Can a smartphone become a surveying instrument on-site? The secret to labor savings enabled by AR inspection

Table of contents

• Challenges of conventional surveying and inspection

• How smartphones and AR technology change on-site surveying

• High-precision surveying for anyone with iPhone + RTK

• Intuitive as-built verification with AR inspection

• Use cases of AR technology and benefits of labor saving

• Introducing simple surveying with LRTK

• FAQ

Challenges of conventional surveying and inspection

Surveying and as-built inspection at construction sites have long relied on manual work by skilled technicians. Using dedicated surveying instruments such as total stations and levels, experienced surveyors needed to spend days carefully performing tasks from establishing control points to measuring each survey point and checking against drawings. However, several issues with conventional methods have been pointed out.

• Time-consuming work: Because of the analog process of setting up equipment and measuring point by point, vast amounts of time were required when sites were large or there were many locations. It was not uncommon for it to take several days to bring the measurement results back to the office, organize them, and prepare reports.

• Dependence on manpower and skilled technicians: Accurate surveying requires experienced surveyors or technicians, and in many cases work had to be done by teams of at least two. The construction industry faces serious labor shortages and an aging workforce, making it difficult to always have veterans on site.

• High equipment costs: High-precision surveying requires expensive specialized equipment such as total stations and RTK-GNSS receivers, with initial investments amounting to millions of yen. Small and medium-sized companies or small sites often find purchases difficult, and outsourcing to specialists is also a financial burden.

• Measurement errors and recording mistakes: Manual processes are prone to human error. Mistakes can occur when copying measured values on site, and small errors can accumulate over multiple measurements. If measurement mistakes are noticed later, inefficient rework and return trips to the site can occur.

• Difficulty surveying hazardous locations: Surveying is difficult in locations where people cannot easily enter, such as high slopes, under bridges, or narrow tunnels, sometimes forcing risky attempts to measure. As a result, some areas remained unmeasured and quality checks were insufficient.

• Burden of report preparation: After surveying and as-built inspection, it is necessary to create drawings and forms based on the acquired data. Large amounts of office work such as entering numbers into Excel, tracing drawings in CAD, and organizing photos are generated, placing a heavy burden on site supervisors.

• Delayed detection of problems: Even if there are as-built defects (insufficient thickness or incorrect slope), they are often not discovered immediately on site and are only noticed after bringing the data back. Delayed correction instructions can lead to extra repair costs or schedule extensions after construction.

As described above, conventional surveying and inspection methods were labor- and time-intensive, lacked real-time capability, and relied heavily on specialists. To solve these issues, the industry as a whole is promoting the introduction of ICT technologies and *i-Construction*. Among them, the use of AR technology is attracting great attention as a trump card that can simultaneously realize labor savings and quality improvement on site.

How smartphones and AR technology change on-site surveying

AR (Augmented Reality) technology overlays digital data such as 3D models or textual information onto the real-world view seen through a camera. Once mainly used for research, AR has evolved to a level that can be used in everyday field operations thanks to improvements in the performance of smartphones and tablets. Modern iPhones and iPads are equipped with high-performance cameras and LiDAR sensors (laser-based 3D measurement sensors), and by leveraging these, it has become possible to intuitively “visualize” the site.

Use of AR is expanding in the construction and civil engineering fields. Information that was difficult to share using only drawings and numbers can be visualized over the actual view on site, making it easier for all stakeholders, including clients and craftsmen, to share the same image. For example, if a model of a completed structure is displayed life-size on site in AR, everyone can instantly understand the finished form that is hard to grasp from paper drawings. Communication losses are reduced and rework caused by misunderstandings is easier to prevent. Truly, a picture is worth a thousand words, and consensus building, as well as the accuracy and speed of instructions on site, are expected to improve dramatically.

In particular, recent attention has focused on applying smartphone AR to surveying and as-built inspection. If a smartphone everyone is familiar with becomes a surveying tool, anyone on site can participate in surveying and inspection tasks. Data obtained can be shared immediately via the cloud, enabling quality checks during construction. As a concrete measure to address issues such as lack of experienced personnel and lack of real-time capability, this AR technology is expected to be a major driving force for on-site DX (digital transformation). AR applications that can achieve both labor savings and quality assurance are now beginning to revolutionize field work styles.

High-precision surveying for anyone with iPhone + RTK

You might worry, “Smartphone GPS accuracy is unreliable.” Indeed, the positioning accuracy of typical built-in smartphone GPS is on the order of several meters (several ft), and is far from the accuracy needed for traditional surveying. The key technology here is RTK (Real Time Kinematic), a high-precision positioning technique. RTK uses correction information from a base station to reduce GPS errors to on the order of several centimeters (a few in). In Japan, environments for easy use are becoming available by using augmentation signals such as CLAS from the Quasi-Zenith Satellite System “Michibiki.”

The combination of smartphone + AR + RTK is the secret to “easy, high-precision surveying for anyone.” Specifically, a small high-precision GNSS receiver (RTK-compatible GPS antenna) is attached to a smartphone, and a dedicated app applies correction to the positioning information. For example, attaching and linking Reflexia’s small device “LRTK Phone” to an iPhone allows the smartphone to measure its own position with accuracy within 2-3 cm (0.8-1.2 in). Furthermore, scanning the surroundings with the smartphone’s built-in LiDAR and camera enables high-precision coordinates to be assigned to all acquired point cloud data and photos. As a result, measurements of distance, height, area, volume, etc. taken with a smartphone can be calculated with accuracy comparable to conventional surveying instruments.

In other words, a smartphone transforms into a high-performance surveying instrument. Modern iPhones also have robust communication capabilities and can automatically obtain public reference station data and satellite correction signals over the network to correct positioning accuracy in real time. No complicated settings or cable connections are required; attach the device to an iPhone on site, turn on the power, and centimeter-level positioning (cm level accuracy (half-inch accuracy)) can start within tens of seconds. There is no need to carry heavy tripods or set instruments with bubble levels—the convenience of completing the work with just a smartphone and a palm-sized antenna is unparalleled. With advanced measurement achievable at the push of a button, site staff can perform surveying and as-built verification themselves without special skills. Tasks that were previously left to specialists or surveyors can now be handled in-house, dramatically reducing the effort and barriers of surveying. Indeed, the surprising change of “surveying with a smartphone being this easy!?” is beginning to occur on sites.

Intuitive as-built verification with AR inspection

One major strength of smartphone surveying is the ability to perform intuitive as-built inspections using AR technology. Traditionally, as-built inspection required comparing numerical survey data obtained on site with drawings, and determining “where discrepancies occur” required specialized knowledge. Numbers on paper are hard to grasp intuitively, and it was not easy to immediately judge pass/fail on site.

However, using a smartphone and AR, measurement data and design data can be overlayed and inspected visually on the spot. For example, when checking whether the road surface after paving has been finished to the design elevation, simply viewing the actual surface through an iPhone screen can reveal differences from the design model as a color-coded heat map. Areas within tolerance are shown in green or blue, while areas with insufficient thickness or excessive buildup are shown in red or warm colors, allowing instant assessment of construction quality at a glance. Even without specialist knowledge, workers can intuitively understand where corrections are needed by simply observing color differences.

Furthermore, the AR-based as-built check can be recorded and shared as photos or videos directly with the smartphone. If defects are found, images of the red areas on the heat map can be shared within the team and repair work can begin immediately, allowing rapid PDCA to be completed on site. Previously, defective areas were identified after bringing survey data back to the office, but AR enables this to be done in real time on site, a major efficiency improvement. Quality can be checked immediately after construction and corrected on the spot, greatly reducing rework and improving quality assurance.

Use cases of AR technology and benefits of labor saving

Let’s look at some concrete examples of the new construction management made possible by smartphone + AR surveying, and the labor-saving effects gained from them.

• Visualize the entire site with 3D point cloud scanning: Using a smartphone’s LiDAR, simply walking around the site can record surrounding terrain and structures as a vast number of points (point cloud data). One scan can acquire measurement points on the order of millions, enabling 3D modeling of complex slope shapes or vast development sites that could previously only be partially measured. Distances, areas, and volumes can be calculated immediately from the acquired point cloud, allowing earthwork calculations and as-built quantity management to be handled on site. There are cases where surveying that used to take two days was completed in half a day, leading to significant time savings and labor reduction.

• Real-time as-built management: With smartphone AR, it is possible to instantly check on site whether the post-construction shape matches the design. If point cloud data and the 3D design model are automatically compared in the cloud, a color-coded heat map showing discrepancies can be generated quickly. Displaying that on site in AR makes it immediately clear where the surface is higher or lower than the design. For example, if an embankment has excess or deficiency, it can be identified immediately after construction and decisions on additional fill or cutting can be made at once. This greatly contributes to preventing overlooked defects and reducing rework, transforming as-built inspection into real-time quality control.

• AR-guided stake placement and layout: Traditionally, layout and height were determined using batter boards and marking, reading drawings to find structure positions. Smartphone AR can directly display design position information over the real-world view as a guide. For example, drawing boundary lines on the ground in AR allows all workers to intuitively share the shape of curves and parcel sizes on site, preventing measurement mistakes and construction errors. If stake coordinates are registered in advance, the smartphone screen can show directional arrows so even inexperienced workers can accurately locate stake positions without confusion. AR guidance ensures points are not missed even when markers are obscured by vegetation or snow, enabling efficient layout work by a single person.

• Visualize errors with heat maps + AR: Heat maps that use color gradients to indicate differences between design and as-built are powerful tools for as-built inspection. Green or blue indicates acceptable range, red tones indicate positive error, and blue tones indicate negative error, making it easy to intuitively grasp surface irregularities. Overlaying a heat map in AR on the actual structure allows immediate on-site identification of defects that are hard to detect from drawings. Because repairs can begin without marking the surface with physical markers, the workflow from inspection to correction becomes smooth. The combination of heat maps and AR is evolving as-built inspection from mere record-keeping into a tool for immediate quality improvement.

As the above use cases demonstrate, smartphone AR surveying is powerful in all scenarios including earthworks, paving, land development, and structural construction. Point cloud scanning and AR visualization dramatically streamline the “measure and verify” process, while also contributing to improved accuracy and safety. Finally, let’s summarize the main labor-saving benefits gained by introducing such AR inspection.

• Reduced personnel and labor savings: Surveying and inspection can be completed by a single person or a small team, greatly reducing required manpower. Even sites short of experienced surveyors can be managed by younger staff.

• Shortened man-hours and increased efficiency: Automatic measurement via point cloud scanning and instant confirmation with AR can dramatically shorten the time from surveying to inspection. Confirming quality on site and performing corrections immediately helps shorten overall project schedules.

• Standardization and quality improvement: Digital tools enable consistent data acquisition and evaluation regardless of who performs the measurement. Standardized quality control free from individual dependence can be realized, and visualization of construction based on objective data improves the accuracy of quality checks.

• Utilization of young workers and skill transfer: Smartphone-centered operations are intuitive for the digital generation, expanding opportunities for young workers on site. Certain accuracy can be assured even without veteran know-how, helping to close the skill transfer gap. Using the latest technologies can also boost young workers’ motivation.

• Improved safety and cost reduction: Lighter, simplified surveying equipment reduces workload and accident risk in hazardous locations. Personnel reductions and simplified equipment can also reduce labor and equipment costs.

Introducing simple surveying with LRTK

In construction sites where labor shortages are a pressing issue, smartphone surveying and inspection using AR is a promising new technology that can be a trump card for labor savings and productivity improvement. With the combination of an iPhone and a small RTK device, anyone can measure a site like a surveyor and evaluate as-built conditions on the spot. By adopting new solutions rather than sticking to traditional methods, it is possible to achieve both labor reduction and quality assurance and accelerate DX on construction sites. Smartphone surveying also directly connects to on-site utilization of design data such as BIM/CIM, serving as a bridge between drawings and the field.

If you are experiencing issues with your current surveying or as-built management, consider introducing smartphone surveying with LRTK. This approach, which leverages smartphones and AR technology, should be a powerful solution for improving on-site productivity and addressing labor shortages. With advanced AR technology and easy smartphone operation, let’s smartly and powerfully update future surveying and inspection work.

FAQ

Q. What is AR inspection? A. AR inspection is a method in which design data and measurement data are overlayed and checked through a smartphone camera on site. It visualizes as-built errors that are hard to see from drawings or numbers, allowing intuitive on-site checks.

Q. Can accurate surveying really be done with a smartphone? A. Yes — by combining a high-precision GNSS receiver with RTK correction technology. For example, using an LRTK device can provide centimeter-level positioning with a smartphone. This enables measurement of positions and distances with accuracy comparable to conventional surveying equipment.

Q. What equipment and preparations are required for introduction? A. Basically, you need an iPhone or iPad with LiDAR, a high-precision GNSS antenna (RTK-compatible), and a dedicated surveying app to get started. Even without an internet connection, devices like LRTK that can receive correction information directly from satellites can provide stable positioning in mountainous areas. Complicated setups or installations that used to be required are no longer necessary, making operation easy with minimal equipment.

Q. Can workers who are not tech-savvy or older staff use it? A. Yes, systems are designed to be usable without specialized knowledge. Even those with limited surveying experience can operate intuitively by following the smartphone screen’s guidance. Complex device operations and calculations are automated by the system, so older workers can also start using it on site shortly after training.

Q. Can survey data obtained with a smartphone be submitted as official inspection materials? A. Yes. Point cloud data and photos acquired with the LRTK system can be output in formats consistent with the Ministry of Land, Infrastructure, Transport and Tourism’s “As-Built Management Guidelines (Photogrammetry Edition).” With high positioning accuracy and data quality ensured, the deliverables can be used on par with conventional inspections. Storing and sharing electronic data is also easy, improving the efficiency of report preparation.