Latest Trends in RTK GNSS: High-Precision Positioning Technology Transforming the Construction and Surveying Industries

Table of Contents

• Introduction

• What RTK GNSS Is and Why It Matters

• Evolution of GNSS Satellites and Measurement Signals

• Latest Trends in Error Correction Services That Support RTK

• Spread and Cost Reduction of High-Precision Positioning Technology

• RTK Adoption Expands on Construction Sites

• Transformation and Efficiency Gains in Surveying Work

• Easy High-Precision Surveying Enabled by LRTK

• FAQ

Introduction

Recently, high-precision positioning technologies that leverage satellite positioning (GNSS) have advanced dramatically. In particular, RTK technology has brought about an era in which one can measure their position with an accuracy of only a few centimeters (a few in) in situations where GPS errors of several meters (several ft) used to be commonplace.

This is a major turning point for construction sites and the surveying industry. On construction sites, RTK GNSS has a large impact on construction management and heavy equipment control; in surveying, it enables the collection of high-precision data for land surveys and construction planning.

In this article, we review the basics and latest trends of RTK GNSS and observe how it is changing construction and surveying sites. At the end, we also introduce a simple procedure to get started with LRTK, a new surveying method that uses these technologies.

What RTK GNSS Is and Why It Matters

Standalone GNSS positioning (such as using only GPS) can produce errors on the order of several meters (several ft) due to ionospheric effects and multipath from buildings and terrain. Therefore, standalone GNSS had limits for construction work and precision surveying that require centimeter-level accuracy (cm level accuracy (half-inch accuracy)).

RTK (Real-Time Kinematic) technology was developed to address this. In RTK, a reference station with a known, accurate coordinate is installed near the site. The reference station determines the difference (error) between the received satellite signals and its known position and sends that error information to the rover.

Because the rover applies the received error corrections to the standalone GNSS positioning data, it can obtain position information on-site with an accuracy on the order of a few centimeters (a few in) in real time. In the past, high-precision surveys required establishing several reference points in the area or post-processing the collected data, but RTK allows immediate high-precision positioning directly on site.

In this way, RTK GNSS breaks technical constraints and provides a step-change in measurement precision, becoming a key technology that significantly alters workflows and management processes on site.

Evolution of GNSS Satellites and Measurement Signals

Recent GNSS technology has advanced toward multi-GNSS use, allowing GPS and GLONASS to be used together with Europe’s Galileo, China’s BeiDou, and Japan’s Quasi-Zenith Satellite System (QZSS, “Michibiki”). Because the number of receivable satellites has increased dramatically, more satellite signals can be captured even in urban or mountainous areas, significantly improving positioning stability and accuracy.

Next-generation GNSS chips can receive multiple frequency signals such as the L5 band simultaneously. By using multi-frequency signals, ionospheric errors can be mitigated, further improving positioning accuracy and reliability.

Furthermore, some satellites broadcast special signals that augment high-precision positioning. For example, Japan’s Michibiki provides CLAS (Centimeter-Level Augmentation Service), which delivers error information generated from the Geospatial Information Authority of Japan’s electronic reference station network directly from satellites on the L6 band. With a compatible receiver, anyone can obtain RTK-like accuracy instantly without additional cost.

By leveraging multiple satellites, multiple frequencies, and new correction signals, the path has opened to reduce GNSS positioning errors that were once limited to several meters down to the centimeter level (cm level accuracy (half-inch accuracy)).

Latest Trends in Error Correction Services That Support RTK

Various technologies have been developed to correct GNSS positioning errors. Representative examples include SBAS (Satellite-Based Augmentation Systems) that use geostationary satellites and DGPS, which sends differential corrections from ground reference stations to reduce errors from meters to several tens of centimeters. However, these methods did not reach centimeter-level accuracy.

Today, RTK is the mainstream correction technology for achieving centimeter-level accuracy on site. RTK correction information is typically sent from the reference station to the rover via UHF radio or cellular communications. Because the correction effect diminishes with distance from the reference station, regional networks of electronic reference stations have been developed and network RTK services such as VRS have been rolled out to provide wide-area corrections.

RTK has required reference station installation and communication links, but a next-generation correction method known as PPP-RTK has recently emerged. In Japan, the aforementioned CLAS is an example; it is a groundbreaking technology that achieves essentially RTK-level accuracy without installing reference stations or communication links.

With PPP-RTK–type corrections, machines and devices at sites in mountainous areas or at sea—where communications are unavailable—can autonomously achieve high-precision positioning, ushering in a new era.

Spread and Cost Reduction of High-Precision Positioning Technology

In the past, centimeter-level GNSS positioning required dedicated high-precision surveying equipment and heavy receivers with large batteries, and investments of several million yen were not uncommon. Today, however, GNSS chips and modules have fallen dramatically in price, and inexpensive GPS modules costing only a few thousand yen are produced in large volumes.

Many people’s smartphones now include high-performance GNSS chips; some Android models support dual-band L1/L5 positioning, and recently Apple has been improving positioning accuracy with its “Precise Location” features. In addition, small GNSS receivers that connect to smartphones via Bluetooth and external GNSS receivers that connect via USB are available on the market.

These developments have reduced the initial cost of using high-precision GNSS, lowering barriers to adoption. General engineers and site personnel can now collect high-precision position data without waiting for specialized contractors. This makes it easier for small construction firms and local governments to perform high-precision surveying in-house without outsourcing.

The government is also promoting ICT use through policies such as “i-Construction,” and smartphone + GNSS–based accuracy improvements and labor savings fit this trend. As these technologies become widespread, on-site digital transformation (DX) accelerates, and each technician will soon be able to leverage high-precision surveying.

RTK Adoption Expands on Construction Sites

On modern construction sites, 3D machine control (3DMC) and 3D machine guidance (3DMG) using heavy equipment equipped with RTK GNSS are now being practically used. By accurately knowing the machine’s position with GNSS while automatically shaping ground elevation and slopes according to digital design data, earthworks are being done faster and with higher quality.

Stakeout work in surveying is also very simple with RTK GNSS. By moving a rover to coordinates specified on the design drawings, you can mark required points. This enables personnel without specialized surveying knowledge to complete stakeout work without errors, greatly reducing physical burdens.

Using RTK GNSS on site can greatly reduce rework and redo work caused by discrepancies between plans and reality. Because work can proceed exactly according to the design, unnecessary burdens from rework or re-surveying disappear, producing significant economic benefits.

Additionally, RTK-capable drones can easily measure post-work terrain, enabling quick calculation of earthwork volumes and early progress assessment. This allows finer site management and reproducible construction management based on data.

Thus, RTK GNSS reduces on-site mistakes and improves safety and productivity. It contributes significantly to addressing labor shortages and shortening construction schedules, and is regarded as an indispensable technology supporting DX in the construction industry.

Transformation and Efficiency Gains in Surveying Work

The spread of high-precision GNSS is also bringing major changes to surveying work. From as-built surveys on construction sites to public surveys and cadastral surveys, RTK GNSS is becoming a routine tool in all kinds of surveying tasks.

Where optical surveying instruments such as total stations or levels once required two-person teams, GNSS and RTK increasingly allow one person to survey wide areas alone. In particularly open sites, a single rover can collect terrain data, and simple topographic surveys that once took several people can sometimes be completed by one person in a few hours.

Moreover, new technologies such as PPP-RTK make it possible to obtain high-precision points in mountainous and out-of-coverage areas, greatly expanding the fieldwork area. Even in remote islands and other distant locations, high-precision data can be collected without worrying about setting up reference points or communication environments, enabling efficient large-area surveys.

As these technologies proliferate, surveying is becoming further digitized. For example, 3D point cloud data that was once difficult to process can now be accurately georeferenced with RTK GNSS; combined with drone photogrammetry and terrestrial LiDAR, design, investigation, and construction are being integrated digitally. RTK GNSS plays an indispensable role in promoting CIM/BIM by enabling the use of large-scale big data.

Easy High-Precision Surveying Enabled by LRTK

So what is the key technology that can turn a smartphone into a full-fledged surveying instrument? One answer is LRTK. LRTK is, simply put, a combination of a tiny RTK positioning device for smartphones and a cloud service that strongly supports GNSS surveying with a smartphone.

The dedicated receiver for LRTK (product name: LRTK Phone) is designed to integrate with a smartphone and weighs only a few hundred grams—comparable to a smartphone—and has a thickness of about 1 cm (0.4 in), making it extremely compact. It contains a high-precision GNSS antenna and a battery and connects wirelessly to the smartphone via Bluetooth, eliminating the need for cables. It can be attached to the back of a smartphone and, when powered on at the site, functions as a GNSS terminal capable of centimeter-level accuracy (cm level accuracy (half-inch accuracy)). It truly realizes a “civil engineering surveying instrument that fits in your pocket.”

With LRTK Phone attached to a smartphone, tasks that formerly required stationary equipment or tripods can be done easily. For example, precise surveys used to require two people operating a total station or carrying a heavy GNSS receiver. With LRTK, you can perform positioning while holding the device in one hand with no complex setup. By tapping “Start Positioning” in the smartphone app, position accuracy converges to the centimeter level within several tens of seconds to about one minute (cm level accuracy (half-inch accuracy)).

In addition, because it supports Japan’s Quasi-Zenith Satellite System and can receive the CLAS satellite augmentation signal, LRTK can perform high-precision GNSS positioning standalone even in sites without cellular coverage, such as mountainous areas. This “usable even out of communications coverage” feature is a major strength for forest surveys and disaster sites.

There are already field examples of LRTK being introduced in civil surveying. For example, in Fukui City, Fukui Prefecture, LRTK Phone was trialed at a 2022 heavy-rain disaster recovery site to speed up surveying. As a result, site staff were able to quickly acquire terrain data of affected areas using an LRTK attached to an iPhone without sending specialist surveyors, aiding recovery work planning (reported by Fukui Broadcasting). Even when communications infrastructure was partially compromised, accurate positioning was achieved using augmentation signals from Michibiki satellites, enabling prompt assessment of isolated disaster sites and data sharing with remote support teams.

LRTK Phone can also be mounted on commercially available monopods or tripods for serious single-point surveying. With a dedicated monopod adapter, the device can be set up like a surveying pole to measure point coordinates. The app automatically calculates the height offset (from the ground to the receiver), eliminating cumbersome correction work. One person can simply hold the pole and press a button to obtain coordinates with accuracy comparable to surveying instruments.

LRTK is designed to fully utilize CLAS, Japan’s satellite augmentation service. By connecting a dedicated “out-of-coverage antenna” and turning on CLAS mode in the app, a fixed solution ("Fix" solution: a solution with errors of a few centimeters (cm level accuracy (half-inch accuracy))) can be obtained from Michibiki in the sky in about 30 seconds to a few minutes. This provides accuracy comparable to conventional RTK without the need for a base station or communication fees. Mastering the latest satellite augmentation services further expands the possibilities of smartphone surveying.

As a result, high-precision surveying—once an area that had to be outsourced—can now be achieved by small construction firms and local governments with minimal initial investment if they have a commercial smartphone and a compact device like LRTK. Because existing smartphones can be reused and LRTK terminals are far cheaper than large receivers, adoption costs are much lower.

"Making high-precision positioning more accessible and easier." LRTK solves GPS error challenges and elevates positioning technology to a new stage. If you are considering construction DX or operational efficiency improvements using GNSS or 3D point cloud data, consider proactively adopting LRTK, a latest-generation high-precision correction technology.

FAQ

Q: What is RTK-GNSS? A: RTK-GNSS refers to technology that corrects GNSS (such as GPS) positioning errors on site in real time to achieve high precision on the order of a few centimeters. By exchanging error information between a reference station and a rover and correcting positions in real time, errors that would be several meters in standalone measurements can be reduced to the order of centimeters.

Q: How accurate is RTK positioning? A: It depends on conditions and environment, but generally RTK results are within about 2–3 cm (0.8–1.2 in) horizontally and about 5–6 cm (2.0–2.4 in) vertically. However, ground GNSS measurements are affected by various factors (multipath, weather), so systematic checks and trial measurements in advance are recommended.

Q: What is required to use RTK? A: Essentially, using RTK requires a reference station with a known accurate position and a rover that collects data. A communication method to connect them (UHF radio or LTE) is also needed. In Japan, however, using reference station networks or services such as the QZSS CLAS can provide high-precision positioning even without local reference stations or communications. Note that a high-precision GNSS receiver is still required in such cases.

Q: What are the benefits of using RTK on construction sites? A: Using RTK on site allows work to proceed according to plan, greatly reducing rework and re-surveying and shortening construction schedules. It also accelerates site DX with benefits such as heavy equipment automatic control and improved safety and security.

Q: What is LRTK? A: LRTK is a solution that consists of a small RTK-GNSS receiver used with a smartphone and a cloud service, enabling anyone to easily perform centimeter-level positioning. Using such a device significantly reduces setup and operation effort on site while allowing the collection of centimeter-level positioning data anywhere, anytime.