Achieving Solo Surveying with LRTK Positioned Photos: Greatly Improving On-Site Efficiency

Table of Contents

• Challenges of Conventional Surveying: Labor and Time Burdens

• What Is a Positioned Photo?

• Achieving Solo Surveying with LRTK Positioned Photos

• Key Points Where Positioned Photos Improve On-Site Efficiency

• Recommendation for Simple Surveying with LRTK

• FAQ

In recent years, expectations for solo surveying in construction and civil engineering sites have been rising. Surveying has traditionally been carried out by multi-person teams, but advances in technology have made it possible for a single person to complete highly accurate surveys. This article focuses on the key term “positioned photo” and uses the latest solution LRTK as an example to explain how solo surveying can be achieved and what benefits it brings. We clearly introduce next-generation surveying methods that can improve on-site productivity and support work-style reform.

Challenges of Conventional Surveying: Labor and Time Burdens

Surveying on construction sites is an essential process to ensure that completed structures and terrain match the design drawings. However, conventional surveying methods have several issues. First, specialized surveyors and multiple personnel are required: when operating instruments like total stations or levels, it is common for one person to operate the measuring device while another holds the pole, making it a team task. Therefore securing personnel is essential, and this is a major burden in times of worsening labor shortages. Also, because each point must be measured carefully, the work time is long, and wide sites tend to require a huge number of measuring points, meaning surveys can take days to weeks. Under such circumstances, only limited points are measured and omissions in measurement can lead to problems discovered later. Furthermore, manually measuring and recording things like elevation differences and thicknesses on site is prone to human error; for example, forgetting to take photos or making recording mistakes have been quality-control issues.

Thus conventional surveying faced the problems of “requiring manpower, taking time, and carrying risks of omissions and errors.” Within the *i-Construction* and construction DX initiatives promoted by the Ministry of Land, Infrastructure, Transport and Tourism, on-site digitization is sought to solve these issues. Emerging in this context is an approach to simple surveying that leverages new technologies in smartphones and GPS (GNSS).

What Is a Positioned Photo?

A “positioned photo” is a method of recording the shooting location with high accuracy at the same time as taking a photograph. Normally, photos taken with smartphones include location information (geotags), but that error is generally about 5–10 m (16.4–32.8 ft) and too coarse for precise surveying. Positioned photos, on the other hand, use real-time positioning technology called RTK (Real Time Kinematic) to obtain centimeter-level position coordinates (inch-level) and tag the photo with them. For example, using an LRTK system, simply taking a photo with an iPhone camera will record the latitude, longitude, and elevation of the shooting point with an accuracy of a few cm (a few in). In addition, the shooting orientation (camera direction) is also saved simultaneously, so you can know which direction the photo was taken.

With positioned photos, the photo and survey data become integrated. If you photograph a point of interest on site, the photo itself functions as a precise survey point record. Conventionally, one would measure coordinates with surveying instruments, then separately record them in notes or drawings and take photos as needed—multiple steps. With positioned photos, you can obtain location and image in a single action by pressing the shutter, greatly reducing labor. For example, in crack inspections of concrete structures, photographing the crack alone allows the exact position to be recorded on a map. In disaster site documentation, each photo taken is saved to the cloud with geographic coordinates, making it easy to later check the damage area on a map or share it with multiple people.

In short, a positioned photo is a “photo with high-precision location information.” The key to enabling this is RTK positioning technology, realized by combining a dedicated high-precision GNSS receiver and a smartphone app.

Achieving Solo Surveying with LRTK Positioned Photos

So how does using LRTK positioned photos allow a single person to complete surveying work? Here we explain why solo surveying is possible, based on an overview of LRTK system features.

LRTK comprises an ultra-compact RTK-GNSS receiver device called the “LRTK Phone” that attaches to a smartphone (currently mainly iPhone/iPad), a dedicated smartphone app that handles positioning data, and a cloud service. When you attach the LRTK receiver to your phone and launch the app, centimeter-class positioning begins immediately by using network RTK correction information (virtual reference station data via Ntrip) and Japan’s Quasi-Zenith Satellite System *CLAS* signals. RTK corrects error factors that cannot be removed by standalone positioning in real time, allowing you to determine your position on site with astonishing accuracy of about 1–2 cm (0.4–0.8 in).

Once positioning stabilizes into a high-precision state called a “fixed solution,” measuring and recording tasks can be completed with just the smartphone. The LRTK app provides an intuitive user interface, letting you perform positioning and data recording with simple taps. For example, to record the coordinates of a point, tap the “Record Point” button to save your current position, and if you want to acquire points continuously, switch to continuous measurement mode and simply walk around to capture a point cloud (a collection of many points). This makes it easy for one person to walk a wide area and perform a 3D scan of the terrain.

Particularly powerful is the positioned photo function mentioned earlier. When you take a photo with the phone camera, the photo file is automatically tagged with the high-precision position coordinates and orientation obtained by RTK. If you find something noteworthy on site, just taking a photo completes the surveying of that location. For example, when recording the installation status of pipes or piles on a construction site, keeping only photos with coordinates allows you to later plot positions on drawings without the need to measure each with a tape or surveying instrument. Moreover, cloud integration is available with one tap, so photos and coordinates can be shared with the office and stakeholders immediately after shooting.

The LRTK app also includes AR (augmented reality) features for non-contact positioning and guidance navigation. For example, you can display a virtual marker or stake over the phone screen for a recorded point and, as you move toward it, see the distance update—this guides you to the target. This allows staking and layout tasks to be done by one person. AR subject positioning also enables designating a distant target in the camera view and calculating its coordinates. With this, you can obtain coordinates from afar without approaching hazardous or inaccessible locations. Points that previously required someone to go into danger to set a prism or mark can now be measured safely by one person with LRTK.

As described above, using a smartphone RTK system centered on LRTK positioned photos allows a single person to handle “measuring,” “indicating,” and “recording.” The fusion of high-precision GNSS positioning and smartphone apps means that processes once dependent on surveying teams can now be completed by on-site personnel themselves.

Key Points Where Positioned Photos Improve On-Site Efficiency

LRTK positioned photos and smartphone surveying dramatically improve on-site work efficiency. The main points are summarized below.

• Reduced personnel: The biggest advantage of enabling solo surveying is reduced manpower. Because a single on-site person can acquire data without assembling a surveying team, personnel can be allocated to other tasks. There are reports from sites that “because one person can do it, others were reassigned to different tasks and productivity improved,” allowing projects to progress efficiently with limited staff.

• Shorter working hours: Positioned photos complete surveying at the moment of shooting, greatly reducing working time compared to conventional methods. Even when measuring many points, continuous measurement while walking can cover a wide area at once. At some sites, surveys that used to take several people a full day have been completed in minutes with smartphone point-cloud scanning. Because results are obtained immediately, quality checks and decisions about the next steps can be made quickly on site.

• Improved data coverage: Using positioned photos and point-cloud surveying enables high-density measurement of the entire site, reducing missed measurements. Where conventional work measured only key points, continuous data now allows you to record the whole site. This prevents situations where unmeasured defects are discovered later and increases the likelihood of passing inspections on the first attempt.

• Enhanced safety: Solo surveying and non-contact positioning reduce measurement risks in hazardous locations. On steep slopes or beside busy roads, you can obtain coordinates from a safe distance via photographic surveying or AR, reducing the number of times workers must enter danger zones. This directly contributes to preventing occupational accidents.

• Real-time sharing and utilization: Positioned photo data can be shared and stored via the cloud instantly. This eliminates the need to bring field data back to the office for processing, allows office staff to monitor site status remotely, and enables multiple people to check and provide feedback simultaneously. Immediate data sharing speeds decision-making and reduces rework and waiting time.

From these points, it is clear that smartphone surveying technologies, including positioned photos, outperform conventional methods in efficiency, accuracy, and safety. They dramatically reduce the personnel and days required for surveying while yielding high-quality data, thereby improving overall site productivity.

Recommendation for Simple Surveying with LRTK

As shown so far, combining smartphones and RTK technology is bringing a major transformation to the surveying world. By introducing solutions like LRTK, tasks that were previously left to specialized surveying teams can be converted into simple surveying that anyone can perform easily. Without being troubled by complex equipment operations or cumbersome procedures, site personnel themselves can obtain the necessary data on the spot and use it immediately.

The advantage of RTK surveying with a smartphone is not only improved work efficiency but also the potential to change the way work is done on site. For example, processes that could not proceed until a surveyor arrived can now be advanced quickly by site technicians’ decisions. Also, because survey results are shared digitally in real time, new forms of collaboration become easier, such as multiple remote participants simultaneously providing immediate feedback. The slogan “one surveying device per person” is becoming popular, and the day when smartphone RTK becomes the on-site standard may be near.

Introducing new technology can bring concerns, but a key attraction of LRTK is that you can start with just your existing smartphone. If you are interested, consider trying this simple smartphone-based surveying on a small site or as a pilot deployment. Once you can freely handle centimeter-level position information, on-site productivity and creativity should leap forward. As a first step toward a future surveying style, please consider adopting LRTK.

FAQ

Q: What functionality does a positioned photo provide? A: A positioned photo is a function that performs high-precision positioning at the moment of taking a photo and tags the photo data with position coordinates. In the case of LRTK, centimeter-level accuracy (inch-level accuracy) position information obtained by the RTK-GNSS receiver attached to the smartphone is written into the photo file, so each photo records precise latitude, longitude, and elevation. The key feature is that you obtain “photos with location information” that are overwhelmingly more accurate than ordinary smartphone photos.

Q: How accurate is the position information obtained from positioned photos? A: Under favorable conditions, you can expect horizontal accuracy of about 1–2 cm (0.4–0.8 in) and vertical accuracy of about 3–5 cm (1.2–2.0 in). This is a level of precision that stands apart from conventional standalone positioning (errors of about 5–10 m / 16.4–32.8 ft). This accuracy is achieved through RTK error correction, and in open outdoor environments with clear sky, smartphone RTK has been confirmed to provide positioning accuracy approaching that of total stations. However, in environments where satellite signals are obstructed, such as dense high-rise districts or forests, temporary errors of several tens of cm (several tens of in) may occur. For critical points, we recommend rechecking with conventional instruments as appropriate to site conditions.

Q: Can surveying really be done by a single person? A: Yes. Using a smartphone surveying system like LRTK, many tasks can be completed by one person. For example, where conventionally one person operated the instrument and another held the staff, with LRTK one person can measure their own position. AR-based non-contact positioning also eliminates the need for someone to be stationed at a remote target point. Because one person can move quickly over a wide area, recording points and point-cloud scanning are especially efficient. Site managers report that “because one person can do it, other staff could be assigned elsewhere,” contributing significantly to alleviating manpower shortages and improving productivity. However, for displacement measurements that require millimeter-level precision (millimeter-level, i.e., fractional-inch precision) or in environments where satellite positioning is impossible such as indoors or underground, conventional specialized instruments remain necessary. It is ideal to use the right tool for each situation.

Q: The operation seems difficult—can people who are not good with machines use it? A: Rest assured. The LRTK app is designed with an intuitive operation system so anyone can use it easily. On a smartphone screen showing your current position on a map, simply tap the required buttons to record points or take photos. For example, “save current location as a survey point” is one tap, and “take and save a photo” is also one tap—the system automatically handles complex settings and calculations. If you are familiar with basic smartphone and map app operations, no difficult knowledge is required, and with a short training session you can start using it on site quickly. The app also includes in-app help, and support systems are in place should you get stuck.

Q: Can smartphone surveying replace conventional surveying instruments (total stations and high-precision GPS receivers)? A: It depends on the application. For general terrain surveying, as-built measurement, staking positions, and many other scenarios, smartphone RTK can be used as an alternative. Smartphone RTK is especially advantageous for wide-area surveys, sequential point recording, and acquiring photo-based point clouds where a single person can move quickly. On the other hand, for measurements that require millimeter-level precision such as settlement or displacement monitoring, or for positioning needed inside tunnels or indoors, total stations and specialized instruments are still indispensable. Therefore, smartphone RTK is often used as a new option to complement and improve efficiency alongside conventional instruments rather than as a single replacement; combining tools according to site needs is recommended.

Q: Can it be used at sites without mobile coverage, such as in mountain areas? A: Yes. LRTK receivers support CLAS (centimeter-class positioning augmentation service) provided by Japan’s Quasi-Zenith Satellite System, and can receive correction information directly from satellites even without mobile coverage. Therefore, in remote mountain areas or islands without cellular reception, centimeter-class positioning can be maintained as long as the sky is open and satellites can be captured. There are actual examples of LRTK being used for mountain forest surveys and disaster sites where mobile coverage was unavailable, demonstrating its effectiveness as a surveying tool that does not depend on communication infrastructure. However, in locations such as tunnels or building basements where satellite signals cannot be received at all, RTK positioning is naturally difficult; in such cases, combining with conventional methods or switching to ground-based surveying will be necessary.

Q: Is LRTK available for Android smartphones? A: As of 2026, the LRTK series is primarily provided for iOS (iPhone/iPad). Apple devices offer high-quality access to GNSS data and stable sensors, so the product was first released for iOS. Many users have requested Android support, and future compatibility is being considered. Please check official announcements for the latest information; at present, Android users would need to use an iOS device combined with an LRTK receiver to utilize the system. LRTK can also be used with tablets such as iPad, and there are actual examples of using an iPad with LRTK for field work.