Not Just Drone Surveying! Next-Generation 3D Construction Realized with LRTK

Today, efforts to use digital information such as 3D design data and point clouds on construction sites are increasing, and the way we carry out construction is changing significantly. In recent years, drone surveying has become widely adopted on construction sites and is attracting attention as an efficient method for acquiring 3D data. However, next-generation 3D construction (construction utilizing 3D data) is not achieved by drones alone. As a new technology that can further advance on-site DX, a high-precision positioning system that can work with smartphones, [LRTK](https://www.lrtk.lefixea.com), has emerged. This article summarizes the overview and challenges of drone surveying and introduces the diverse functions and use cases that LRTK offers. We explain in detail the possibilities of new 3D construction that does not rely solely on drones and the benefits of introducing LRTK.

Overview, Benefits, and Challenges of Drone Surveying

Drone surveying is a surveying method that mounts cameras or LiDAR (laser scanners) on small unmanned aerial vehicles (drones) to capture photos and laser point clouds of a site from above. As part of the i-Construction initiative, its full-scale introduction progressed around 2016, and it has now become indispensable for quality control of construction shapes and earthwork volume calculations in infrastructure projects. Drone surveying, which can acquire 3D data over an area from the air, is overwhelmingly more efficient than traditional ground surveys and is being used increasingly across many sites.

Drone surveying has the following advantages:

• Because it captures wide areas from the air at once, it can obtain high-density survey data in much less time than traditional methods

• Non-contact measurement makes it possible to safely measure steep slopes or hazardous areas where workers cannot enter

• Accurate 3D models and drawings can be created from captured photos and point cloud data, enabling use in as-built management and construction planning

• It can be operated with a small crew, contributing to labor savings and time reduction compared to traditional ground surveys

On the other hand, there are also the following challenges in using drones:

• Due to regulations, they may not be usable in areas where flights are restricted, such as urban districts or around airports

• They cannot fly in rain or strong winds and are subject to weather conditions

• In confined sites or indoor spaces, takeoff/landing and GPS reception can be difficult, limiting effectiveness

• Operators need skills and flight permissions, so operation requires specialized knowledge and prior preparation

Diverse Approaches in 3D Construction

Besides drone surveying, various initiatives that utilize 3D data and digital technologies in construction sites are progressing. Depending on the purpose and site conditions, combining several methods enables efficient construction management. Here are some main approaches:

• Machine guidance/machine control with ICT construction equipment: A method that equips heavy machinery with GPS and 3D design data to automatically control blade height and slope during operation. This allows high-precision construction independent of the operator's skill level.

• Terrestrial laser scanners and mobile mapping: Methods that use tripod-mounted laser scanners or vehicle-mounted LiDAR to measure existing conditions as point clouds. They can capture millimeter-level precise 3D shapes and are used for detailed measurements of structures and as-built drawing creation.

• 3D positioning using GNSS surveying and total stations: Surveying instruments using satellite positioning (RTK-GNSS) or electronic distance measurement are used to stake out positions or inspect as-built conditions according to design coordinates. These are traditional core methods, but high-precision work requires skilled technicians.

• Use of AR technology: Using tablets or smart glasses to overlay design models and drawing information onto the actual site view. This is effective for sharing the finished image and preventing construction errors and has been gaining attention recently.

Strengths of LRTK as an Alternative and Complementary Solution

LRTK is a new solution developed to make surveying and construction management on-site easier while complementing the various methods described above. LRTK, which is used by attaching a small high-precision GNSS receiver (RTK-capable) to a smartphone or tablet, combines centimeter-level positioning accuracy with the convenience of mobile devices. LRTK devices are compact, weighing only a few hundred grams and fitting in the palm of your hand, with the antenna and battery integrated. Therefore, there is no need to carry bulky equipment, and it is easy to work while walking around the site. Unlike drones that capture data from the air, LRTK enables people to directly walk the site and acquire 3D data, making it powerful in environments where aerial photography is difficult. In addition, the acquired data can be shared and used instantly in the cloud, allowing the previously separate processes of "surveying" and "construction management" to be seamlessly connected with just a smartphone—another major advantage.

In other words, LRTK is a means to complement aerial surveying by drones from the ground, and by using both as appropriate, there are no blind spots in site data acquisition. For example, on a large land development site you can use a drone to capture an overall terrain overview and use LRTK to acquire point clouds for detailed areas or indoor work. With LRTK filling in situations where drones were previously difficult to use, the scope of 3D data utilization will expand further.

Main Functions of LRTK and Concrete Use Cases

• High-precision 3D point cloud scanning: Simply walk around the site holding your smartphone to scan surrounding terrain and structures with LiDAR or a camera and obtain high-density point cloud data. Since RTK positioning from the LRTK device assigns absolute coordinates to each point, the acquired point cloud can be used directly overlaid on map coordinate systems. For example, if slopes or foundations are scanned with LRTK, you can measure dimensions, areas, and volumes on the spot without returning to the office. As-built measurements that were traditionally outsourced to specialists can be quickly carried out by the site staff themselves using LRTK.

• Design visualization with AR display: Using the AR function of the LRTK app, pre-prepared 3D design models or drawing data can be overlaid on the actual site view. Because high-precision alignment is possible, the models are fixed at the correct position and height in real scale and will not drift as you move around. This enables intuitive sharing of the finished image and on-site checks during construction. For example, before excavation you can display models of underground utilities in AR to identify the location of invisible hazards, or overlay the design model during structural work to check the finished quality on the spot. Information that was hard to visualize on paper drawings can be communicated at a glance by overlaying models on the real scene.

• Coordinate guidance (stakeout): LRTK also has a navigation function that guides users to target coordinate points. Arrows and distance information are displayed on the smartphone screen, and it provides real-time guidance as you approach the specified X, Y, Z coordinates. Tasks like staking out or setting batter boards that were traditionally done by surveyors with a total station can be completed by anyone alone in a short time using this function. Even existing control points buried under vegetation or snow that are hard to find by sight can be pinpointed by LRTK if the coordinates are known.

• As-built management and data sharing: Point cloud data and photos acquired by LRTK can be uploaded to the cloud and checked or used immediately from office PCs. This allows on-site acquired as-built data to be shared with stakeholders the same day, aiding quality checks and progress quantity reporting. Advanced analyses such as overlaying design data and existing point clouds to color-code deviations or calculating cut-and-fill volume differences to determine shortages/excesses are also automated. Measurements and inspections that used to require all hands on deck after completion can be greatly streamlined and accelerated by introducing LRTK.

LRTK Use Cases Where Drones Are Difficult to Use

• Confined or small-scale sites: When the construction area is extremely narrow or surrounded by many obstacles, securing space and preparing for drone flights can become more cumbersome. With LRTK, required 3D surveying can be completed just by a staff member walking the site. There is no need for takeoff space or wide airspace for safe flight. The ease of responding to simple surveys for minor land rearrangements or indoor work is a major advantage.

• Urban sites: Drone flights in urban construction sites face strict constraints. Obtaining flight permissions in densely populated areas, privacy concerns, and radio interference from surrounding buildings can present high hurdles. LRTK performs measurements from the ground, so it is not affected by these aviation law restrictions and can acquire 3D data. In fact, for urban roadworks and similar projects where drone-based as-built measurement was previously abandoned, introduction of LRTK has enabled routine point cloud recording.

• Indoor and underground spaces: In indoor work and tunnel or underground structures where GPS does not reach, drones cannot operate properly. However, LRTK can utilize smartphone AR technologies and various sensors to perform relative positioning and 3D scanning even where satellite signals are unavailable. For interior piping and equipment installation, LRTK can scan indoor spaces and assist in as-built verification. Indoor construction management, which traditionally relied on manual measurements and comparisons with drawings, can be significantly streamlined by introducing LRTK.

• Disaster and emergency sites: Speed is required to grasp conditions immediately after earthquakes or landslides. While drones are useful, they may not be deployable when weather is unstable or flights are prohibited. With LRTK, personnel can go to the site and begin measurements immediately even in such situations. It can operate in standalone mode when communications infrastructure is down, allowing rapid surveying of evacuation shelters or locations for temporary roads. LRTK’s mobility and responsiveness make it a reliable tool for disaster response and accident scene recording. In fact, some local governments have reported cases where they recorded 3D data of landslide damage with LRTK and used it to plan restoration work.

Benefits of Implementing LRTK: One-person Surveying, Rapid Response, and Labor Savings

Introducing LRTK on site brings various benefits in terms of manpower and time. The following three points in particular will greatly contribute to productivity improvements on construction sites:

• Realizing one-person surveying: With LRTK, surveying work that previously required multiple people can be completed by one person. For example, total station surveys required two-person teams (surveyor and staff), but with LRTK a single site staff member can handle everything from point cloud capture to drawing. LRTK, which supports one-person operation, is a powerful assistant for small-scale projects where allocating personnel is difficult or where surveys must be completed within limited working hours.

• Rapid on-site response: The convenience of being able to measure immediately without bringing dedicated equipment or planning a drone flight is another attraction. LRTK is portable and easy to set up, so it can respond on the spot to unexpected measurement needs. When you need to "measure that spot right away," you can start the smartphone and LRTK device and complete point cloud acquisition in minutes. Survey results can be shared to the cloud immediately, speeding up communication between the site and the office.

• Labor savings and cost reduction: Because site staff can perform measurements without relying on skilled operators, outsourcing and labor costs can be reduced. LRTK’s operation is easy to learn, requiring minimal training costs. In the construction industry, which faces serious labor shortages, the effect of LRTK enabling small teams to run sites is significant. Also, since it can handle everything from data acquisition to analysis in one flow, tasks that were previously separate can be consolidated for overall cost reduction.

LRTK Accelerating Site DX and Its Impact on the Construction Industry

Easy-to-use, high-precision 3D technologies like LRTK strongly support DX (digital transformation) at construction sites. Because 3D surveying and construction management, which were once limited to large-scale projects or specialist contractors, can be used routinely by more sites, productivity improvements across the industry are expected. Indeed, combined with trends like the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction and BIM/CIM, the use of digital data on site is becoming an inevitable trend. LRTK has the potential to support site DX across a wide range of companies—from large corporations to small and medium-sized construction firms—as a tool easy to adopt on site.

As site DX progresses, not only will operational efficiency and safety improve, but construction industry workstyles will also benefit. For example, if the labor-intensive surveying work is digitized and streamlined, technicians can spend more time on higher value-added tasks. Also, smart sites that actively use the latest technologies will appear attractive to younger generations, helping with talent acquisition. If the spread of LRTK makes “3D construction” commonplace on sites, it will advance digitalization throughout the construction industry and is expected to contribute to strengthening international competitiveness in the long term.

Conclusion: Easily Start Next-Generation 3D Construction with LRTK

The wave of 3D construction driven by ICT technologies including drones is set to expand further with the advent of LRTK. Even in situations where drone surveying was difficult, anyone can acquire 3D data through simple surveying using LRTK and apply the information obtained on the spot to construction work. Because LRTK can be started simply by attaching a device to a smartphone—without dedicated equipment or large-scale investment—the barriers to site introduction are low.

Sites that have actually introduced LRTK report feedback such as "we can get the data we need in a short time" and "waiting time for surveying has decreased, giving more leeway in construction schedules." It may be a good idea to try it on a small job first to experience its convenience. LRTK is a reliable on-site partner that realistically supports site DX. Rather than relying solely on drone surveying, why not take on next-generation 3D construction using LRTK?