The combination of smartphones and RTK (Real-Time Kinematic) technology is drawing attention for overlaying design drawings onto real-world scenes using AR (augmented reality) on construction sites. Traditionally, rework has occurred due to misreading drawings or construction errors, but visualizing plans with AR can address these issues. Introducing drawing AR overlays as part of on-site DX (digital transformation) smooths consensus-building among stakeholders and enables precise construction management with fewer personnel. This article, with a volume of over 7,000 characters, explains in detail the value of smartphone × RTK drawing AR overlays, concrete implementation methods, use cases, and the effects brought to the field.

Table of contents

• Value and challenges of drawing AR overlays

• What high-precision positioning smartphone + RTK enables

• Linking design drawing data and the mechanism of AR overlay

• AR use cases on construction sites

• Accuracy and simple operation of smartphone surveying (using monopods and spike tips)

• Applications to 3D point cloud measurement and heat map analysis

• Cloud sharing and office use

• How on-site DX promotes workstyle reform and addresses labor shortages

• Getting started with high-precision, simple surveying using smartphone RTK

• FAQ

Value and challenges of drawing AR overlays

It is important to construct according to design drawings on construction sites, but paper drawings or 2D drawings have limits for sharing images on site. Even if positions are indicated by surveying or marking out, it is difficult to visualize the finished form, so there was a risk of construction errors due to human interpretation mistakes. With drawing AR overlays, you can superimpose design drawings or 3D models onto the site view through a smartphone or tablet screen. This allows an intuitive comparison of the “design intent” and the “site conditions,” enabling on-the-spot detection of dimensional or positional deviations and helping to prevent construction mistakes.

Projecting the completed image onto the site with AR also greatly facilitates consensus-building with clients and site staff. For example, in river or road renovation projects, showing the completed appearance with AR lets all stakeholders share the finished image and makes explanations smoother. Moreover, using drawing AR overlays can reduce personnel for confirmation tasks that used to require multiple people such as surveyors and construction supervisors. Because one person can perform AR display and position checks, quality control can be carried out efficiently even on sites with labor shortages.

What high-precision positioning smartphone + RTK enables

Combining smartphones with RTK positioning enables high-precision positioning that overturns previous assumptions. RTK is an error-correction technology based on GNSS (satellite positioning) that can reduce errors that were several meters with standalone GPS to below a few centimeters (below a few inches). In recent years, improvements in smartphone GNSS chip performance, augmentation signals from QZSS (Quasi-Zenith Satellite System), and the use of network reference station services have made RTK positioning possible on smartphones without dedicated equipment.

Conventional surveying required a total station or high-performance GNSS receiver, which were large and heavy and assumed two or more workers. They also required annual calibration and manufacturer maintenance, which meant sending equipment off and extra hassle. With smartphone + RTK positioning, you only need a smartphone-sized receiver and a dedicated app to carry to the site and perform one-person, immediate positioning work. For example, by attaching a dedicated compact GNSS receiver like the “LRTK Phone” (approximately 165 g) to an iPhone and launching the app, you can obtain precise position information with geographic coordinates. Field trials have shown that LRTK positioning results recorded comparable accuracy, with errors within 5 mm (0.20 in) compared to Class-1 GNSS surveying instruments, confirming it is sufficiently practical for site use.

Linking design drawing data and the mechanism of AR overlay

So how do you realize AR overlays of design drawings based on the high-precision position information obtained? The key is the linkage of digitized design data and the AR display capabilities of the smartphone app. Specifically, construction drawings (for example: CAD DWG files or BIM/CIM 3D data) are uploaded to a cloud service in advance and synced to the smartphone’s dedicated app. On the app, the imported drawing data are associated with the real-world coordinate system so they can be superimposed on the smartphone camera view.

Because the smartphone’s position and orientation are determined accurately in real time by RTK, there is no misalignment between the digital drawing and reality. Conventional AR features required placing markers on site each time or manual alignment, but combining high-precision positioning enables markerless alignment and consistently accurate overlay displays. For example, importing AutoCAD drawing data to the smartphone via the cloud and launching the app on site will project design lines and structural models at full scale in the actual location. Boundary lines and reference lines can also be displayed in AR, allowing instant confirmation of their relationship to terrain and existing structures. By linking design data with AR overlays, you can perform intuitive checks that are not possible by merely holding a drawing on site.

AR use cases on construction sites

In practice, drawing AR overlays are beginning to be used across various construction sites. Here are some representative use-case examples.

• River and revetment works: For embankment or revetment block installation, AR is used to project design alignment lines and completed models on site to confirm finishing positions. For example, you can visualize whether embankment height or slope matches the design and ensure supervisors and crews share the same understanding. Showing the completed form in AR strengthens explanations to clients and helps consensus-building at the planning stage.

• Pile driving work: For bridge foundations or large-structure piling, you can import pile position coordinates from drawings into the smartphone and display pile installation positions in AR on site. Workers can position piles precisely by following target marks shown on the smartphone screen. RTK-enabled apps with a “coordinate navigation” function can guide workers to specified coordinates, enabling a single person to efficiently handle pile-center positioning tasks.

• Slope works: For tunnel excavation or road slope shaping, you can visualize design cut-and-fill slopes in AR and compare them with current terrain. When you point a smartphone, the design slope surface is superimposed on the actual slope, so you can instantly see whether the slope under construction matches the design. For large-scale slopes where it’s hard to check the whole shape from a distance, AR makes design lines emerge even from a remote vantage point, allowing verification from a safe location.

• Road and pavement works: AR overlays are also useful for road widening or pavement replacement. Drawing the design horizontal alignment and finished elevation on site lets you check whether curves and widths match the plan. In urban roadworks with many underground utilities, showing buried pipes or cable routes in AR from the drawing helps warn against wrong excavation locations. These uses make spatial understanding easier, including unseen parts, reducing construction mistakes and rework.

Accuracy and simple operation of smartphone surveying (using monopods and spike tips)

Surveying with a smartphone and a compact RTK receiver offers high accuracy while keeping on-site operation simple. As mentioned above, RTK reduces errors to below a few centimeters (below a few inches) under favorable conditions, allowing positioning within roughly a few centimeters. Because it achieves accuracy comparable to dedicated equipment, it can be trusted for construction management tasks such as batter board locations and as-built measurement.

The smartphone’s ease of use stands out. For example, if you attach a bubble-level attachment and a spike tip (a pointed metal tip) to a monopod, you can touch the spike tip to the point you want to measure and press a button on the screen to capture the coordinate of that point. The smartphone app can apply offset correction between the spike tip and the GPS antenna position, so if the device is held vertically you can perform point surveying without error. Single-point surveys that traditionally required two people with a pole can now be done with a smartphone in one-handed operation, which is a significant advantage. When recording multiple points while walking, you can tap to record each point with one hand, so even users with little surveying experience can intuitively operate it.

Applications to 3D point cloud measurement and heat map analysis

The smartphone × RTK platform demonstrates power not only for AR display of design drawings but also for 3D scanning and measurement. Modern smartphones (especially the latest iPhones and iPads) are equipped with LiDAR sensors and high-performance cameras, enabling capture of site shapes as point cloud data. Combined with RTK’s precise position information, the acquired point clouds become 3D survey data with absolute coordinates such as latitude, longitude, and elevation. For example, even for a wide slope, you can walk while waving the smartphone for about 1–2 minutes and capture a high-density point cloud of tens of thousands of points. Even on 100 m-class (328.1 ft) long slopes, walking key routes can produce a 3D model capturing surface undulations in a short time.

The captured point cloud data can be used on site for volume calculations and shape comparison analyses. For instance, by comparing the current point cloud with the design data, you can visualize differences in planned earthwork volumes using a heat map (color distribution map). By intuitively showing “where and how much fill/cut is needed” by color, it becomes easier to instruct heavy equipment operators and verify as-built conditions. Complex earthwork calculations are obtainable in seconds by pressing a button in the app, enabling non-specialist site staff to instantly check volumes and as-built status. Additionally, the acquired point cloud can be saved and submitted as electronic deliverables, positioning it as a measurement method consistent with the Ministry of Land, Infrastructure, Transport and Tourism’s “as-built management guidelines.” As-built measurement, which previously required artisan skills, is being digitized to improve efficiency and reduce labor.

Cloud sharing and office use

Survey data and AR use captured on a smartphone are not confined to the site. Integration with cloud services makes data sharing and collaboration between the field and the office easy. Point clouds, coordinate information, photos, and other data captured by the dedicated smartphone app can be uploaded to the cloud with a single button. Uploaded data can be immediately viewed from an office PC via a web browser. For example, if positioning-tagged photos taken on site are synced to the cloud, the office can visually identify shooting locations on a map or corresponding street-view and remotely understand site conditions.

Cloud platforms allow display of uploaded point clouds and measured points in 2D maps or 3D viewers, enabling measurement of dimensions or checking cross-sections. They also support overlaying multiple point cloud datasets and design 3D models, which is useful for office-based comparison of as-built and design. For example, overlaying scanned fill point clouds with the design model on the cloud enables instant design comparison and volume checking. Because everything can be handled in a browser without expensive specialized software, the barrier to data utilization is greatly reduced.

Cloud integration also streamlines report generation and form output. Lists of surveyed point coordinates and memo-linked photos can be exported as automatically formatted PDF reports. For instance, exporting a set of location-tagged photos from inspection work produces a report organized by date and location with one click. Report creation that site supervisors previously compiled manually is simplified, reducing administrative workload. By directly connecting the field and cloud, field–office collaboration is strengthened, accelerating the construction PDCA cycle and improving quality.

How on-site DX promotes workstyle reform and addresses labor shortages

The spread of drawing AR overlays and smartphone surveying contributes to workstyle reform and alleviating labor shortages in the construction industry. First, enabling one person to complete surveying and as-built checks means sites with labor shortages can operate with minimal staff. Even without veteran technicians, smartphone apps can supplement surveying know-how, allowing younger or non-specialist staff to work with a certain level of accuracy. This can be an effective countermeasure against the decline of skilled workers.

Reducing physical burdens such as carrying heavy equipment or spending long hours marking out improves technicians’ working conditions. Automatic recording of survey results and automatic report generation can reduce overtime, contributing to better work–life balance. Sites that make skilled use of digital tools also appear more attractive to younger workers, improving the industry’s image and helping attract new entrants. Furthermore, real-time sharing of site conditions allows checks that previously required on-site presence to be performed from a desk, reducing management burdens for remote projects. Promoting on-site DX helps create worker-friendly environments and is expected to mitigate chronic labor shortages.

Getting started with high-precision, simple surveying using smartphone RTK

Finally, here are points to consider when introducing high-precision surveying using smartphone × RTK. The market now offers solutions combining compact smartphone-compatible RTK receivers with dedicated apps; a representative example is LRTK. LRTK is an integrated platform that completes positioning, point cloud measurement, and drawing AR with just a smartphone, and it is notable for being less expensive than conventional equipment. By attaching dedicated hardware to the smartphone and launching the app, centimeter-class positioning is immediately available, allowing anyone to start using it easily.

Such smartphone RTK solutions are compact and portable, adaptable to many on-site scenarios. Even companies without specialized surveying departments can have site supervisors or construction managers perform accurate measurements themselves, promoting the democratization of high-precision surveying. In practice, many construction companies and consultants are beginning to feel the efficiency gains from smartphone RTK, with some saying “once you use it, you can’t go back to the old way.” If your company is considering introducing drawing AR overlays or smartphone surveying as part of DX measures, there’s no reason not to take advantage of these latest tools. Consider adopting the evolving smartphone × RTK technology to achieve both precision construction and operational efficiency.

FAQ

Q: What equipment and preparation are needed to perform drawing AR overlays? A: Basically, you need an RTK-capable GNSS receiver, a smartphone, and a dedicated AR display app. For example, prepare a compact RTK receiver that can attach to a smartphone and an app that supports that receiver. You also need to preload the design drawing data to be overlaid (DWG, LandXML, or 3D models such as IFC) into the app or cloud. If you have an environment to receive correction information via a network, a smartphone alone (plus the receiver) can perform real-time high-precision positioning and AR display.

Q: Is the accuracy of RTK positioning using a smartphone really sufficient for construction? A: Yes. The latest smartphone + RTK solutions can achieve centimeter-level accuracy. Under good conditions, errors often fall within 1–2 cm (0.4–0.8 in), which is sufficient for setting out structures and as-built verification. In fact, comparison tests with dedicated surveying equipment have shown smartphone RTK positioning errors on the order of a few millimeters. With proper equipment setup, you can perform site positioning with accuracy comparable to conventional total stations.

Q: How does this differ from conventional total station or GPS surveying? A: The biggest differences are ease of use and one-person operation. Total stations are highly accurate but require expert setup and calibration and take significant time and personnel. Smartphone RTK starts positioning as soon as you launch the app and acquire satellites, allowing one person to carry it and obtain coordinates at will. Smartphones also offer integrated functions such as on-site AR display and point cloud scanning that dedicated equipment lacks. Whereas dedicated instruments often required post-processing on a PC, smartphone RTK enables seamless surveying, visualization, and analysis on the device. Cost-wise, a smartphone plus a compact receiver is less expensive than conventional equipment and reduces operating costs.

Q: Can I use my existing design data (CAD drawings or BIM models)? A: Yes, you can use existing CAD data and BIM models. Many smartphone RTK-compatible apps can import 2D drawings such as DWG or DXF and 3D models in LandXML or IFC formats. By syncing data via the cloud and displaying it in the site coordinate system, design drawings created during the design phase can be used directly for AR overlays. However, if the drawings are not aligned to the survey coordinate system, you may need to fit them to known points on site.

Q: Is positioning and AR display possible indoors or where GPS signals do not reach? A: High-precision RTK positioning is difficult in environments where GPS cannot be received directly, such as indoors or inside tunnels. However, there are several countermeasures. Indoors, you can perform relative alignment based on pre-installed known-point markers, or temporarily position using the smartphone AR kit’s visual-inertial odometry. Accuracy will be lower than satellite-based positioning but can be sufficient for short ranges. There are also systems under research that provide pseudo-satellite signals indoors or use QR-code-based positioning. In the future, technologies enabling seamless positioning and AR display both indoors and outdoors are expected to become widespread.

Q: What are the initial and running costs? A: The introduction cost of smartphone RTK solutions tends to be lower than that of conventional surveying equipment. High-precision GNSS receivers or total stations can cost several million yen, whereas compact smartphone RTK receivers are substantially cheaper. App and cloud service fees are also generally more affordable than specialized software. For example, LRTK offers plans with unlimited cloud features for a fixed fee. Additionally, indirect cost benefits from reduced labor and increased efficiency are substantial, so initial investment can be recovered relatively quickly.

Q: How can the measured data be utilized? A: Coordinates and point cloud data acquired with smartphone RTK have many uses. You can import point clouds into CAD software for as-built management and comparison with design models or use them for earthwork volume calculation. Position-tagged photos taken on site serve as evidence in reports. Sharing data on the cloud makes remote checking and consulting easy. Organizing data as electronic deliverables is also useful for subsequent design changes and maintenance.