Reverse Construction Method × Smart Technology — The Next-Generation Construction Management Opened by LRTK

As digitization of construction sites accelerates, traditional construction methods are creating new value through fusion with smart technologies. A prime example is the combination of the "reverse construction method" used in underground works and the latest surveying technologies. The reverse construction method deliberately reverses the usual sequence in buildings with basement floors, constructing the above-ground and below-ground portions in parallel. It has been adopted in many large-scale projects for advantages such as shorter construction schedules and stable construction on weak ground. However, its complexity also makes it a construction method that requires very precise construction management and surveying.

Meanwhile, next-generation surveying solutions that leverage smart technologies such as RTK (Real-Time Kinematic) positioning, AR (Augmented Reality), and cloud integration have recently appeared. Among them, LRTK is attracting attention. Composed of a smartphone, a compact high-precision GNSS receiver, and a dedicated app, LRTK is a surveying DX service that combines centimeter-level RTK positioning accuracy, the ease of use on a smartphone, intuitive AR coordinate guidance, and cloud-synchronized data sharing. This ease—allowing site managers and surveyors to operate the system with one smartphone each—makes it particularly powerful on complex construction sites like those using the reverse construction method.

This article explains, primarily for general contractor construction managers and surveyors, how the fusion of "reverse construction method × smart technology" is transforming construction management. We will outline the reverse construction method and its conventional challenges, and then look concretely at how smart surveying technologies such as LRTK overcome those challenges. We will also consider improvements in on-site efficiency and accuracy, and the potential for construction management DX (digital transformation) looking ahead.

What is the Reverse Construction Method? Benefits and Construction Management Challenges

First, let’s organize the basics of the "reverse construction method." This special construction method is used for buildings with basement floors and is characterized by constructing underground structures in the opposite order to the usual sequence. In a typical underground construction (the conventional method), the site is excavated and all basement portions below the ground surface are completed before moving on to the above-ground construction. In contrast, the reverse construction method first constructs the above-ground structure (notably the first-floor slab) and uses that structure as support while simultaneously excavating and constructing the underground structure. For example, after pouring the first-floor slab, the slab supports the surrounding retaining walls while the first basement level is excavated and constructed, then the work proceeds to the second basement level, and so on, effectively building downward from the top.

This method has several advantages.

• Shortened construction period: Because above-ground and below-ground works proceed in parallel, the overall schedule can be greatly compressed. This effect is especially significant for large urban projects, where earlier opening and cost reductions due to shorter schedules are important.

• Stable underground construction: Since the upper structure can support the retaining walls during excavation, the stability of the underground space is improved. Compared to conventional methods, it can suppress ground loosening and settlement of surrounding ground, enabling safe deep excavation even on weak ground.

• Reduced temporary works cost: As the upper structure (floor slabs, etc.) can serve as support for retaining works, some of the large number of struts and temporary support materials previously required can be omitted. This can reduce the cost and workload of temporary works in some cases.

On the other hand, the reverse construction method also has construction management challenges and cautions.

• Constraints on the work space: Underground work is carried out in the limited space beneath the upper floors, making the working environment cramped. Access routes for heavy equipment and material handling are restricted, and securing installation space for surveying instruments can be difficult.

• High-precision surveying and layout: Because above-ground and underground structures must be precisely joined later, layout (marking out) of columns and walls requires higher-than-normal accuracy. Tasks to transfer reference points between floors increase during construction, and small surveying errors can lead to misalignment in later stages or rework.

• Complex process management: In addition to parallel above- and below-ground work, the process involves structures mutually supporting one another, so planning and on-site management require advanced judgment. Communication errors between tasks or misunderstandings of design drawings can lead to serious problems.

• High-level construction techniques required: Building the underground structure while using the upper structure as support requires advanced construction techniques different from conventional methods, such as treatment of concrete joints and planning of temporary supports. Careful construction planning and technical review are required on site, and thorough briefing of workers is important.

As described above, while the reverse construction method offers great benefits, it requires meticulous management and technical skill. In particular, the importance of surveying and layout work is high, and these are moments where construction managers and surveyors can demonstrate their expertise. So how can smart technologies play a role on such reverse construction sites? The next chapter looks at solutions provided by smart surveying technologies using LRTK as an example.

On-Site Transformation Brought by Smart Surveying Technology LRTK

Now let’s see what specific solutions the smart surveying tool LRTK offers for the complex environment of reverse construction sites. LRTK is a surveying system that combines high-precision GNSS and a smartphone app, and it strongly supports construction management through features introduced below.

Raising construction accuracy with RTK positioning precision

One of LRTK’s greatest strengths is its centimeter-level RTK positioning. By attaching a dedicated compact GNSS receiver to a smartphone and correcting satellite positioning data with Real-Time Kinematic technology, GPS errors that usually amount to several meters can be reduced to only a few centimeters or less. Because it provides high-precision positioning not only horizontally but also in elevation, it is powerful for managing all kinds of three-dimensional coordinates that are important on reverse construction sites—such as slab elevation control for basement floors and confirmation of installed positions of structural elements.

Conventionally, achieving millimeter-level precision required meticulous measurements with total stations and careful height checks with levels. But with LRTK, site staff can instantly obtain coordinate values of their current position on a smartphone and compare them with planned values on the drawings. For example, when laying out underground columns, using global coordinates (world geodetic system) calculated by LRTK makes it possible to immediately check whether column centers align between above-ground and underground floors. Small positional deviations can be detected early, preventing rework and improving structural accuracy.

Moreover, LRTK supports Japan’s "Michibiki" satellite high-precision positioning service (CLAS), enabling stable positioning even in urban areas with unstable signal environments or in situations where the sky is temporarily obstructed by underground structures. Even in the surveying-challenging spots common to reverse construction, LRTK can continually provide accurate positioning, maintaining the reliability of survey data. The assurance of consistently obtaining high-precision position information is a powerful asset for construction managers.

Ease of smartphone operation enables anyone to survey immediately

Because LRTK is operated via smartphone, its ease of use brings great benefits to the site. Simply attach the dedicated terminal (a compact GNSS unit weighing approximately 100–150 g) to a smartphone and launch the app to prepare for high-precision surveying. No complicated setup or advanced instrument configuration is required, so you can start measuring immediately upon arriving at the site. This is particularly useful for reverse construction sites where work must be well-coordinated within limited time.

Previously, surveyors often had to transport and set up total stations and perform layout tasks as a team. With LRTK, however, construction managers or younger staff can quickly perform surveying alone. The device is lightweight and small enough to fit in a pocket, so it can be carried at all times and taken out whenever needed. For example, if you suddenly need to check the elevation of a certain spot or check the positional relationship between drawings and the site, LRTK allows you to handle it without waiting for a surveying specialist. Having an environment where anyone on site can acquire surveying data leads to reduced waiting time and faster decision-making, giving breathing room to the tight process management required by the reverse construction method.

Also, the fact that the operation interface is unified in a smartphone app makes it easy to learn. Intuitive UI design and clear workflows mean that people without deep IT or surveying-equipment knowledge can master the system in a short time. If surveying tasks that previously relied on veteran staff can be shared across the team, it becomes easier to maintain efficiency even at sites suffering from labor shortages. If LRTK’s spread realizes a “one device per person” surveying DX, it will directly raise overall site productivity.

Intuitive construction checks and layout with AR coordinate guidance

The AR (Augmented Reality) functionality provided by LRTK transforms how layout tasks and construction checks are performed on site. Instead of the conventional method of using plans, measuring tapes, and surveying instruments for marking out and position checks, the LRTK app intuitively guides workers through the smartphone screen. For example, design reference points and structural edge positions can be displayed as markers over the camera view in the LRTK app, allowing workers to immediately see in the real scene “where to drive a pile” or “where the next wall should be constructed.” In reverse construction underground work, marking out locations that cannot be directly observed from upper floors is a challenge, but AR coordinate guidance can project virtual layout lines or pile markers into the field of view, enabling smooth position setting even in confined spaces.

Furthermore, LRTK’s AR features go beyond single-point guidance and can overlay construction imagery using 3D models. By uploading BIM/CIM or other 3D design data to the cloud and displaying them in AR aligned to the site coordinate system on a smartphone, you can compare the design model and current conditions on the spot. For example, before pouring concrete for an underground floor, you can project the completed 3D model onto the site to confirm the positional relationships of structural frames and openings in advance. Sharing the post-completion appearance on site—difficult to grasp from paper drawings—reduces the risk of rework caused by misunderstandings. In meetings with clients or stakeholders, showing a specific completion image via AR makes consensus-building easier and shortens the time spent on explanations.

Thus, AR coordinate guidance helps bridge the gap between the site and design, which is a key to smoothly progressing the complex construction of reverse methods. Visualizing parts previously dependent on intuition or experience with digital data reduces the burden on construction managers and ensures quality. LRTK’s AR features act as a robust support for tomorrow’s smart construction.

Cloud synchronization makes information sharing and record-keeping seamless

LRTK provides a mechanism to immediately synchronize all data collected on site to the cloud. Coordinate values, photos, point cloud data, notes, and more can be uploaded from a smartphone with a single tap, allowing team members in the office or at other locations to view the latest information from the moment measurements are taken. On reverse construction sites, it is critical that multiple stakeholders—such as the above-ground team and the underground team, or construction and design personnel—grasp progress in real time. Cloud synchronization helps close the information gap between the site and the office, creating an environment where everyone can make decisions based on the same data.

For example, if a column position on the first basement level is measured and immediately synced to the cloud, designers in the office can check the coordinates and quickly verify any deviation from the plan. If there is an issue, feedback can be provided right away so corrections can be made on the spot. In addition, accumulated measurement points and point clouds can be viewed on maps and drawings within the LRTK cloud, streamlining confirmation of as-built conditions and preparation of reporting materials. Measurement records that site supervisors previously compiled manually after work hours are now digitally stored automatically, helping to prevent omissions in records and reduce the burden of document preparation.

Moreover, LRTK cloud makes it simple to share data with external parties. If you want to show specific measurement data or a point cloud model to a subcontractor or client, you can select the relevant data in the cloud and issue a sharing URL, allowing the recipient to immediately view it in a 3D viewer via a browser. This avoids installing dedicated software or engaging in cumbersome exchanges, reducing communication costs across the project. Such cloud utilization eliminates time lags in information transmission common to complex works like the reverse construction method and enables fast, unified construction management across site and office.

Conclusion: Construction Management Moves to the Next Generation with Reverse Construction Method × LRTK

We have examined the benefits brought by combining the reverse construction method with smart surveying technologies. By integrating cutting-edge technologies like LRTK with the reverse construction method—which already enables schedule reduction and stable construction—significant improvements can be expected across accuracy, efficiency, and communication. Parts that previously relied on craftsmen’s intuition and experience can be replaced by data-driven management, reducing errors and easing workloads. With the site and office seamlessly connected, project-wide visibility improves and all stakeholders can approach construction with a shared sense of purpose.

In practice, as digital construction continues to advance domestically and internationally, smart surveying systems like LRTK are becoming a new standard for construction management. Their benefits have been reported not only for advanced projects like reverse construction but also for general civil engineering and building works. As keywords like “site DX” and “i-Construction” indicate, the construction industry as a whole is steering toward digital transformation, and there is no reason not to leverage these tools.

If your site will undertake reverse construction, consider adopting LRTK. Because LRTK can be started easily with a smartphone, the barrier to entry is not high even for first-time users. By introducing smart technologies to the site, even in small steps, you will be able to experience their convenience and effectiveness. Why not realize next-generation construction management—opened by reverse construction method × smart technology—on your project?