Achieving One-Person Construction with iPhone RTK Surveying: Improving On-Site Productivity by Introducing LRTK

On-site surveying and construction management face daily challenges such as "insufficient manpower" and "surveys taking too long." This article spotlights iPhone RTK surveying, which is attracting attention as a solution. The combination of smartphones and RTK technology enables even a single person to carry out highly accurate surveying and provide construction support. As the title indicates, this article explains in detail the points by which introducing iPhone RTK surveying can realize single-person construction and lead to improved productivity.

Table of Contents

• Challenges in on-site surveying and construction

• What is iPhone RTK surveying?

• “One-person construction” enabled by iPhone RTK surveying

• Examples of using iPhone RTK surveying on site - High-precision as-built surveying and rapid as-built management - 3D measurement and earthwork volume calculation via point cloud scanning - Layout marking using coordinate guidance and AR - Streamlining photo documentation and inspection tasks

• Key benefits of implementing LRTK

• Summary: The innovations iPhone RTK surveying brings to the job site

• FAQ

Challenges in on-site surveying and construction

At construction and surveying sites, accurate surveying and prompt construction management are essential for ensuring quality and safety. However, the following issues have been pointed out at small- and medium-sized sites.

• Labor shortages and securing specialized technicians: Surveying requires surveyors with advanced skills and teams of multiple people, but small and medium-sized construction companies in regional areas face labor shortages and an aging workforce, making it difficult to secure experienced personnel. As a result, it is not uncommon to have to hire specialist contractors for each surveying task or to struggle with personnel scheduling.

• Cost and unwieldiness of conventional surveying equipment: Conventional surveying equipment such as total stations and high-performance GNSS receivers is expensive and may require investments on the order of several million yen. The equipment itself is heavy, and including accessories such as tripods, poles, batteries, and dedicated controllers makes transportation and on-site setup time-consuming. In addition, initial configuration and the time for positioning to stabilize can take time, sometimes requiring waiting several minutes before surveying can begin.

• Inefficiencies in surveying operations: When limited surveying equipment is shared within a team, “waiting for surveying” time tends to occur. For example, other work may be halted to wait for turn to use a single device, or construction cannot proceed until the surveyor arrives. Also, traditionally survey results were recorded in paper field notebooks and had to be taken back to the office for drafting and data conversion, causing a time lag in information sharing between the field and the office.

• Safety and workload issues: Traditional surveying is typically performed by two-person teams (for example, one person holds the staff while the other operates the instrument), and work on unstable ground or at heights imposes heavy labor burdens and carries safety risks. Carrying heavy equipment itself becomes a burden on workers, increasing the risk of heatstroke and accidents.

Because of the issues described above, there is a growing demand to perform easy, high-precision surveying with a small team. This led to the emergence of a new surveying technology that leverages smartphones such as the iPhone: "iPhone RTK surveying."

What is iPhone RTK surveying?

iPhone RTK surveying is a surveying method that achieves centimeter-level positioning accuracy by combining high-precision GNSS positioning using the RTK method with a smartphone (particularly the iPhone). First, to briefly explain RTK (Real Time Kinematic): it is a technique in which a reference station (fixed station) and a rover simultaneously receive signals from GNSS satellites, and the error information obtained at the reference station is applied to the rover in real time, allowing errors of several meters typical of ordinary GPS to be reduced to the order of a few centimeters. This RTK positioning enables determining positions with accuracy comparable to conventional surveying instruments.

Positioning using an iPhone equipped with an LRTK device. A pocket-sized GNSS receiver integrated with the smartphone enables high-precision positioning anytime, anywhere. It can be easily attached and detached using a dedicated smartphone attachment, and because it operates cable-free via a Bluetooth connection, you can start surveying immediately when needed.

Traditionally, RTK surveying required large, dedicated equipment, but the arrival of LRTK (an ultra-compact RTK-GNSS receiver for smartphones) has changed the situation dramatically. By attaching this device to an iPhone or iPad and launching a dedicated app, a smartphone instantly becomes a centimeter-level accuracy surveying instrument (half-inch accuracy). The LRTK device is extremely compact, weighing approximately 125 g and measuring about 13 mm (0.51 in) thick, and it has a built-in battery, so no complicated cable connections are required. It truly provides the convenience of completing surveying with just a single smartphone.

Furthermore, the latest iPhones are equipped with LiDAR sensors and high-performance cameras, and by combining these with RTK positioning, 3D scanning and AR (augmented reality) can also be utilized. In iPhone RTK surveying, overlaying virtual objects and guides onto the smartphone’s camera feed enables intuitive on-site navigation, layout-marking assistance, and more advanced photo documentation. In this way, iPhone RTK surveying features "affordable, lightweight, easy, fast", and is revolutionizing traditional surveying methods.

One-person construction made possible by iPhone RTK surveying

When high-precision positioning becomes easily achievable on a smartphone, the way field work is conducted changes dramatically. What is particularly notable is that the introduction of iPhone RTK surveying enables a single person to handle surveying and construction management. Let’s look at the main points to see specifically how “one-person construction” can be realized.

• Can perform as-built surveying and inspection alone: Traditionally, when conducting as-built control surveying, it was necessary to have a surveyor come to site or to work in pairs with an assistant. With iPhone RTK surveying, construction managers or workers can perform surveys with their own smartphones and measure the as-built of structures (shape and dimensions) on the spot. For example, thickness after concrete placement or the quantity of excavated soil can be measured and recorded immediately and with high accuracy by a single person.

• Can perform layout marking and position setting alone: Establishing control points and marking stake positions (layout marking) can be completed simply by following guides on the smartphone screen. Traditionally, a surveying team would transfer coordinates from design drawings to the site, but with iPhone RTK surveying the worker is guided to the coordinates of required points and can place marks or display AR stakes as references. In particular, using the LRTK app’s coordinate guidance function, it guides you to the target point with arrows and distance displays, allowing a single person to set out positions accurately without using a tape measure or range-finding tools.

• Real-time sharing enables on-the-spot decisions: Positioning data and photos can be uploaded to the cloud on site and shared in real time with staff in the office. This eliminates the time lag caused by “waiting for survey results before reviewing and issuing instructions.” Because one person can measure and share immediately, on-site decisions that require judgment can be handled quickly.

• Lightweight equipment for safety and labor savings: Working alone can seem demanding, but with iPhone RTK surveying the equipment consists only of a smartphone and a small antenna. There's no need to carry heavy tripods or long staffs, so you can move nimbly even on sites with poor footing. For high-elevation measurements, techniques to obtain coordinates of the targeted position safely from below (for example, first surveying at a control point and then moving under a bridge) can reduce dangerous high-altitude work. As a result, the workload is reduced and safety is improved.

In this way, introducing iPhone RTK surveying dramatically increases "what a single person can do". On sites struggling with labor shortages, it allows a small team to complete everything from surveying to recording, directly improving productivity. Now, let's look at some specific on-site use cases.

On-site Examples of iPhone RTK Surveying

This introduces representative use cases showing how iPhone RTK surveying can be useful in real-world fieldwork. It demonstrates its effectiveness across a wide range of situations, from surveying and construction management to infrastructure inspections.

High-precision as-built surveying and rapid as-built management

As-built management is the process of checking and recording whether the shapes and dimensions of completed structures or construction sites conform to the design. By using iPhone RTK surveying, site supervisors themselves can measure the coordinates and elevations of each point immediately after construction and verify the as-built conditions on the spot. For example, in road construction, by measuring the pavement thickness and slope immediately after installation, any defects can be repaired immediately. In addition, because measurement data are automatically converted and recorded into plane rectangular coordinates and elevation (geoid height), there is no need to handwrite them in a paper field notebook, preventing missed measurements and recording errors. Measurement results can be sent to the office via the cloud, allowing the creation of as-built drawings and reports to be carried out quickly.

3D Measurement and Earthwork Volume Calculation Using Point Cloud Scanning

By combining the iPhone’s built-in LiDAR scanner with RTK positioning, it is possible to easily acquire 3D point clouds on site. Traditionally, 3D topographic surveying and as-built measurements required using expensive 3D laser scanners or performing photogrammetric analysis after drone aerial surveys. However, with iPhone RTK surveying you can obtain point cloud data with coordinates using just a smartphone. Because LRTK assigns accurate world coordinates (global coordinates) to each point, it also reduces the point cloud distortions that often occur during scanning.

From the acquired point cloud data, you can instantly determine the distance between any two points and cross-sectional shapes, and even perform embankment and excavation soil volume calculation on-site. You can take a device out of your pocket, scan the surroundings, and calculate volume directly on the smartphone screen. Point cloud data can be uploaded to the cloud and viewed and shared in a web browser on a PC, so you can proceed with detailed examinations in the office even without specialized point cloud processing software at hand. It also offers the flexibility for one person to respond immediately to small-site needs like “I just want to measure a bit of soil volume.”

Layout marking using coordinate guidance and AR

iPhone RTK surveying is also highly effective for positioning and marking work on buildings and structures. Using the LRTK app’s Coordinate Guidance feature, your smartphone will navigate you to a preset target coordinate point. The screen displays an arrow showing the direction to the destination and the approximate straight-line distance, so you can reach the target simply by following them. As you get closer, the display shows "○ cm (○ in) remaining" for fine adjustments, so you can pinpoint the desired coordinate even without specialized knowledge.

Screen image of the LRTK app's coordinate guidance. When you select the target point, an arrow appears on the camera view and provides real-time guidance of direction and distance. This allows a single person to locate the target point on a large site without getting lost.

Using the AR feature makes layout marking work even more intuitive. While viewing the site through your smartphone screen, you can display virtual stakes (AR stakes) and markers at the design positions. For example, by showing a virtual stake through the smartphone at the spot "drive a stake here," you can visually indicate positions even in locations where you cannot mark the ground directly (such as hard concrete surfaces or restricted-access areas). Based on the positions shown by the AR stakes, you can also take flexible approaches, such as carrying out the actual stake driving later when it is safe.

Streamlining Photo Documentation and Inspection Tasks

iPhone RTK surveying provides new value for infrastructure inspections and construction record photography. When you take photos with the LRTK app, high-precision coordinates and orientation information are automatically attached to each photo. This makes it easy to manage photo locations on a map and to accurately revisit the same location later.

Even more revolutionary is fixed-point photography using AR navigation. Because the position and orientation data of previously taken photos are recorded, when you approach the same point during an inspection, a "guide arrow for capturing the same composition as last time" appears on your smartphone screen. By simply pointing your smartphone according to this blue AR arrow, anyone can take a photo from the same angle as before. For example, even when performing regular inspections of slope cracks, you no longer have the problem of "not knowing which angle the photo was taken from," and comparison of changes over time can be carried out accurately.

Captured photos can be managed in the cloud as time-series data, and you can view the photo locations and orientations, along with the photos and notes, on a map. This makes it possible to immediately retrieve records from inspections carried out several years ago and refer to them on site, helping to prevent omissions or oversights during inspections. This digital record management is truly an electronic medical record for infrastructure, and it can be implemented even by a single worker.

Main benefits of implementing LRTK

Finally, we will summarize the main benefits of introducing iPhone RTK surveying on site. By leveraging LRTK devices and apps, the following benefits can be expected.

• Dramatic improvement in work efficiency and productivity: The initial RTK positioning (FIX) time is short, and you can start surveying in just a few seconds to several tens of seconds after turning on the power. Because you can measure immediately when the need arises, construction stoppages due to "waiting for surveying" are reduced, shortening the overall schedule. Since each person can carry one device at all times, the ability to take measurements immediately when needed directly translates into improved on-site productivity.

• Improvement in accuracy and quality: Using LRTK, you can stably achieve positioning accuracy of about 1–2 cm (0.4–0.8 in). Because this accuracy can be attained even by non-expert surveyors, high-precision data can be obtained regardless of who performs the measurement. Furthermore, by using the app’s averaging function, accuracy can in some cases be improved to errors of a few millimeters (a few 0.1 in), which helps with high-precision as-built control and quality management. As surveying accuracy increases, the reliability of as-built documentation and quantity calculations also improves, which in turn leads to overall enhancement of construction quality.

• Labor reduction and response to workforce shortages: Smartphone RTK is inexpensive and easy to introduce, so small and medium-sized enterprises that previously outsourced surveying each time can now handle surveying in-house. Without having to arrange specialized surveying technicians for every job, site staff themselves can perform surveying and recording, helping to resolve personnel shortages. Additionally, tasks that previously required two people can be done by one, yielding reduced labor costs and simplified personnel coordination.

• Cost reduction and return on investment: Smartphone surveying devices like LRTK are dramatically less expensive than traditional high-cost surveying equipment. Without purchasing GNSS receivers or 3D scanners that cost several million yen, you can use almost equivalent functions at an affordable price. There is no need to share one unit among a team, and even if you equip “one device per person”, the cost burden is low, so there is no waiting time or queue for equipment. It is a solution with high ROI in both equipment cost reduction and operational efficiency improvement.

• Improved safety and reduced work burden: Small, lightweight equipment reduces the physical burden of surveying work and lowers the risk of injuries or accidents from transporting heavy machinery. By utilizing AR technology, inspections of high places and hazardous areas can be carried out remotely, allowing necessary data to be obtained while ensuring worker safety. The introduction of such construction DX tools also offers significant benefits for labor safety.

Summary: How iPhone RTK Surveying Is Transforming the Field

iPhone RTK surveying is a technology that has become a game changer for regional small and medium-sized construction contractors and surveying firms. With high-precision surveying now possible with a single smartphone, tasks that previously relied on multiple people or specialists can be carried out by anyone on site. In an industry facing labor shortages and calls for workstyle reform, iPhone RTK surveying is precisely a solution that drives on-site DX (digital transformation).

By introducing an LRTK device, a single operator can handle a wide range of tasks—surveying, as-built management, inspections, and setting-out—and even share data in real time. As a result, on-site productivity and decision-making speed are dramatically improved, and quality and safety are ensured. This initiative also aligns with the Ministry of Land, Infrastructure, Transport and Tourism's *i-Construction* program, and its adoption is expected to accelerate going forward. Take this opportunity to introduce iPhone RTK surveying on site and achieve high-efficiency, high-quality work even with a small crew.

FAQ

Q: How accurate is iPhone RTK surveying? A: In iPhone RTK surveying, using the RTK method, positional accuracy is generally within several centimeters (several in) both horizontally and vertically. When using an LRTK device, standalone positioning is on the order of 1–2 cm (0.4–0.8 in), and under favorable conditions even higher accuracy (less than 1 cm (less than 0.4 in)) is possible. This is orders of magnitude more accurate than conventional GPS positioning (errors of several meters (several ft)), yielding survey results comparable to traditional instruments such as total stations.

Q: What do I need to start iPhone RTK surveying? A: Basically, you need an iPhone or iPad device and an RTK-capable external GNSS receiver (for example, an LRTK device). You also need a way to receive correction data for high-precision positioning, such as access to a network RTK service (e.g., connection to a reference-station network over the Internet) or, if you are in Japan, settings to use the Quasi-Zenith Satellite "Michibiki"'s centimeter-level augmentation service (CLAS) (cm level accuracy (half-inch accuracy)). The LRTK app makes these settings easy to configure.

Q: Can it be used in mountainous areas or sites outside of communication coverage? A: Yes, iPhone RTK surveying can be used in locations without a communications environment. LRTK devices support Japan’s satellite positioning augmentation service CLAS, and even in mountainous areas or disaster sites where mobile signals do not reach, they can receive correction signals directly from satellites and achieve centimeter-level positioning. In fact, there are reports of LRTK being used at disaster sites immediately after an earthquake when communication infrastructure was severed, allowing the positions and conditions of structures to be accurately recorded and shared.

Q: Can it be used without specialized surveying knowledge? A: Yes, it can be used relatively easily even without specialized knowledge. The LRTK app is designed with an intuitive UI, and operations such as starting and recording positioning, coordinate guidance, and point cloud scanning can be performed simply by pressing a button. Acquired data is also automatically transformed and saved, so no difficult calculations are required. Of course, having basic RTK knowledge will broaden its applications, but field workers should become effective quickly after learning a little about how to use it.

Q: How much does it cost to deploy LRTK? A: Exact costs depend on the model and sales format, but pricing is set to be very affordable compared with typical GNSS surveying equipment. In many cases, the required investment is only a fraction of that for expensive conventional RTK gear, making it easy for small and medium-sized companies to deploy multiple units. Additionally, basic functions of dedicated apps and cloud services are sometimes offered for free or at low cost, which helps keep running costs down. For detailed prices and plans, you can check the [LRTK official site](https://lefixea.com/) or contact distributors.