A New Era of Cost-Effective 3D Surveying: Why LRTK Is Changing Construction Sites

In recent years, 3D surveying has attracted significant attention in the construction industry. Because it can accurately digitize the three-dimensional shapes of terrain and structures that conventional planar surveying could not capture, its use has been expanding across various stages from construction planning to as-built management. Government-led promotion of i-Construction (i-Construction) has also accelerated the trend of managing sites with ICT technology using 3D data. However, there are still many voices saying, “We want to start 3D surveying, but the specialized equipment is expensive and the barrier is high.” This article organizes the basics of 3D surveying and the challenges of conventional methods, and introduces LRTK, a noteworthy new-era surveying method that anyone can start using at low cost. Let’s take a closer look at the transformation LRTK brings to construction sites and its advantages.

What is 3D surveying? How it differs from conventional surveying

3D surveying (3D measurement) is a surveying method that acquires targets such as terrain and structures as three-dimensional (length, width, height) coordinate data. From the acquired data, you can create three-dimensional models, contour lines, and cross-sections, allowing site conditions to be understood more intuitively and in greater detail. For example, complex terrain that could previously only be represented by plans or elevation numbers can be recorded “as-is” as point cloud data (a collection of many measurement points) with 3D surveying.

The biggest feature of 3D surveying is that it can measure non-contact in places where people cannot directly enter or where it is dangerous. By using drone aerial photography or laser scanner measurements, surveying can be done safely from a distance. Also, because wide-area data can be acquired in a short time, it is advantageous that surveying can be completed efficiently with a small number of people. With manual surveying using transit instruments or levels in the past, multiple people were required to measure point by point, but advances in 3D surveying technology have dramatically improved efficiency.

Conventional 3D surveying methods and their challenges

So far, the main methods for realizing 3D surveying have generally been aerial photogrammetry (drone photogrammetry) and 3D laser scanners. Each has strengths such as covering wide areas or acquiring high-density point clouds, but they also had the following challenges.

• High equipment and introduction costs: High-precision laser scanners and surveying drones can easily cost several million yen for the equipment itself. Additionally, dedicated software and operator training incur further expenses, making it difficult for small and medium-sized sites to adopt them.

• Complex procedures and operation: For drone surveying, permission applications under aviation law and dealing with weather impacts are required, so you cannot always fly wherever and whenever you want. Laser scanners also require time-consuming setup and calibration, and to measure wide areas they often need to be reinstalled repeatedly.

• Data processing burden: The amount of 3D data obtained is enormous, and point cloud processing and photo analysis require high-performance computers and specialized knowledge. Rather than being able to use results immediately on site, in many cases analysis is done in the office over time, which lacks immediacy.

Thus, while conventional 3D surveying offers great benefits, it is also true that the “cost,” “ease of use,” and “immediacy” were significant barriers. Now, however, new technologies are opening the way to low-cost and simple 3D surveying. A symbol of this shift is an approach called LRTK.

Emergence of high-precision surveying technology that can be started at low cost

The key to achieving 3D surveying without expensive dedicated equipment is the recently developed RTK-GNSS technology and the use of smartphones. RTK (Real Time Kinematic) is a technology that corrects GNSS (satellite positioning system) positioning information, enabling positioning with errors of several centimeters (cm level accuracy (half-inch accuracy)). Normally, smartphone GPS accuracy is on the order of several meters, but RTK makes centimeter-level positioning suitable for civil engineering possible.

Until now, RTK positioning required dedicated expensive receivers and base stations, but as the technology has miniaturized and become less expensive, external RTK devices that can be used with smartphones have appeared. One solution attracting attention is LRTK. LRTK combines an ultra-compact RTK-GNSS receiver, a smartphone app, and cloud services to enable anyone to easily perform surveying with centimeter-level accuracy (cm level accuracy (half-inch accuracy)). Compared to dedicated equipment, its introduction hurdle is low, and it is expected to promote the “democratization of 3D surveying.”

What is LRTK? Turning a smartphone into an all-purpose surveying device

LRTK (Eru Aru Tee Kee) is the name of a pocket-sized RTK positioning device and dedicated app developed by a startup originating from the Tokyo Institute of Technology. By attaching this small receiver to a mobile device such as an iPhone or iPad, the smartphone quickly transforms into an all-purpose surveying instrument with centimeter-level accuracy.

Specifically, an RTK-GNSS receiver weighing approximately 125 g and with a thickness of just 13 mm (0.51 in) is attached to a smartphone-case-style attachment and connected to the phone via Bluetooth or cable. By launching the dedicated app, you can position your current location with high accuracy at the touch of a button without complex settings. Precision positioning that used to be handled by professional surveyors has been designed so that anyone can operate it with intuitive smartphone controls.

When using LRTK, the position information obtained includes a variety of formats such as Japan Plane Rectangular Coordinates, latitude and longitude, and elevation. Metadata such as the date/time and positioning accuracy are automatically attached to the recorded measurement points, eliminating the need to take notes or perform calculations on site. Measurement data can be uploaded from the smartphone to the cloud on the spot and immediately shared with colleagues in the office. It is exactly “to the extent that writing tools on site become unnecessary”, a system that advances the digitization and automation of survey records.

Moreover, LRTK is not only for measuring positions; it also features a variety of measurement functions linked to the smartphone’s camera and sensors. For example, by utilizing the iPhone’s built-in LiDAR (light detection sensor) or camera, it is possible to scan the surroundings and acquire 3D point cloud data. Point cloud surveying, which previously required stationary laser scanners, can now be carried out easily with only an LRTK device and a smartphone. Since high-precision coordinates are automatically added to the acquired point clouds, there is no need to worry about data distortion during scanning.

Being low-cost is also a major attraction of LRTK. Without preparing expensive dedicated equipment, you can get started with just a smartphone and a relatively inexpensive receiver, significantly reducing initial investment. Its price is a fraction of that of typical 3D laser scanners, making it affordable enough to equip one per person. Carrying a pocket-sized device and taking it out for measurements whenever needed—LRTK enables this new style of on-site work.

Differences from conventional methods: Where LRTK excels

So, in concrete terms, what advantages do low-cost surveying technologies like LRTK have over conventional 3D surveying? Here are the main points.

• Dramatically lower introduction cost: While conventional laser scanners and surveying-dedicated equipment were expensive, LRTK only requires adding a small device to your existing smartphone, so the initial investment is very small. This makes it easier not only for large companies but also for small and medium-sized enterprises and even individual sites to engage in 3D surveying.

• Portability and mobility: There is no need to carry heavy tripods or large equipment; with pocket-sized LRTK it is easy to walk around the site to take measurements. It is useful in remote mountainous areas and disaster sites where large equipment cannot be brought in. It can also be attached to a helmet for hands-free surveying as needed, expanding the range of tasks.

• Ease of operation: Even those without special training as survey technicians can complete measurements by following on-screen prompts and pressing buttons on the smartphone app. Complex equipment settings and specialized knowledge are unnecessary, and the intuitive usability that anyone can handle is a major difference from conventional technology.

• All-in-one multifunctionality: One LRTK unit can handle everything from point coordinate measurement to point cloud scanning, layout staking, photographic investigation records, and even AR-based simulations. Whereas previously separate surveying instruments and tools were required for different purposes, one device performing multiple roles simplifies equipment management.

• Real-time data sharing: Measurements can be uploaded to the cloud on the spot and shared with the office or other companies, so there is almost no waiting time for results. Point clouds that used to take time to process can be visualized and measured instantly in the cloud with LRTK, enabling prompt decision-making.

As described above, LRTK stands apart from conventional 3D surveying methods in terms of cost, usability, and functionality. Now, let’s look at concrete on-site use cases and the effects it brings.

LRTK use cases spreading on construction sites

Here are examples of tasks LRTK can accomplish and the benefits. Compare with conventional methods to imagine how the site will change.

• 3D record of existing conditions and quantity measurement: Scanning the site terrain and as-built with LRTK allows you to quickly acquire precise 3D point cloud data with global coordinates. Volume calculations for fill and cut created by heavy equipment can be automatically computed from that point cloud in the cloud. Earthwork quantity management that previously took time with manual calculations or plan reading can now be completed by simply scanning on site. Point clouds can be compared by overlaying them with 3D models in the cloud, making them useful for checking differences from the design model.

• Layout staking and installation position measurement: LRTK can reduce labor for establishing building reference lines and confirming installation positions of structures. These tasks previously required surveying instruments and skilled staking workers, but if you specify target coordinates in the LRTK app it will guide you to the point. Using the AR function, you can display virtual stakes or markings on the smartphone screen for intuitive layout staking. Being able to compare drawings and actual positions visually helps prevent layout mistakes and facilitates consensus among stakeholders.

• Non-contact measurement of hazardous or high locations: When you want to measure a point on a cliff face that people cannot approach, or determine the height of a bolt on a high bridge location, LRTK can solve the problem with a feature called “subject positioning.” By photographing the target with the smartphone camera and calculating its direction and distance, coordinates of a distant object can be derived non-contact. This avoids the need to climb to high places or set up scaffolding, directly improving safety and work efficiency.

• Efficiency in photographic records and reporting: LRTK is also powerful for managing construction record photos. Photos taken via LRTK are automatically tagged with the precise coordinates and camera orientation of the shooting location. There is no longer any need to annotate paper drawings with “photo taken around here.” Photos are plotted on a map in the cloud and shared instantly with all stakeholders. Shooting date/time and notes are also linked and saved, enabling report generation with the push of a button and significantly reducing clerical work.

As these examples show, using LRTK makes surveying and measurement tasks on site far faster and easier than conventional methods. Being able to measure as needed and quickly make decisions and proceed with construction based on those results will undoubtedly improve on-site productivity and quality.

Conclusion: Simple 3D surveying anyone can do with LRTK

Where once 3D surveying required specialists and expensive equipment, the situation is already starting to change dramatically with the advent of LRTK. With the low-cost introduction possible with LRTK, even non-expert users can obtain and utilize high-precision survey data in all kinds of on-site situations. In the digitalization and DX promotion of construction sites, LRTK as a simple surveying tool anyone can use can be said to hold the key to the new era.

The new era of 3D surveying has already begun. If you feel, “We want to adopt 3D surveying at our site but it seems difficult,” why not start by trying simple surveying with LRTK? Just measure with the smartphone you pull from your pocket, and the site scenery will instantly become digital data—once you experience that ease, you may find it hard to return to conventional surveying. Bring innovative change to your site with this cutting-edge, low-cost surveying method.