Revolutionize the Jobsite with AR Construction Navigation!【iPhone RTK Device】×Smartphone Surveying

Table of Contents

• Introduction: Background of interest in iPhone RTK devices and AR construction navigation

• Basics of RTK positioning and the shift toward smartphone RTK

• Structure and accuracy advantages of iPhone RTK devices

• What is AR construction navigation? (construction navigation, stakeout/pile-driving support, overlaying drawings)

• On-site use cases (stakeout/pile driving, point cloud scanning, as-built management, disaster response)

• What smartphone surveying enables (single-person surveying, reduced cabling, cloud synchronization)

• Comparison with other methods (differences from total stations and conventional RTK equipment)

• Encouraging adoption of simplified surveying with LRTK and recommendations for implementation

• FAQ (frequently asked questions about iPhone RTK devices, AR construction navigation, and smartphone surveying)

Introduction: Background of Interest in iPhone RTK Devices and AR Construction Navigation

Digital transformation (DX) aimed at improving operational efficiency and productivity is rapidly advancing in the construction and civil engineering industries. One technology attracting particular attention is a new surveying style that combines AR (augmented reality) and RTK-GNSS. Traditionally, achieving high-precision positioning and setting-out required large surveying instruments such as total stations and the skills of veteran technicians. However, recently it has become possible—simply by combining a smartphone such as an iPhone with a compact RTK device—to realize centimeter-level positioning and AR-based visualization. For site managers and surveyors, the fusion of iPhone RTK terminals and AR technology is becoming a groundbreaking on-site tool that is set to significantly transform surveying operations and construction management practices.

In this article, we first explain the basics of centimeter-level positioning using the RTK method. Next, we introduce how to incorporate this into smartphones and what becomes possible on-site when combined with AR (augmented reality). Furthermore, we describe the structure of RTK-capable devices that attach to the iPhone (iPhone RTK terminal), the mechanism of high-precision positioning, and their strengths. We then examine what AR-based construction navigation (AR construction navigation) is, looking at its specific functions and benefits. We also touch on advantages unique to smartphone surveying, such as labor savings and cloud integration, and compare these with conventional surveying methods (total stations and traditional RTK equipment). Finally, we propose applying an easy-to-deploy LRTK system for simple surveying and summarize the benefits of introducing it to your site. At the end of the article, an FAQ answers common questions about iPhone RTK terminals, AR construction navigation, and smartphone surveying for your reference.

Basics of RTK Positioning and the Shift to Smartphones

First, let's cover the basics of high-precision positioning using the RTK method. RTK (Real Time Kinematic) is a technology that corrects errors in satellite-based positioning (GNSS) in real time, dramatically improving positional accuracy. Typically, the positional information obtained by common GPS receivers, such as those in smartphones, has errors on the order of several meters. That is acceptable for indicating your current location in a map app, but determining the exact position and elevation of structures on construction sites, or verifying deviations in as-built shape (the shape after construction), requires accuracy within a few centimeters. RTK positioning was developed to meet these needs.

In RTK, two receivers are used simultaneously: a base station (a fixed GNSS receiver with a known position) and a rover (the receiver located at the point to be measured). The system compares the satellite signals received by both receivers and cancels common error sources to correct the rover’s position to centimeter-level accuracy. Simply put, it is a method of “measuring with two receivers at once to cancel out errors.” This real-time differential correction enables the rover (the field-side receiver) to obtain its position in real time and with high precision.

Traditionally, to perform RTK positioning it was necessary to set up a base station at a known point yourself and exchange correction information with the rover via radio communication. However, a network RTK that allows use of data from the electronic reference points (GNSS reference network) installed nationwide by the Geospatial Information Authority of Japan, as well as private correction information services, over the Internet has become widespread. Even when using a smartphone, by using this network RTK (e.g., the Ntrip protocol) you can receive correction data in real time without dedicated equipment. In Japan, the Quasi-Zenith Satellite “Michibiki” also provides the Centimeter-Level Augmentation Service (CLAS), and compatible receivers can receive correction signals directly from the satellite even in mountainous areas outside cellular coverage. These developments have made centimeter-level positioning with RTK more readily accessible.

With RTK-GNSS positioning achieved in this way, errors that were about 5–10 m in standalone positioning are reduced to about one-hundredth, bringing them within a few centimeters. In practice, when using network RTK, there are reports of horizontal-position errors of about 3–4 cm. This dramatic increase in accuracy allows initial layout marking and pile-driving operations on construction sites to be performed accurately, preventing rework and corrections in later stages. Surveying work itself is also streamlined, and in situations where a total station previously required two people to operate, a single person can now simply walk with a GNSS receiver and measure many points in a short time. In other words, RTK positioning delivers significant benefits to the construction and surveying sectors in terms of both quality improvement and labor saving.

And in recent years, a trend of using RTK positioning on smartphones has emerged. With smartphones themselves becoming more capable (the inclusion of high-sensitivity dual-frequency GNSS receivers and improvements in computing power and sensor performance), and with the advent of compact RTK devices and services, an era is approaching in which smartphones can be used directly as high-precision positioning instruments. In particular, the iPhone, equipped with high-accuracy GNSS and excellent camera and LiDAR sensors, is a platform well suited to this RTK technology. In the next chapter, we will take a closer look at the structure of RTK positioning terminals (smartphone surveying devices) using the iPhone and at the mechanisms and strengths of their high-precision positioning.

Structure and Accuracy Strengths of the iPhone RTK Terminal

So, how exactly does an iPhone RTK device that enables centimeter-level positioning on a smartphone work? A representative solution that has recently emerged is a system in which an ultra-compact RTK-GNSS receiver is attached to a handheld iPhone. For example, Refixia's "LRTK Phone" is pocket-sized, measuring about 1 cm thick and weighing just 125 g, yet includes a built-in battery and functions as an all-in-one surveying device. It is used in combination with a compact antenna module that snaps onto a dedicated phone case with one touch and a surveying smartphone app (the LRTK app). The external LRTK device connects to the iPhone via the Lightning connector or Bluetooth, providing the smartphone with high-precision positioning information.

This iPhone RTK terminal primarily uses the aforementioned network RTK (Ntrip-compatible) positioning method. Wherever a smartphone can connect to the Internet, it can obtain correction data from the Geospatial Information Authority of Japan’s Continuously Operating Reference Station network or from commercial RTK services to enable real-time positioning. In addition, to support use in mountainous areas outside of communication coverage, it is also equipped to directly receive the QZSS (Michibiki) CLAS signal (L6 band) to obtain augmentation information, allowing it to measure the current position with centimeter-level accuracy both online and offline. In actual tests, this high accuracy has been confirmed, showing only a difference of a few millimeters compared to class-1 surveying GNSS equipment, providing sufficient reliability for field surveying.

The iPhone’s hardware is also a strength of this system. The iPhone is equipped with a high-performance camera, LiDAR scanner, and various gyroscope and accelerometer sensors, and by fusing the precise position coordinates obtained via LRTK with the smartphone’s orientation and distance data, it can deliver the same diverse surveying and AR functions introduced above on a single device. On the dedicated app, specialized operations such as coordinate system transformations (conversion from the World Geodetic System to plane rectangular coordinates and localization) and averaging of positioning data can be performed with one tap, so it’s designed to be easy to use even without deep surveying knowledge. Measured results can be uploaded to the cloud with the push of a button, enabling real-time sharing such as immediately checking measurement data and point cloud models from an office PC. No heavy equipment or complex cabling is required, making it a truly innovative device aimed at "measuring an entire site with just a smartphone."

What is AR Construction Navigation? (Construction navigation · Pile-driving support · Overlaying drawings)

AR施工ナビ is a construction navigation feature realized by combining RTK high-precision positioning with AR (augmented reality) technology. It overlays digital guide information and design data onto the actual site view seen through a smartphone screen, intuitively supporting work.

For example, when guiding workers toward pre-registered pile-driving positions or surveying points, you can display AR arrows and lines on the smartphone screen to indicate the direction to proceed. When you approach the specified coordinates, holding up the smartphone will cause a target marker (a landmark) to appear overlaid on the camera feed, accurately indicating the spot. Traditionally, it was necessary to determine positions by comparing drawings and surveying instruments, but with an AR construction navigation system, a mark on the screen indicating "this is the design position" is visualized, allowing workers to reach the destination without hesitation and complete pile-driving or layout-marking tasks simply by marking the spot. Even in locations where a physical pile cannot be installed (on bedrock or concrete, or on an extension outside the site), you can substitute by placing a virtual pile or pin in AR to indicate the position. Such pile-driving support enables positioning tasks that previously required multiple people to verify each other to be carried out accurately by a single person.

Furthermore, AR Construction Navi also enables overlay display of drawings and design data. For example, if you load pre-prepared design drawings (CAD data or 3D models) into your smartphone, you can overlay that data onto the actual scene through the camera on site. You can easily AR-display design lines on the ground to check boundary lines and finished heights, or project a predicted 3D model of a structure onto the site to share the expected finished appearance. Moreover, because it is based on high-precision RTK positioning information, the digital model and real-world positions align exactly, and even if a user walks around and views it from various angles, the model remains fixed to the ground without shifting.

By using the AR construction navigation in this way, information on the drawings can be directly visualized on site, greatly reducing the effort of interpreting paper drawings or re-measuring with a tape measure. It also proves powerful for sharing and communicating with clients and on-site staff, and is expected to help prevent mistakes caused by misunderstandings. The display misalignment that inevitably occurred with AR alone is resolved by accurate self-positioning using RTK, making it a practical navigation tool that can be used on site.

On-site Use Cases (Piling · Point Cloud Scanning · As-built Management · Disaster Response)

The new surveying method that combines smartphones and RTK can be applied to a variety of uses on real construction sites. Here are some representative scenarios.

• Pile-driving and layout (staking) work: Smartphone surveying is useful for marking reference points and pile-driving positions based on blueprints. If boundary points and installation coordinates for structures are preloaded to the smartphone via the cloud, the device will navigate you to those points on site. When you get close, switch to detailed mode and, relying on AR targets displayed in the camera view, you can pinpoint positions. By simply marking the spot, pile-driving and staking/layout are completed, greatly reducing the need to remeasure repeatedly or have multiple people verify. Accurate positioning can be carried out by a single person, dramatically improving work efficiency and precision.

• As-built management (single-point surveying): An iPhone fitted with an LRTK device can be touched to the point you want to measure—like the tip of a survey pole—and with a push of a button instantly record that point’s latitude, longitude, and elevation. Measurement time, satellite reception status, and other information are also recorded automatically, so it truly functions as an electronic field notebook. The acquired coordinate data is saved to the cloud and can immediately be used on office PCs for comparison and verification against design values and for calculating as-built quantities. There is no need to jot notes in a paper field book and bring them back; because data processing can be completed on-site, the as-built management cycle is dramatically shortened. In situations that require point-by-point measurements—such as checking pavement thickness or embankment heights—the major benefit is that anyone can easily produce a large number of accurate survey points.

• 3D point cloud scanning (as-built survey): By combining the iPhone’s built-in LiDAR scanner with RTK, on-site 3D scanning can be performed easily. With LiDAR measurement using only a smartphone, there was an issue where point cloud data would gradually become distorted due to self-position estimation errors during scanning. However, by performing walking scans while continuously correcting the device’s position with RTK, every acquired point in the point cloud is assigned the correct global coordinates (public coordinates), allowing the creation of high-precision 3D point cloud models with minimal distortion. With a pocket-sized smartphone alone, you can walk around and measure extensive terrain and structures, obtaining necessary distances and areas on-site, and even performing volume calculations for embankments and excavations. If you upload the point cloud data to the cloud immediately after acquisition, you can calculate volume differences and create cross-sections in the browser without installing software. For example, you can scan the existing terrain before construction and overlay that point cloud with the design model to instantly calculate earthwork volume differences on-site. Point cloud data can also be downloaded and imported into CAD software, which is useful for preparing downstream documentation.

• Disaster Response and Emergency Surveying: Smartphone surveying also contributes to rapid situational assessment at disaster sites. Immediately after a disaster, it is essential to record and share current conditions as quickly as possible, but there are many situations where it is not feasible to bring in heavy machinery or surveying equipment. In such cases, a smartphone surveying device that fits in your pocket proves powerful. By walking through the affected area and scanning the surroundings with a smartphone, you can measure the volume of collapsed soil and the extent of damage on the spot. In addition, high-precision geo-tagged photos taken with a smartphone become valuable resources for planning recovery work and for later verification. Even when communication infrastructure has been cut off, receiving Michibiki satellite augmentation signals directly allows positioning, so highly reliable surveying even in offline environments is possible. Data collected on site can be immediately shared to the cloud, enabling stakeholders to share information instantly and coordinate responses, thereby improving the speed and accuracy of disaster response.

What Only Smartphone Surveying Can Do (Single-Person Surveying · Reduced Cabling · Cloud Synchronization)

Utilizing smartphones as surveying instruments brings about numerous advantages that could not be obtained with conventional equipment. Among these, we highlight the points that can be particularly experienced on site.

• Survey work that can be completed by one person: With smartphone surveying, the need to carry heavy tripods and surveying prisms and to work in two-person teams is eliminated. Because you can acquire measurement points one after another simply by walking around the site with the device in one hand, the scope of tasks that can be completed by a single person expands even at sites facing labor shortages. In particular, tasks that previously required multiple people to set up, such as pile driving and as-built measurements, can be handled with a smartphone in hand, leading to reduced labor costs and shorter work times.

• Simple, cable-free equipment: Because it’s a simple setup of a smartphone plus a compact GNSS receiver, there’s no need to install equipment or run cables on site. With less gear to carry and easier mobility, it delivers agility in situations such as surveying at heights or in confined spaces, or managing multiple remote sites. Also, common problems with dedicated equipment—like “battery dying on site and needing replacement” or “cable breakage interrupting a survey”—are less likely to occur, and as long as the smartphone is working you can carry on surveying with ease.

• Real-time cloud synchronization: Smartphone surveying takes advantage of being constantly connected to the network, making data cloud synchronization easy. By uploading position data, point cloud models, photos, and other items measured on-site to the cloud, you can instantly share the data with staff in the office and other stakeholders. This enables real-time verification of as-built data and comparison with design drawings, and allows immediate discussion of countermeasures for problems that arise on-site, so that the speed of information transfer is dramatically improved. Because data is automatically backed up, you don’t have to worry about losing field notebooks or making mistakes when transcribing notes, allowing you to focus on surveying with peace of mind.

Comparison with Other Methods (Differences from Total Stations and Conventional RTK Equipment)

Both new smartphone surveying and conventional surveying instruments (total stations and existing RTK-GNSS surveying equipment) have their own advantages. Here we compare the main differences.

• Comparison with Total Station (TS): A total station is an optical surveying instrument that uses prisms and can measure distances and angles with millimeter-level accuracy, so it remains indispensable for precise installation of structures and laying out reference lines. However, TS requires ensuring line of sight and equipment setup, and its operation normally presumes work by two or more people—a surveyor and a target holder. On the other hand, smartphone + RTK surveying can obtain positions directly from satellites in open outdoor environments, so it is particularly effective on wide sites with few obstructions to the line of sight. As long as control points are known, tripod setup is unnecessary, and one person can move between measurement points quickly, providing high mobility. Because absolute coordinates can be obtained immediately, another advantage is the ability to continuously collect data over multiple days without day-to-day re-establishment errors. However, GNSS surveying cannot be used in environments where satellite signals do not reach, such as inside forests or buildings, so in those situations it is still necessary to use TS or levels. By choosing between TS and smartphone surveying according to the application, you can optimize overall work efficiency.

• Comparison with conventional RTK-GNSS equipment: Conventional RTK surveying units (GNSS rovers) were expensive gear with dedicated large antennas and controllers built into the receiver body. While dedicated terminals are rugged and offer high positioning accuracy, the devices tend to be heavy and often require specialized knowledge to operate. Smartphone RTK replaces some functions of those dedicated units with a compact device and an app, so it is attractive because you can achieve nearly the same accuracy while drastically reducing initial investment costs. Also, as a smartphone-specific advantage, it can simultaneously use multi-functional features beyond positioning—such as photography, point cloud scanning, and AR projection. For example, a workflow that previously measured coordinates with a conventional device and then separately recorded photos with a camera can be completed with a single smartphone, capturing photos with coordinates in one tap. Furthermore, in terms of cloud integration and UX (user experience), smartphone apps are intuitive and easy to update. On the other hand, because smartphones are not all-weather rugged hardware like dedicated units, measures such as placing the phone in a waterproof case or using a mobile battery are necessary for use in rain or during prolonged continuous operation. Even so, after accounting for these points, the ease and multifunctionality of smartphone surveying remain major advantages not found in conventional equipment.

Guiding and Encouraging the Adoption of Simplified Surveying with LRTK

As introduced above, the centimeter-level smartphone surveying made possible by the fusion of smartphone × RTK represents a new on-site workflow that enables anyone to easily perform tasks that previously depended on specialized equipment and skilled technicians. With the combination of an iPhone and compact RTK devices (such as LRTK), positioning, measurement, recording, and visualization can all be completed on a single device, accelerating the DX (digital transformation) of field operations.

It is truly "a surveying instrument in your pocket"—the smartphone surveying tool is poised to significantly rewrite the norms of surveying and construction management. Even without relying on expensive dedicated equipment or veteran workers, the era when anyone can perform surveying that achieves both accuracy and efficiency with a smartphone in hand is just around the corner. Don’t be bound by traditional methods; be sure to incorporate this next-generation surveying style on site. You will surely be surprised by its convenience and the reliability of its results.

By leveraging the smartphones and RTK providehigh-precision and intuitive surveying, you can dramatically improve on-site productivity and quality. Why not take such an innovative step at your workplace as well?

FAQ (Frequently Asked Questions about iPhone RTK Devices, AR Construction Navigation, and Smartphone Surveying)

Q: What is an iPhone RTK device? A: It is a surveying terminal that combines a compact, high-precision GNSS receiver (an RTK-capable GPS antenna) that attaches to and is used with a smartphone such as an iPhone, and a dedicated app that utilizes the positioning data. Using the smartphone’s communication functions, it receives correction information from a reference station and corrects GPS positioning—which alone can have errors of several meters—in real time to determine positions with accuracy of a few centimeters. The "iPhone RTK device" makes precision surveying, which formerly required large, fixed equipment, possible with a handheld smartphone.

Q: How accurate is RTK surveying using a smartphone? A: Depending on conditions, you can generally achieve ± a few centimeters horizontally and ± a few centimeters vertically. In open, flat environments with good visibility, it has been confirmed that positioning can be as accurate as dedicated surveying instruments (in some cases errors are confined to a few millimeters to the low-centimeter range). However, accuracy degrades in environments where satellite signals are disturbed—such as inside forests or in the canyons between high-rise buildings—so it is necessary to measure in locations with good positioning conditions when required, or to combine the smartphone with other surveying equipment.

Q: Is a base station or internet connection required to use it? A: You basically do not need to provide your own base station. Smartphone RTK acquires correction data over the internet from the Geospatial Information Authority of Japan’s Continuously Operating Reference Stations network and from private correction services (such as VRS), so as long as mobile data is available on site, you’re fine. Even if you’re out of coverage, a device that can directly receive the CLAS signal from the Quasi-Zenith Satellite Michibiki can obtain augmentation information from the satellite and achieve centimeter-level positioning. For that reason, surveying work can continue even in mountainous areas without network connectivity.

Q: What can you do with AR Construction Navi? A: With AR Construction Navi, you can perform tasks such as pile driving and as-built inspections with intuitive assistance via AR display. It navigates to specified coordinates using arrows and distance indicators on the smartphone screen, and when you reach the target point it projects a target marker onto the camera view to indicate the position. This allows you to locate pile-driving positions accurately without hesitation. It can also overlay design drawings and 3D models onto the site view, allowing you to share and confirm the expected finished image on the spot. For example, it can be used to compare the design model with the current conditions to detect construction deviations or to show the client the projected completion. In short, AR Construction Navi supports work by making drawing information visible on-site.

Q: Can it be used without specialized knowledge? A: Yes. The smartphone surveying system is designed so that field technicians can operate it intuitively. On the dedicated app, complex coordinate calculations and positioning data processing are automated, allowing anyone to use it with the push of a button. Because AR provides visual guidance, accurate positioning and measurements are possible even without surveying expertise. In fact, there are cases where young technicians have used smartphone surveying and become immediately effective on the job. With a short training session, even first-time users can become proficient in on-site operations in a short time.