Achieving centimeter-level point cloud measurement with iPhone 3D scanning! Japan-made LRTK changing the field

Table of Contents

• Easy 3D scanning starting with the iPhone

• Challenge: a smartphone alone lacks sufficient accuracy

• Improving positioning accuracy with RTK technology

• Japan-made LRTK turns the iPhone into a surveying instrument

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

• Practical use cases for iPhone point cloud measurement on site

• Comparison with conventional technologies and advantages

• Summary: the field changes with simple surveying using LRTK

The era when high-precision three-dimensional measurement can be done with a single smartphone has arrived. By combining the iPhone’s 3D scan capability with a domestically developed positioning technology called LRTK, anyone can easily acquire centimeter-level point cloud data that previously required expensive dedicated equipment. On-site measurement workflows are now on the verge of a major transformation.

Traditionally, precision surveying and 3D measurement were performed by skilled technicians using expensive instruments such as total stations or laser scanners. However, in recent years, digital transformation (DX) has swept through the construction industry, and on-site measurement methods are rapidly evolving. As promoted by the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative, efficiency improvements using ICT are being advanced, and easy 3D scanning with smartphones is expected to be a powerful solution for on-site DX. Now, the smartphone that everyone carries is about to become the star of surveying.

Easy 3D scanning starting with the iPhone

Recent iPhone and iPad Pro models are equipped with compact LiDAR (light-based ranging) scanners, making 3D scanning easy to perform. With dedicated apps, you can simply wave the device around a space or object to scan and record it as a 3D model or point cloud data. Tasks that once required specialized equipment or professional contractors—such as measuring the dimensions of a room or creating a 3D model of an object for AR display—can now be done with just a smartphone. The ability to handle three-dimensional data on a palm-sized device has attracted attention across a wide range of fields, from construction and design to entertainment.

Although efforts to use smartphones for high-precision positioning have begun overseas, cases that integrate 3D scanning functionality as comprehensively as LRTK are still rare. Japan-made LRTK can be considered an advanced solution even by global standards.

In fact, the App Store already hosts many 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 ease with which precise measurement and 3D data creation, once requiring specialized equipment, can now be done with a single smartphone is truly revolutionary.

*Note: point cloud scanning functions are available on iPhone and iPad Pro models equipped with LiDAR. For higher-precision measurement, using models with the latest sensors (for example: iPhone 15 Pro) is recommended.*

Challenge: a smartphone alone lacks sufficient accuracy

While iPhone 3D scanning is convenient, there are several accuracy-related challenges when attempting to use it directly for actual surveying purposes. First, point cloud data acquired by a smartphone alone is not assigned absolute coordinates. The generated 3D data remains in a local coordinate system, and its position on a map is unclear. For example, if you scan the terrain of a site, unless that point cloud is tied to real latitude/longitude or known control points, it becomes difficult to compare it with construction drawings or integrate it with other survey data.

Second, because the smartphone relies solely on its onboard sensors to track position, errors tend to accumulate when walking while scanning over large areas. Over time, the device’s self-position estimation can drift, and it is often pointed out that horizontal surfaces such as the ground can become distorted. When scanning a large area continuously, the point cloud may gradually shift and eventually represent a shape that differs from reality.

Thus, iPhone 3D scanning has limitations in terms of positioning accuracy in exchange for ease of use. 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 3D scanning with a smartphone?

Improving positioning accuracy with RTK technology

The key is RTK (Real Time Kinematic) technology, which corrects satellite positioning errors to obtain precise positions. The GPS-based positioning we commonly use typically has errors on the order of meters, which is insufficient for the high-precision surveying mentioned above. RTK corrects these errors in real time by relative positioning with 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 in recent years this technology has become smaller and less expensive, and devices that can cooperate with smartphones have appeared. In Japan, using the quasi-zenith satellite Michibiki’s CLAS (centimeter-level augmentation service) makes RTK-equivalent positioning possible nationwide without a dedicated radio station. By incorporating such advanced technology into a smartphone, you can achieve surveying-level positioning accuracy in the palm of your hand.

Japan-made LRTK turns the iPhone into a surveying instrument

This led to the development of LRTK, a smartphone-attached RTK-GNSS receiver. LRTK is a Japan-made device that can be used integrated with iPhone and iPad. Weighing about 125 g and with a thickness of about 13 mm (0.51 in), it is pocket-sized yet houses an antenna and battery and is designed to operate standalone. It attaches to the iPhone’s Lightning connector (or USB-C port) via a dedicated smartphone case and connects wirelessly via Bluetooth, transforming the smartphone into a surveying instrument equipped with a high-precision GNSS antenna.

LRTK was developed by Reflexia Inc., a startup spun out of Tokyo Institute of Technology. The company has been producing high-precision positioning devices usable with smartphones to change the way surveying is done. Designed as a practical product anyone can use by incorporating feedback from field users, LRTK is already attracting attention from many surveying and construction professionals. Although efforts to use smartphones for high-precision positioning are also beginning overseas, cases that integrate 3D scanning functionality as comprehensively as LRTK remain limited. Japan-made LRTK can be seen as an advanced solution even on a global scale.

LRTK provides high-precision position information to the smartphone in real time. Its secret is RTK-capable GNSS reception. LRTK can receive the Japanese quasi-zenith satellite system Michibiki’s CLAS signals, enabling centimeter-level positioning even in mountainous areas outside of regular communication coverage. Of course, where cellular networks are available, it can also receive correction data via network RTK using existing electronic reference station networks (Ntrip method). In other words, with an iPhone equipped with LRTK, you can measure your current position with centimeter-level accuracy whether you are in urban areas or deep in the mountains.

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

Now let’s look at the application to 3D scanning. When LRTK is used together with iPhone 3D scanning, each point in the acquired point cloud data can be assigned high-precision absolute coordinates. The generation of “coordinate-attached point clouds,” which was impossible with a smartphone alone, can be realized without special procedures.

Moreover, because LRTK continuously measures its position at the centimeter level, distortions and shifts commonly seen during scanning are greatly suppressed. For example, even when walking to scan a wide site including the ground, LRTK’s position corrections prevent the point cloud from tilting or shrinking midway. As a result, you obtain consistent 3D data with high accuracy from start to finish of the scan.

Using LRTK for iPhone point cloud scanning, you can acquire point clouds aligned with approximately centimeter-level accuracy (half-inch accuracy). The acquired point cloud data can be output in formats that comply with standards such as public works as-built management guidelines, so they can be used as official surveying results. In addition, the LRTK app can convert and output the acquired point cloud data into standard coordinate systems such as Japan’s plane rectangular coordinate system and geoid heights, making integration with other survey results and CAD data smooth. Being able to overlay measured point clouds directly onto design drawings for checks or use them for numerical earthwork calculations is a major advantage.

The usage is simple. Hold an iPhone fitted with the LRTK device and walk around the area you want to scan. Moving while pointing the camera and LiDAR automatically generates surrounding point clouds while high-precision coordinates are simultaneously attached. No special calibration work or difficult settings are required—intuitive operation completes the task. Even on large sites, scanning can be finished in a few minutes, and you can immediately check the point cloud on the smartphone. You can quickly measure the distance between any two points, display cross-sections, and perform other necessary on-site measurements, allowing you to grasp the situation in real time.

Additionally, by leveraging the iPhone’s camera functionality, objects that are beyond LiDAR’s effective range can also be captured as point clouds. With LRTK-enabled scanning, the iPhone alone can capture 3D point clouds of structures up to 50〜60 m (164.0〜196.9 ft) away. Whether it’s a bridge girder high above or a distant slope, detailed three-dimensional data can be obtained from the ground simply by pointing the smartphone.

Practical use cases for iPhone point cloud measurement on site

High-precision point cloud measurement with iPhone and LRTK is useful in many on-site scenarios. Representative use cases are introduced below.

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

• Visualization of design concepts: Overlay design-stage 3D models on the existing point cloud to confirm the finished appearance before construction. High-precision AR display allows intuitive on-site simulation of whether structures can be placed according to the design. This facilitates shared understanding of the finished product between contractors and clients, helping prevent construction errors and smoothing change negotiations.

• As-built management and quality checks: Scan the shape during or after construction and compare it with design data (3D models or drawings). By color-coding the differences between point cloud data and the design model, you can immediately grasp excesses or shortages in embankment/excavation and deviations in the finished work. Functions such as performing volume calculations on the LRTK cloud to compute required earthwork quantities can also be utilized.

• Infrastructure inspection and recordkeeping: Useful for inspecting structures such as bridges, tunnels, and road slopes. While recording shapes with LiDAR scans, you can photograph cracks or damaged areas with the iPhone and save those photos with precise position tags. Since you can accurately confirm “which location a photo corresponds to” later on the point cloud, managing deterioration and creating reporting materials become easy.

• Layout marking and staking: Use coordinates obtained with LRTK to support on-site layout work. For example, you can guide piling positions or installation points of structures by AR display on the smartphone screen. Layout work that previously required cross-checking drawings with surveying instruments can be done intuitively and quickly with LRTK, enabling even non-experts to identify points accurately.

• Information collection during disasters: iPhone + LRTK is powerful at disaster sites such as earthquakes and landslides. Because CLAS-based positioning is available even when cellular communication is down, you can photograph a disaster site with precise position data or scan collapsed terrain for restoration planning. In fact, during the 2023 Noto Peninsula earthquake, a local civil engineer who happened to carry LRTK successfully recorded damage at a site out of cellular coverage as photos with position information. LRTK’s ability to record site conditions without relying on communication infrastructure is highly valuable in disaster response. Its small, portable size makes it effective as a tool for individual workers to carry for situational awareness in emergencies.

Comparison with conventional technologies and advantages

Let’s summarize the benefits that iPhone + LRTK point cloud measurement brings to the field by comparing it with conventional surveying methods.

• Ease and speed: Anyone can perform measurements with smartphone operation without special training. Walking the site produces immediate point clouds, and automated data processing means results can be obtained the same day. This is overwhelmingly faster than the traditional process of a survey team preparing equipment and spending time on data processing.

• Cost efficiency: Conventional high-precision surveying equipment (high-end GPS receivers or 3D laser scanners) incurs significant purchase and maintenance costs. By leveraging smartphones, LRTK reduces equipment costs and is relatively inexpensive to introduce. With one device per person, it becomes realistic for all field staff to perform surveying and recording simultaneously. Also, regular calibration or special maintenance is unnecessary, and operation with a familiar smartphone offers long-term cost benefits.

• Portability: The compact, pocketable configuration eliminates the need for heavy tripods or fixed equipment. It is easy to carry even into remote mountain areas or high locations where transporting equipment is difficult. Measurements can be done safely with one hand on rough slopes, greatly reducing worker burden. There is no need to transport large equipment by vehicle, and handling in tight sites or at height is simple.

• Multifunctionality: With LRTK and an iPhone you can perform point surveying (single-point positioning), 3D scanning, photographic records, AR visualization, and more with one device. Previously, separate equipment (GPS survey instruments, laser scanners, digital cameras, AR devices) was required for each task, but now all can be consolidated into a single smartphone.

• Real-time sharing: Measurement data can be uploaded to the cloud from the smartphone immediately. Results can be shared in real time with staff in the office, allowing for prompt feedback. This reduces communication loss between the field and the office and minimizes rework or additional surveying. Recipients can view point clouds in 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 where cellular signals do not reach. Traditional network-type GNSS surveying struggled in areas outside network coverage, but LRTK can be used stably in mountainous regions and remote islands. Because positioning is possible even when networks are disrupted by disasters, it also offers advantages in risk management.

Summary: the field changes with simple surveying using LRTK

This new surveying style that combines the iPhone’s ease of use with LRTK’s precision is poised to bring innovation to the field. LRTK-enabled simple surveying lowers the barrier to measurement tasks that previously required specialist technicians, allowing anyone to perform them and dramatically reducing the hurdles for surveying. A time is near when you can accurately record site conditions digitally with just a smartphone, without relying on veteran know-how.

For example, the concept of every field worker carrying an LRTK-equipped smartphone and performing surveying and recording as needed is becoming realistic. There is no longer a need to wait for a specialist team to arrive or to prepare massive equipment for surveying. You can collect and share high-precision data on the spot whenever the need arises.

Such next-generation measurement methods are already being trialed at some sites, and their efficiency and accuracy are being demonstrated. The conventions of surveying are being rewritten. The ability to achieve centimeter-precision point cloud measurement with an iPhone means 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. Would you like to adopt this new world of simple surveying pioneered by LRTK and help shape the future of on-site work?