Centimeter-level accuracy (inch-level accuracy) is the keyword for improving on-site efficiency and quality. High-precision positioning that once required specialized surveying equipment and expert skills can now be easily introduced via subscription services for RTK positioning. On construction and surveying sites, obtaining accurate position information in real time can speed up work and reduce human errors.

This article explains RTK positioning from the basics, the benefits of subscription services, the implementation steps and on-site use cases, and even smartphone surveying using the noteworthy LRTK technology, all explained from a field perspective. If you are considering operational improvements, please use this as a reference.

Table of Contents

• Basics and necessity of RTK positioning

• Features and implementation benefits of subscription-based RTK

• Implementation flow and required components

• On-site use cases

• Cost-effectiveness and differences from traditional methods

• Smartphone surveying and point cloud accuracy improvement using LRTK

• FAQ (questions about RTK positioning, subscriptions, and LRTK)

Basics and necessity of RTK positioning

RTK positioning (Real Time Kinematic positioning) is a positioning technology that uses GNSS satellites to determine position in real time with errors down to a few centimeters (a few in). General GPS positioning can have errors of several meters, but RTK dramatically reduces positioning errors by applying correction information from a base station to the rover. This enables accuracy within a few centimeters (a few in) horizontally, allowing real-time acquisition of position information robust enough for infrastructure construction and precision surveying.

Why is centimeter-level accuracy needed on site? For example, if the installed position of a structure in civil engineering shifts by a few centimeters (a few in), it can affect the final product's quality and safety. In infrastructure inspections, it is required to detect and grasp minute ground subsidence or structural displacement of only a few centimeters (a few in). These demands, which cannot be met by the traditional meter-level positioning accuracy, make centimeter-level high-precision positioning indispensable.

With RTK positioning, initial layout tasks (staking out or pile positioning) can be done accurately, reducing rework and additional touch-up work. As a result, overall construction quality and efficiency improve, and RTK adoption has expanded across sites from major general contractors to small and medium-sized construction companies.

Furthermore, the Ministry of Land, Infrastructure, Transport and Tourism's push for construction DX (digital transformation) and the i-Construction trend have increased attention on improving on-site positioning accuracy. ICT construction machines such as machine guidance/machine control use GNSS receivers mounted on construction equipment to grasp the blade position and elevation in real time, and RTK-GNSS supports that high-precision positioning. With high-precision position information, heavy equipment operators can always confirm their working height from the cab and perform construction while preventing human error and dramatically improving work efficiency. In this way, RTK positioning is a key that brings innovation to the field in various areas such as construction management, surveying, and maintenance.

Features and implementation benefits of subscription-based RTK

Subscription-based RTK is a model that provides the correction information service and equipment necessary for RTK positioning as a monthly service rather than a one-time purchase. By leveraging cloud-based RTK correction services, users can achieve centimeter-level positioning (inch-level positioning) across Japan without installing their own base stations. This is possible because service providers build GNSS reference station networks nationwide and distribute correction data in real time over the internet. Users only need a GNSS receiver as a rover to start high-precision positioning immediately on site.

The biggest advantage of subscription-based RTK is the low barrier to entry. Purchasing and installing high-precision GNSS equipment from scratch required significant initial investment for antennas, high-performance receivers, radio equipment, and more. In contrast, subscription models allow users to reduce upfront costs and use the service when needed. For example, by paying a monthly fee to join the correction service, you can start positioning that day using your receiver and smartphone. Even without funds to buy all equipment, subscription services let you contract only for the necessary period, making it easy for small-scale sites and short-term projects to adopt.

Also attractive are the updatability and maintainability unique to cloud services. Correction networks and software are constantly updated by the provider, so users always enjoy the latest positioning environment. As satellite navigation systems expand (new satellites or signal improvements), the service provider handles those updates, and users automatically benefit from improved accuracy. If hardware is provided via rental, it's easier to receive replacement units in case of failure or future device upgrades. In other words, subscription RTK offers high on-site flexibility, allowing you to use high-precision positioning resources as much as needed, when needed.

Moreover, the barrier in terms of personnel and skills is lowered. Systems that link with smartphones and tablets rather than dedicated devices are increasing, enabling intuitive app operation for positioning and data management. Not only specialized surveying technicians but also construction managers and workers themselves can increasingly handle RTK equipment. This ease of use by anyone on site is likely to significantly change future construction styles.

Implementation flow and required components

Implementing subscription-based RTK services is easier than you might imagine. Below is a summary of the typical implementation steps and required components.

• Prepare a compatible GNSS receiver: First, prepare a GNSS receiver (rover) that supports centimeter-level positioning (inch-level positioning). Recently, various compact and portable receivers have emerged, including types that can be attached to smartphones or tablets. Be sure to choose a model that can receive RTK correction information (multi-band GNSS support is recommended).

• Prepare positioning apps/software: Install the dedicated positioning app or software on the smartphone/tablet used with the GNSS receiver. In many cases, receiver manufacturers or service providers offer free apps. This app handles connection settings to the correction service, displays positioning results, and saves data.

• Subscribe and configure the correction service: Contract with the subscription RTK correction information service and obtain a user account (ID and password). This is similar to registering for a network RTK service (so-called VRS services). After contracting, enter the issued ID into the positioning app mentioned above. Since correction data is distributed via protocols such as Ntrip, configuration is usually as simple as inputting the ID and password.

• Secure a communications environment: Internet connectivity is required at the site to receive correction information. Prepare mobile data (4G/5G) on a smartphone or a pocket Wi‑Fi so the positioning app can access the correction server online. In mountainous areas with no cellular signal, consider using satellite augmentation signals (for example, CLAS from quasi-zenith satellites) as described later, or temporarily operate the rover in standalone positioning mode.

• Start positioning and operation: Install or carry the receiver on site and start receiving correction information in the positioning app. RTK initialization (FIX solution) usually occurs within tens of seconds, enabling high-precision positioning. Check coordinates and accuracy indicators on the app, and when ready, proceed with surveying or construction. The coordinates of collected points can be saved in the app or synced to the cloud, allowing you to check results on the spot.

As described above, having three components—receiver, communications environment, and correction service—enables immediate cm-level positioning (inch-level positioning). Device setup is simple, and first-time users can master it in a short time with manuals or support. Because you don’t have to worry about “how to set up a base station” or “radio frequencies,” the introduction barrier is significantly lower than traditional methods.

On-site use cases

Subscription-based RTK demonstrates its power across various tasks. Here are representative use cases on construction and surveying sites.

• As-built management: When measuring the as-built shape and dimensions after construction, RTK enables quick and high-precision field surveying. Traditionally, total stations often required two-person teams, but with an RTK rover, one person can walk and collect many survey points in a short time. You can check pavement thickness and fill heights in real time and immediately adjust shortages or excesses on-site, enabling a PDCA cycle right on site.

• Pile driving and staking out: RTK is also active in positioning foundation pile locations and building layout tasks. A worker holding a GNSS rover can stand at the designated coordinates and follow guidance from a guidance app—such as “5 cm east, 2 cm north”—to mark or set piles accurately. Even on large sites, the effort to repeatedly set up rectangles for reference is reduced, enabling efficient positioning work by a single person. (「あと東に 5 cm (2.0 in)、北に 2 cm (0.8 in)」)

• Photogrammetry: In photogrammetry using drones or DSLR cameras, the conventional method required many ground control points (marked known-coordinate points). With RTK, the drone itself or the camera shooting position can be recorded with high accuracy, drastically reducing the number of ground control points needed. For example, aerial photography using an RTK-equipped drone produces orthoimages and 3D point clouds with spatial coordinates ensured to centimeter-level accuracy (inch-level accuracy). This speeds up drawing creation and earthwork volume calculations, directly improving overall surveying efficiency.

• Drone point clouds and 3D surveying: Using RTK-capable drones provides high-precision 3D survey data. For wide-area topographic surveys or structure inspections, conventional approaches required ground-based laser scanners or many targets. However, point clouds from RTK-equipped drones can meet required accuracy without additional equipment. The created 3D point cloud models are useful for as-built understanding, displacement detection, and construction planning.

• Buried object surveys: When using ground-penetrating radar to locate underground pipes or cables, recording and marking the center position with RTK helps prevent accidental hits during excavation. Because the drawn coordinates match the on-site markings with high accuracy, you can plan safe excavation work without backtracking. In one case, using RTK for marking after subsurface surveys resulted in zero pipe damage during heavy-equipment excavation.

• Disaster response: High-precision positioning supports rapid response at landslide or earthquake damage sites. By drone-imaging a disaster site and quickly creating an RTK-standard ortho map, you can accurately grasp the damage extent and formulate recovery plans. Also, if terrain or structures have deformed and existing map coordinates are unreliable, RTK surveying can re-acquire accurate on-site coordinate data, enabling decision-making based on reliable information.

By adopting subscription-based RTK, surveying, construction, inspection, and disaster response can all be streamlined and enhanced. High-precision position information accurately visualizes site conditions, reduces unnecessary rework, and can simultaneously improve safety and productivity.

Cost-effectiveness and differences from traditional methods

The cost-effectiveness of subscription-based RTK is very high compared with traditional approaches. Below are the main differences summarized.

• Initial cost: Traditionally, introducing RTK required purchasing two GNSS receivers (base and rover), radio equipment, dedicated software, and other expensive gear. With subscription models, you don’t need to procure these in-house, and required equipment is minimized. Some services also offer receiver rentals, significantly compressing initial investment.

• Operating cost: With owned equipment, continuous burdens such as maintenance, periodic calibration, and repair costs occur. For network RTK services, the provider bears the costs of maintaining the correction network and reference stations, so users have no extra expenses beyond the monthly fee. You can also contract only for the required period, avoiding idle assets.

• Labor costs and schedule: High-precision positioning reduces time spent on manual work and surveying. For example, tasks that previously required two people for setting out can now be done by one, and fewer survey points may halve on-site surveying days. This leads to reductions in labor costs and construction schedules, improving cost performance.

• Accuracy and quality: Parts of traditional methods that relied on craftsmen’s intuition and experience can be numerically managed with high-precision equipment, reducing variability. Deviation in as-built results decreases, cutting costs for rework. The final outputs (drawings and 3D models) are also more accurate, positively affecting future maintenance and asset management.

• Prevention of opportunity loss: As high-precision positioning and digital construction become standardized, early adopters can maintain competitiveness. Delayed adoption risks falling behind competitors in efficiency and quality. Subscription models let you try the latest technologies with minimal burden, preventing missed opportunities and offering strong cost-effectiveness.

Given the above, subscription-based RTK is a “cheap, easy, highly effective” solution. Of course, the optimal implementation varies by site scale and use, but it is certainly worth trying at least once.

Smartphone surveying and point cloud accuracy improvement using LRTK

The recently emerged technology called LRTK further expands the possibilities of RTK positioning. LRTK is a solution that dramatically simplifies surveying work by combining smartphones with specialized small GNSS receivers. By attaching a dedicated ultra-compact receiver to a smartphone and performing positioning and data processing via a smartphone app, one could say “the smartphone itself becomes surveying equipment.”

With LRTK, smartphone surveying becomes a reality. For example, linking the LiDAR scanner or camera built into the latest smartphones with RTK positioning allows you to acquire 3D point clouds simply by walking around. Places that previously could only be measured with laser scanners or drones (such as the underside of bridge girders or under trees) can now be point-cloud mapped in detail by a person walking with a smartphone. Moreover, the acquired data are immediately tagged with absolute coordinates, eliminating the need to place reference points afterward and align data.

The accuracy improvement of point clouds and photographic data obtained by smartphone surveying is also notable. RTK dramatically increases the coordinate accuracy of each point, enabling precise geotagging of photos and giving absolute accuracy to scanned point clouds. Photos taken on site can accurately show on a GIS map exactly where and in what direction they were taken, allowing office staff to grasp site conditions precisely from shared photos. In addition, you can instantly calculate volumes from high-precision point clouds or measure arbitrary cross-sections, speeding up construction management and as-built confirmation.

LRTK’s strength is offering these capabilities in a simple form anyone can use. There are no complicated wirings or difficult operations—just a smartphone, a small receiver, and an app to complete advanced surveying on site. Devices are rugged enough to withstand rain and dusty environments, so they can be confidently used in harsh civil engineering sites. They also support both satellite and cellular communications, flexibly switching to satellite augmentation signals when outside radio coverage. With the advent of LRTK, the era of “one smartphone surveying device per person” is approaching.

FAQ (questions about RTK positioning, subscriptions, and LRTK)

Q. What is the difference between RTK positioning and normal GPS positioning? A. Standalone GPS (GNSS) positioning typically has errors of several meters, while RTK positioning uses correction information from a base station to reduce errors to a few centimeters (a few in). The major difference is that RTK achieves high accuracy in real time, making it powerful for precise applications like construction and surveying.

Q. What is needed to start subscription-based RTK? A. Basically, (1) an RTK-capable GNSS receiver, (2) a device such as a smartphone or tablet with a positioning app, and (3) subscription to a correction information service are required. With an internet connection at the site, you can start centimeter-level positioning (inch-level positioning) immediately.

Q. Can you really survey with just a smartphone? A. You need to attach a dedicated small GNSS receiver, but yes, it is possible. Modern smartphones have high-performance sensors and cameras, and with technologies like LRTK, a smartphone becomes a high-precision surveying device. Intuitive operation lets non-experts perform point cloud and photo surveying easily.

Q. What if the correction service signal does not reach the site? A. In areas without cellular coverage such as mountainous regions or underground, you can use Japan’s Quasi-Zenith Satellite System (QZSS, “Michibiki”) centimeter-level augmentation service (CLAS). A CLAS-compatible receiver can receive correction information from satellites without using the internet. Alternatively, temporarily setting up a base station for local RTK operation is an option; choose the optimal service according to your work area.

Q. I feel the monthly fee is a waste… A. In many cases, subscription fees return value beyond their cost. Considering reduced rework and shortened work time, savings in labor costs, and accident prevention from improved safety, you can often recover the cost. The flexibility to contract only for the required period also reduces the risk of wasteful spending.

This has provided a comprehensive explanation of subscription-based RTK utilization. The efficiency gains from centimeter-level position information (inch-level position information) are immeasurable. The implementation barrier has dropped significantly compared to the past, so if you are interested, consider trying a subscription-based RTK solution. Once you experience its effects on site, it will likely lead to the next action.