Next-Generation Field Surveying Techniques Opened Up by AR Markers

Table of Contents

• Introduction

• What Is an AR Marker?

• Surveying Methods Using AR Markers

• Benefits of Using AR Markers

• Use Cases of AR Marker Applications

• Challenges and Countermeasures for Implementation

• The Future of Field Surveying Opened by AR Markers

• Simple Surveying with LRTK

• FAQ

Introduction

In recent years, a new keyword called "AR marker" has been attracting attention in surveying and construction sites. AR stands for "Augmented Reality," a technology that overlays virtual information on real-world images. An AR marker is a marker that uses special patterns or codes recognizable by a camera to correctly position AR virtual information in real space. By utilizing AR markers, groundbreaking field surveying methods that overturn conventional practices are becoming feasible.

Traditionally, surveying involved teams of experienced personnel operating total stations (optical surveying instruments) or GPS survey equipment on site to set out batter boards or drive stakes. However, due to labor shortages caused by an aging population and the shift toward workstyle reforms, new methods that enable one person to survey quickly and accurately are in demand. This has led to next-generation surveying approaches that leverage AR technology. This article, themed "Next-Generation Field Surveying Techniques Opened Up by AR Markers," explains in detail the mechanism and benefits of surveying using AR markers and AR technology, actual use cases, and challenges at the time of implementation. Finally, we introduce simple surveying with LRTK, a solution that allows you to easily experience this new technology.

What Is an AR Marker?

First, what exactly is an AR marker? Simply put, it is a "marker" used in AR (augmented reality) to align virtual objects. Specifically, it refers to printed shapes that are easy for a camera to recognize, such as black-and-white patterns, QR-code-like images, or illustrations. AR-enabled apps detect these markers from the camera feed and determine their position and orientation so that corresponding virtual information can be accurately overlaid in the correct location.

For example, placing an AR marker on a table and viewing it through a smartphone camera can cause a virtual character or building model to appear at that location. This technique has long been widely used with libraries like ARToolKit; marker-based methods are called "marker-based AR" (marker AR), while methods that use the shape or texture of an object directly are called "markerless AR." Marker-based AR has the advantage that as long as the marker remains in the camera view, virtual objects remain stably positioned without drifting.

In surveying, AR markers can be used to display virtual markers or models in AR at positions corresponding to real survey points or reference lines on design drawings. In other words, AR markers act as field reference points, becoming keys for aligning digital design data with the real-world coordinate system.

Surveying Methods Using AR Markers

So, what are the specific procedures and methods when using AR markers in field surveying? Here is one example of such a method.

First, place AR markers at known points on the site (reference points whose coordinates are known). Link corresponding coordinate information to the AR markers, or pre-measure the coordinates of the marker placement locations. Next, prepare a dedicated surveying app on an AR-capable device such as a tablet or smartphone and load the site’s design drawings and surveying data. On-site, launch the app and first point the camera at the AR marker to scan it; the app recognizes the marker’s position and orientation. This synchronizes the 3D space within the app with the real-world coordinate system.

Once alignment is achieved with the marker, proceed by following AR guidance displayed on the device screen. For example, key points and lines from the design drawing are virtually drawn over the camera view so it is immediately clear where they lie on site. The worker moves to the designated point while looking at the screen and marks the location or takes photos to record it. Conversely, newly observed points on site can be recorded, and those points can be displayed as markers in the camera view for confirmation.

Using AR markers for surveying enables intuitive surveying with a relatively simple setup of smartphone/tablet + AR app + AR markers. For outdoor applications requiring high-precision positioning, you can enhance device positioning to centimeter-level precision (half-inch accuracy) by attaching a high-precision GNSS receiver (RTK-capable GPS receiver) to the smartphone and receiving correction data via the network. Combining GNSS and AR markers enables AR surveying with minimal drift even over large outdoor areas, and in indoor or GNSS-denied locations you can use markers for local alignment—allowing flexible operation. As a result, a new style where one person can perform on-site surveying "while looking at the design drawings" becomes possible.

Benefits of Using AR Markers

AR surveying using AR markers and AR technology offers various advantages over conventional methods. Key benefits are listed below.

• Surveying with fewer people and in less time: Tasks that traditionally required a team and a lot of time using total stations or conventional GPS surveying can be completed by one person in a short time when using AR marker-based surveying. The need for heavy equipment setup and line-of-sight arrangements is reduced, and points can be identified instantly while walking the site, dramatically improving work efficiency.

• Intuitive and simple operation: Thanks to AR visual guidance, staff with limited expertise can intuitively find points and carry out surveying tasks by simply looking at the screen. The burden of deciphering complex drawings or performing coordinate calculations is reduced, making surveying accessible to less experienced personnel.

• Immediate verification and sharing: Survey results can be immediately visualized in AR on site and compared with design models or lines for verification. Whether measured points match design positions is obvious at a glance. You can also share the tablet screen, send screenshots or point-cloud data via the cloud, and enable real-time information sharing with remote office staff, facilitating rapid decision-making.

• Cost reduction: Rather than purchasing expensive specialized surveying equipment (high-precision GNSS receivers or total stations), a setup of a smartphone or tablet, printed AR markers, and a small GNSS receiver when needed can reduce initial investment. Renting multiple devices or paying labor costs can be avoided by adopting one smartphone per person for surveying, which is economical. Additionally, costs for printing paper drawings and rework resulting from discrepancies between design and field conditions can potentially be reduced.

• Improved safety: AR guidance allows verification of points from a safe distance or enables non-contact measurement in hazardous areas. For example, there is less need to take dangerous postures to survey at heights or on slopes, reducing the risk of falls. Also, positions can be indicated remotely without entering areas where heavy machinery is operating, contributing to worker safety.

Use Cases of AR Marker Applications

In what situations are AR markers and AR technology actually useful in surveying? Here are some concrete examples.

• Efficient stake driving and layout by one person: Traditionally, a surveying crew would move around the site to drive wooden stakes or mark lines. With AR markers and a smartphone, virtual stakes or lines corresponding to design reference points or boundaries can be displayed in AR. The worker simply moves to the points indicated on the phone screen and marks the precise locations. In confined sites or on slopes, this eliminates the need to drive physical stakes, enabling one person to quickly perform layout tasks.

• Overlaying design models in AR: 3D design models created in BIM/CIM can be overlaid on the site view. With AR marker-based alignment, full-scale models of completed roads or buildings can appear on site. When workers, managers, and stakeholders view the completed image displayed on the screen together, the completed image can be intuitively shared, helping prevent rework due to misunderstandings among operators, construction crews, clients, or local residents.

• Application to as-built and quality control: For as-built management, design cross-sections can be overlaid on the terrain in AR to compare current ground conditions with design lines. If AR markers are used for precise alignment, embankment or excavation surpluses/deficits can be visually understood on site. During inspections, virtual markers (pins) can be displayed to indicate inspection points and prevent oversights, and fixed-point observations can be guided by AR to recreate the same camera position as previous photos for recording temporal changes.

• Point-cloud scanning and volume calculation: When performing point-cloud scans (3D measurements) on a site with a LiDAR-equipped smartphone, AR marker alignment and RTK positioning are highly effective. Simple smartphone scans tend to have ambiguous positioning and distorted point clouds, but providing reference coordinates with AR markers or assigning absolute coordinates with RTK enables immediate acquisition of point clouds with accuracy suitable for as-built measurements. For example, measuring terrain before and after excavation and calculating embankment or spoil volumes from the differences can be easily performed by specifying the required area following AR guidance.

• Disaster response and remote support: At disaster sites where heavy machinery cannot enter, manual surveying may be required. Even in such situations, a smartphone combined with AR markers and a high-precision GNSS can quickly measure the terrain and damage, and share it with office technicians via the cloud in real time. In fact, some local governments in Japan have used smartphones and high-precision GNSS receivers for initial disaster recovery surveys and, even when communications infrastructure was disrupted, used the quasi-zenith satellite "Michibiki" augmentation signals (CLAS) to maintain positioning accuracy. AR markers and AR positioning technology are expected to play an increasingly active role in emergency initial surveys and remote technical support.

Challenges and Countermeasures for Implementation

Although AR marker utilization is innovative, there are challenges to consider for smooth implementation and operation. The main challenges and countermeasures are listed below.

• Matching required accuracy: The accuracy of surveying using AR markers can generally be improved to the order of a few centimeters if GNSS is used in combination. However, it is not suitable for millimeter-level accuracy management or displacement measurements. Very high-precision tasks such as control point surveying or deformation measurements still require optical total stations or high-performance laser scanners. It is important to select the appropriate method for the intended purpose and choose technology that meets the required accuracy.

• Marker visibility and environmental conditions: AR markers must be reliably captured by the camera. In dim environments, rain, or when markers are dirty or damaged, recognition accuracy can decrease or tracking may fail. To prevent such issues, use weather-resistant markers, place multiple markers so at least one is visible from any viewpoint, and periodically redo marker alignment as needed. Also, markers that are too far from the camera can be hard to recognize, so install markers in sizes and at positions appropriate to the work area.

• Dependence on GNSS environment: In downtown areas with tall buildings, forests, tunnels, and other locations where GNSS signals do not reach well, RTK positioning can be difficult. In such cases, switch to local measurement methods from nearby known points (offset measurement from known points or AR marker-based alignment), or establish RTK positioning once in an area with signal and then use IMU and AR relative positioning to propagate the position indoors in an indoor mode. Verify accuracy in advance at important points, and secure reliability by combining with conventional methods or performing redundant measurements as needed.

• Equipment handling and power management: Even though the combination of a smartphone and a small GNSS receiver is convenient, on-site use requires dustproof and waterproof protection and attention to battery management. Use mobile batteries for long work sessions to prevent power loss, and attach straps to prevent dropping the device—pay attention to basic handling. Although users will need time to become familiar with operations initially, many UIs are intuitive, so with on-site training users can become proficient in a short period.

• Consistency with existing data: When integrating coordinate data obtained from AR surveying with existing drawings or GIS data, pay attention to coordinate system consistency. In Japan, public surveying requires conformity to plane rectangular coordinate systems and geoid height standards for elevation. Confirm beforehand that the system you use supports these reference systems, and compare output data with existing coordinate values to verify there are no discrepancies. Take care to prevent positional shifts caused by initial setup mistakes.

Although there are challenges as described above, most can be overcome with appropriate countermeasures. By understanding the limits of the technology and using it wisely, you can fully enjoy the benefits of surveying with AR markers and AR technology.

The Future of Field Surveying Opened by AR Markers

With the advent of AR surveying technology using AR markers, field surveying is beginning to change dramatically. It can truly be called an innovation that "opens the future of field surveying." An era is approaching in which anyone with a smartphone and printed markers can perform high-precision surveying, and tasks that once relied on the craftsmanship of experienced workers are rapidly being digitized and automated. As the construction industry calls for DX (digital transformation) across the board—promoted by initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction—surveying using AR markers could become one of the trump cards. AR-guided surveying can contribute to improved on-site productivity, alleviation of labor shortages, quality assurance, and safety management, potentially becoming the new norm in construction management methods.

In Japan in particular, the style of one person using a smartphone surveying device to perform high-precision surveying and as-built management is gradually permeating the field. This is revolutionary compared to the past, and a system where each engineer can immediately measure, decide, and share data on site elevates project-wide efficiency and quality. Of course, AR surveying will not replace all scenarios—there will still be situations where total stations or conventional GNSS surveying are more appropriate. However, for routine civil surveying and construction management, smartphone surveying using AR markers and GNSS is expected to become a common tool. With the advancement of 5G communications and next-generation satellite positioning technologies, further improvements in accuracy and reliability are expected, and precise positioning guided by AR is no longer a futuristic concept but is becoming the current new norm.

Simple Surveying with LRTK

Finally, we introduce LRTK as a solution that allows easy experience and adoption of these AR × positioning technologies. LRTK is a high-precision GNSS positioning platform developed by a startup originating from Tokyo Institute of Technology. With the concept of "turning a smartphone into a surveying instrument with centimeter-level accuracy (half-inch accuracy)," it provides a set of a dedicated small receiver, a smartphone app, and cloud services.

For example, the palm-sized RTK receiver "LRTK Phone" attaches to a smartphone for use. It is lightweight at several hundred grams, dustproof and waterproof, and has a built-in battery. It connects to smartphones via Bluetooth or Lightning, supports RTK correction data over the network and Japan’s quasi-zenith satellite system (Michibiki) centimeter-level augmentation signals (CLAS), and enables real-time positioning with an accuracy of a few centimeters (a few inches) anywhere in Japan.

Using the dedicated "LRTK app," in addition to basic functions such as single-point positioning, continuous positioning, and averaging points to improve accuracy, you can easily use functions unique to AR-guided surveying, such as AR visualization of points, navigation, and photogrammetry using the camera (obtaining coordinate positions simply by pointing the camera at the object). Measured points are plotted on a map on site, and photos taken are tagged and saved with high-precision position and orientation information. With cloud integration, you can instantly share surveying data and photos obtained on site with the office and later display and download them as 3D in a browser—making data management one-tap easy.

By leveraging LRTK, you can perform simple surveying with just a smartphone without expensive specialized equipment. LRTK covers everything from layout to recording and data sharing in an all-in-one solution, making it easy to introduce at small to medium construction sites and surveying projects with cost benefits. Field feedback includes comments such as "LRTK made one-device-per-person smartphone surveying a reality," and it can be said to be a driving force in making AR surveying technology the new norm. If you are interested, please check LRTK’s official site for more details.

FAQ

Q: What exactly is an AR marker? A: An AR marker is a "marker" that uses a shape or pattern recognizable by a camera to place AR virtual information in real space. For example, when a camera sees a printed marker with a specific pattern, CG or guide displays appear based on that position. In surveying, AR markers placed at known points are used as references to accurately overlay design points and lines on the real site.

Q: What equipment is needed for surveying using AR markers? A: Basically, you need a smartphone or tablet mobile device, AR markers (printed markers), and a surveying app that supports AR display. For higher-precision positioning, you also need an RTK-capable GNSS receiver (high-precision GPS) that attaches to the smartphone and a communication service to obtain correction data from a reference station (via the internet or satellite). Combining these allows one person to perform high-precision AR surveying.

Q: What level of positioning accuracy can be achieved? A: Using RTK, under ideal conditions horizontal positioning accuracy of about 2–3 cm (0.8–1.2 in) can be expected. Actual field accuracy varies with satellite reception conditions and the surrounding environment, but it is dramatically higher than standalone smartphone positioning (errors of several meters (several ft)). Using AR marker alignment in combination can make the discrepancy between drawing points and the field hardly noticeable. However, millimeter-level precise measurements require other methods such as electronic distance meters.

Q: What should I do in places where GNSS does not reach? A: In areas where GNSS satellite signals are difficult to receive—such as urban canyons, mountainous areas, or indoors—RTK positioning may be difficult. In such cases, switch to methods that measure relative to AR markers installed at nearby known points, or establish RTK positioning once in an open area and then continue measurements using IMU and AR relative positioning. Also, utilizing the free augmentation signals (CLAS) provided by Japan's quasi-zenith satellite "Michibiki" can maintain a certain level of accuracy even when internet access is unavailable. It is also important to combine with conventional surveying equipment as the situation demands.

Q: Can anyone use AR surveying? Is specialized knowledge required? A: AR surveying systems are designed for intuitive operation, and basic usage is not difficult. Following on-screen guidance on a smartphone is often enough to reach points. However, knowledge of GNSS and coordinate systems makes it easier to make full use of the system, and helps understand tips for achieving accuracy and precautions. Although qualifications are not always mandatory, it is advisable to take official training or have surveys involving critical tasks conducted under the supervision of licensed surveyors in some situations.

Q: Are introduction and running costs high? A: A setup of a smartphone, a small RTK receiver, and an app often costs less than newly introducing a total station or conventional high-precision GNSS equipment. Especially if you already have tablets or smartphones, you may only need to pay for the receiver and service fees. However, obtaining RTK correction information requires contracts for communication services (such as Ntrip over the internet or satellite delivery like CLAS), which incur usage fees. That said, solutions like LRTK offer low-cost subscription plans and can make use of public free services, so consider options that fit your budget and usage frequency.