A New Era of Low-Cost 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 a wide range of applications from construction planning to as-built management. With government-led promotion of i-Construction, the trend of managing sites with 3D data using ICT technologies is accelerating. However, there are also many voices saying, "We want to start 3D surveying, but the specialized equipment is expensive and the barrier is high." In this article, we outline the basics of 3D surveying and the challenges of traditional methods, and introduce LRTK, a noteworthy new surveying approach that enables low-cost surveying anyone can start. Let’s take a closer look at the transformation LRTK brings to construction sites and its benefits.

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

3D surveying refers to methods that acquire targets such as terrain and buildings as three-dimensional coordinate data (length, width, height). From the acquired data, you can create 3D models, contour maps, and cross-sections, enabling a more intuitive and detailed understanding of site conditions. For example, complex terrain that used to be representable only 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 perform non-contact measurements in places people cannot safely enter. Using drone aerial photography or laser scanners makes it possible to survey remotely and safely. In addition, because wide-area data can be captured in a short time, surveying can be completed efficiently with fewer personnel. Traditional manual surveying using transits and levels required multiple people to measure point by point, but advances in 3D surveying technologies have dramatically improved work efficiency.

Traditional 3D surveying methods and their challenges

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

• High equipment and setup costs: High-precision laser scanners and surveying drones can easily cost several million yen just for the hardware. In addition, dedicated software and operator training also incur costs, making it difficult for small to mid-sized sites to adopt them.

• Complex procedures and operations: For drone surveying, permission applications under aviation law and handling weather impacts are required, so you cannot fly anytime, anywhere. Laser scanners also require time-consuming setup and calibration, and covering wide areas often means repeated re-installation.

• Data processing burden: The amount of 3D data obtained is enormous, and point cloud processing and photo analysis demand high-performance computers and specialized knowledge. Rather than using results immediately on site, data are often processed in-house over time, reducing immediacy.

Thus, while traditional 3D surveying offers major benefits, it has also been true that the barriers in terms of “cost,” “ease of use,” and “timeliness” were high. Now, however, new technologies are opening the way to low-cost, easy 3D surveying. A representative of this trend is the approach called LRTK.

The emergence of high-precision surveying technology that’s low-cost to start

The key to achieving 3D surveying without expensive dedicated equipment is the recent advancement of RTK-GNSS technology combined with smartphones. RTK (Real Time Kinematic) is a technique that corrects GNSS (satellite positioning system) data, enabling positioning with errors on the order of centimeters. While ordinary smartphone GPS accuracy is on the order of meters, RTK allows centimeter-level positioning required for civil engineering surveying.

RTK positioning traditionally required expensive dedicated receivers and base stations, but miniaturization and cost reduction have progressed, and external RTK units that can be used with smartphones have emerged. Among these, a notable solution is LRTK. LRTK combines an ultra-compact RTK-GNSS receiver, a smartphone app, and cloud services to enable anyone to easily perform centimeter-accurate surveying. Compared to dedicated equipment, it lowers the adoption barrier and is expected to promote the "democratization of 3D surveying."

What is LRTK? Turning your smartphone into an all-purpose surveying instrument

LRTK is the name of a pocket-sized RTK positioning device and dedicated app developed by a startup originating from Tokyo Institute of Technology. Simply attaching this small receiver to a mobile device like an iPhone or iPad instantly transforms a smartphone into an all-purpose surveying instrument with centimeter-level accuracy.

Specifically, a roughly 125 g, just 13 mm thick RTK-GNSS receiver is mounted on a smartphone-case-style attachment and connected to the phone via Bluetooth or cable. Launch the dedicated app and you can obtain high-precision positioning of your current location with a single button press and without complicated settings. Precision positioning that used to be handled by specialized surveyors is designed to be usable by anyone through intuitive smartphone operation.

With LRTK, the position information obtained includes a variety of coordinate systems such as Japan Plane Rectangular Coordinates, latitude/longitude, and elevation. Metadata such as date/time and positioning accuracy are automatically attached to measured points, eliminating the need for on-site note-taking or manual calculations. Measurement data can be uploaded from the smartphone to the cloud on the spot and shared instantly with colleagues in the office. It is truly a system where \\"you no longer need a notebook on site"\\ as surveying records become digitized and automated.

Furthermore, LRTK is not just for positioning; it includes a variety of measurement functions that integrate with smartphone cameras and sensors. For example, by using built-in iPhone LiDAR (light detection sensor) and cameras, you can scan the surroundings and acquire 3D point cloud data. Point cloud surveying, which used to require a stationary laser scanner, can now be easily performed with just an LRTK device and a smartphone. The acquired point clouds are automatically tagged with high-precision coordinates, so there is no worry about data distortion during scanning.

One of LRTK’s major appeals is its low cost. Without having to equip expensive dedicated machinery, you can start with a smartphone and a relatively inexpensive receiver, significantly reducing initial investment. Pricing is typically a fraction of that of a standard 3D laser scanner, making it affordable enough to consider "one device per person." Carrying a pocket-sized device and taking measurements whenever needed—LRTK enables a new on-site style.

How LRTK differs from traditional methods: its advantages

So what exactly makes low-cost surveying technologies like LRTK superior to traditional 3D surveying? Here are the main points.

• Dramatically lower upfront cost: Traditional laser scanners and dedicated surveying equipment were costly, but LRTK requires only adding a small device to a smartphone you already own, so initial investment is minimal. This makes 3D surveying accessible not only to large firms but also to small and medium-sized businesses and individual sites.

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

• Ease of operation: Even without special training, anyone can complete surveys by following the smartphone app prompts and pressing a button. Complex device setup and expert knowledge are unnecessary—intuitive usability for anyone is a major difference from conventional technologies.

• All-in-one multifunctionality: One LRTK unit can handle everything from point coordinate measurement to point cloud scanning, layout staking (setting out), photo-based inspection records, and even AR simulations. Previously, different surveying instruments or tools were needed for each task, but one device serving multiple roles simplifies equipment management.

• Real-time data sharing: Data 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 rapid decision-making.

As shown above, LRTK stands apart from traditional 3D surveying methods in cost, usability, and functionality. Next, let’s look at how it can be used on site and what effects it produces.

LRTK use cases spreading across construction sites

Below are examples of tasks LRTK can accomplish and the effects produced. Imagine how the site changes compared to traditional methods.

• 3D as-built recording and quantity estimation: Scanning site terrain and as-built conditions with LRTK enables quick acquisition of precise 3D point cloud data with global coordinates. Volumetric calculations for fill and cut created by heavy machinery can be automatically computed from those point clouds in the cloud. Quantity management that used to require manual calculation or interpreting drawings can now be completed by simply scanning on site. Point clouds can be overlaid with 3D design models in the cloud for design-vs-as-built comparison.

• Layout staking and installation position measurement: LRTK can streamline setting out building reference lines and checking installation positions. Tasks that once required survey equipment and skilled layout technicians can now be done by specifying target coordinates in the LRTK app, which guides users to each point. Using AR, the app can display virtual stakes or markings on the smartphone screen to enable intuitive layout staking. Comparing drawings with actual positions facilitates prevention of layout mistakes and smoother consensus building among stakeholders.

• Non-contact measurement of hazardous or high locations: For cases like "I want to measure a point on the cliff face where people can’t go" or "I want the elevation of a bolt located high on a bridge," LRTK can solve these with a feature called target-based positioning. By photographing the target with a smartphone camera and calculating direction and distance, coordinates of distant objects can be determined without close approach. This eliminates the need to climb or erect scaffolding, directly improving safety and work efficiency.

• Streamlining photo records and reporting: LRTK is also powerful for managing construction record photos. Photos taken via LRTK are automatically tagged with exact coordinates and camera orientation. There is no need to write notes on paper drawings saying "photo taken around here." Photos are plotted on a cloud map and instantly shared with all stakeholders. Shooting date/time and notes are linked and saved, allowing reports to be automatically generated with a single click, greatly reducing administrative work.

As these examples show, using LRTK makes site measurement and surveying much faster and easier compared to conventional methods. Being able to measure as needed and make quick decisions and actions 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 specialist technicians and expensive equipment, the arrival of LRTK is changing the landscape. With LRTK’s low-cost entry, even non-expert staff can obtain and utilize high-precision surveying data across a variety of on-site situations. As a simple surveying tool anyone can use, LRTK holds the key to digitalization and DX advancement in construction.

The new era of 3D surveying has already begun. If you feel "We’d like to introduce 3D surveying at our site, but it seems difficult," why not start with a simple LRTK survey? Measuring with a smartphone pulled from your pocket converts the site scenery into digital data—once you experience that ease, you may never go back to traditional surveying. Bring revolutionary change to your site with this cutting-edge, low-cost surveying method.