices that can be linked with smartphones. In Japan, by using CLAS (a centimeter-level augmentation service) provided by the Quasi-Zenith Satellite System (QZSS, "Michibiki"), RTK-equivalent positioning is possible nationwide without dedicated radio stations. Integrating such advanced technologies into a smartphone enables survey-grade positional accuracy in the palm of your hand.

Domestic LRTK turns iPhone into a surveying instrument

The result is the smartphone-mounted RTK-GNSS receiver called LRTK. LRTK is a domestically developed device in Japan that can be integrated with iPhone and iPad. Although pocket-sized—weighing about 125 g and roughly 13 mm thick—it contains an antenna and battery and is designed to operate standalone. By attaching it to an iPhone via a dedicated smartphone case and connecting wirelessly via Bluetooth, the smartphone instantly becomes a surveying instrument equipped with a high-precision GNSS antenna.

LRTK was developed by Refyxia Inc., a startup spun out of Tokyo Institute of Technology. The company has produced a series of high-precision positioning devices for smartphone use with the aim of changing conventional surveying practices. Designed as a practical product anyone can use based on field feedback, LRTK has already attracted attention from many surveying and construction professionals. As noted earlier, while initiatives to use smartphones for high-precision positioning have started overseas, cases that integrate this with 3D scanning functionality like LRTK are still not common. The domestically produced LRTK is an advanced solution even by global standards.

LRTK provides high-precision position information to the smartphone in real time. The secret is its RTK-capable GNSS receiver. LRTK can receive CLAS signals from Japan’s Quasi-Zenith Satellite System “Michibiki,” enabling centimeter-level positioning even in mountainous areas outside of mobile network coverage. Of course, where cellular networks are available, it can also receive correction information via networked RTK (Ntrip). In other words, with an iPhone equipped with LRTK, you can measure your current position to within a few centimeters in both urban and remote locations.

Centimeter-level point cloud measurement enabled by iPhone 3D scanning + LRTK

Now let’s look at the core application in 3D scanning. When LRTK is used in conjunction with iPhone 3D scanning, it is possible to attach high-precision absolute coordinates to each point in the acquired point cloud data. Generating a “coordinate-equipped point cloud,” which is impossible with a smartphone alone, becomes achievable without special effort.

Moreover, because LRTK continuously measures its own position at the centimeter level, it greatly reduces the point cloud distortions and drift that commonly occur during scanning. For example, even when walking and scanning a wide area that includes the ground, LRTK’s position corrections prevent the point cloud from tilting or shrinking mid-scan. As a result, you obtain consistent 3D data with high accuracy from start to finish.

With LRTK-assisted iPhone point cloud scanning, you can acquire point clouds aligned to roughly centimeter-level accuracy. The acquired point cloud data can be output in formats that conform to official standards such as those for construction work acceptance management, so they can be used as formal surveying deliverables. The LRTK app can also convert and output acquired point cloud data into standard coordinate systems such as the Japanese plane rectangular coordinate system or geoid heights, facilitating smooth integration with other survey results and CAD data. You can overlay on-site point clouds directly onto design drawings for checks or use them for numerical earthwork volume calculations—clear practical advantages.

Usage is simple. Hold an iPhone with the LRTK device attached and walk around the area you want to scan. As you move while pointing the camera and LiDAR, surrounding point clouds are generated automatically and high-precision coordinates are attached simultaneously. No special calibration work or complicated settings are required—intuitive operation completes the task. Even large sites can be scanned in a matter of minutes, and you can check the point cloud on the smartphone immediately after acquisition. You can quickly measure distances between arbitrary points or display cross-sections on the spot, allowing real-time situational awareness.

In addition, by using the iPhone’s camera functions, targets outside the effective range of LiDAR can also be captured as point clouds. With LRTK-assisted scanning, structural objects as far as 50–60 m away can be captured as 3D point clouds using just the iPhone. Even high bridge girders or distant slopes can be recorded in detailed three-dimensional data from the ground.

Practical uses of iPhone point cloud measurement on site

High-precision point cloud measurement using iPhone and LRTK is useful in a variety of on-site scenarios. Below are representative use cases.

• As-built surveying: Obtain detailed 3D data of site terrain and structures before construction in a short time. Tasks that traditionally required measuring many points with a total station or setting up a terrestrial laser scanner for extended periods can be completed simply by walking with an iPhone. It is powerful for survey preparation and rapid terrain assessment.

• Visualizing design intent: Overlay a design-stage 3D model onto the existing point cloud to preview the completed appearance before construction. High-precision AR display allows intuitive on-site simulation of whether structures can be positioned according to design. This facilitates shared understanding of the finished form between client and contractor, helping prevent construction errors and smoothing change negotiations.

• Acceptance management and quality checks: Scan shapes during or after construction and compare them with design data (3D models or drawings). By color-coding differences between point cloud data and the design model, you can instantly see surplus or deficit in earthworks or finish discrepancies. Functions such as performing volume calculations on the LRTK cloud to compute required earthwork quantities can also be utilized.

• Infrastructure inspection and records: Useful for inspecting bridges, tunnels, road slopes, and other infrastructure. LiDAR scanning records shapes while photos of concerning cracks or damage can be taken with the iPhone and saved with precise position tags. You can later identify exactly where a photo was taken on the point cloud, making deterioration management and report preparation easier.

• Stakeout and layout tasks: Use coordinates obtained with LRTK to support on-site layout work. For example, stake positions or structure installation points can be guided via AR display on the smartphone screen. Tasks that previously involved cross-referencing drawings with surveying equipment can be performed intuitively and quickly with LRTK, allowing accurate point identification even by less experienced personnel.

• Information gathering during disasters: iPhone + LRTK is powerful even at disaster sites like earthquakes or landslides. Because CLAS-based positioning is possible even when cellular communications are down, photos taken at disaster sites can be recorded with precise location information, and collapsed terrain can be scanned to aid recovery planning. In the 2023 Noto Peninsula earthquake, a local civil engineer who happened to carry an LRTK successfully recorded damage at a site outside of mobile coverage as geotagged photos. LRTK’s ability to record site conditions without relying on communications infrastructure makes it highly valuable for disaster response. Its small, portable size also makes it effective for workers to carry individually for situation awareness in emergencies.

Comparison with conventional technologies and advantages

Let’s summarize the benefits that iPhone + LRTK point cloud measurement brings to job sites, compared with conventional surveying methods.

• Ease and speed: Anyone can perform measurements using a smartphone without special training. Walk the site and point clouds are obtained immediately; data processing is automated, so results can be available the same day. This is overwhelmingly faster than the traditional process of preparing equipment by a dedicated surveying team and spending time on data processing.

• Cost efficiency: Conventional high-precision surveying equipment (high-end GPS receivers, 3D laser scanners, etc.) requires significant acquisition and maintenance costs. LRTK leverages smartphones to reduce device costs and can be introduced relatively inexpensively. With one device per person, it’s realistic for all field staff to perform surveying and recording simultaneously. Regular calibration or special maintenance is unnecessary, and operation with familiar smartphones reduces ongoing costs.

• Portability: The compact, pocket-sized setup eliminates the need for heavy tripods or stationary equipment. It is easy to carry into remote or high-elevation areas where transporting equipment is difficult. Measurements can be made safely with one hand on rough slopes, greatly reducing worker burden. There is no need to transport large equipment by vehicle, and handling in confined sites or at height is simple.

• Multifunctionality: With LRTK and an iPhone, you can perform point surveying (single-point positioning), 3D scanning, photo documentation, AR visualization, and more with a single device. Traditionally, each function required separate equipment (GPS surveying instruments, laser scanners, digital cameras, AR gear), but all of that can now be consolidated into one smartphone.

• Real-time sharing: Measurement data can be uploaded to the cloud from the smartphone immediately. Office personnel can share results in real time and provide feedback sequentially. This reduces communication loss between the field and office and minimizes rework or additional surveying. Recipients can view point clouds from a web browser without special software, enabling information sharing regardless of PC performance.

• Positioning regardless of location: Support for satellite augmentation (CLAS) means positioning accuracy does not degrade in areas without cellular reception. Whereas network-based GNSS surveying becomes difficult outside coverage, LRTK can be used stably in mountainous areas and remote islands. Because positioning is possible even when networks are cut during disasters, it also offers advantages in risk management.

Conclusion: on-site transformation through simple surveying with LRTK

This new surveying style, combining the convenience of the iPhone with the precision of LRTK, is set to bring innovation to job sites. LRTK-enabled simple surveying lowers the barrier so that tasks once dependent on specialized technicians can be performed by anyone, dramatically reducing the threshold for surveying. A time is near when, without relying on veteran know-how, accurate digital records of site conditions can be made with a single smartphone.

For example, it is becoming realistic for every site staff member to attach an LRTK to their own smartphone and perform surveying or recording whenever needed. There is no longer a need to wait for a specialized team to arrive or to prepare large-scale equipment. You can collect and share high-precision data on the spot whenever the opportunity arises.

These next-generation measurement methods are already being trialed on some sites, and their efficiency and accuracy are being demonstrated. The conventional wisdom of surveying is being rewritten. Realizing centimeter-level point cloud measurement with an iPhone means that on-site DX (digital transformation) will accelerate further. Not only will surveying operations become more efficient, but construction management and maintenance practices will also evolve. Will you join in adopting this new world of simple surveying opened up by LRTK and help shape the future of on-site work?